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Sandro FIORETTI

Pubblicazioni

Sandro FIORETTI

 

286 pubblicazioni classificate nel seguente modo:

Nr. doc. Classificazioni
150 4 Contributo in Atti di Convegno (Proceeding)
101 1 Contributo su Rivista
25 2 Contributo in Volume
9 5 Altro
1 6 Brevetti
Anno Risorsa
2020 Wavelet Analysis-Based Reconstruction for sEMG Signal Denoising
IFMBE Proceedings
Autore/i: Strazza, A.; Verdini, F.; Mengarelli, A.; Cardarelli, S.; Tigrini, A.; Fioretti, S.; Di Nardo, F.
Editore: Springer
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Surface electromyography (sEMG) recordings provide a safe, easy, and non-invasive method, allowing objective quantification of the electric activity of muscles. Analysis of sEMG plays an important diagnostic role in assessing muscle disorders. Typically, sEMG is a non-stationary signal contaminated by various noises or artifacts that originate at the skin-electrode interface, in the electronics, and in external sources. Thus, appropriate filtering procedures have to be applied to make sEMG clinically usable, in order to extract the main sEMG features. In the recent literatures, among the best performing denoising methods, Wavelet transformation (WT) denoising has been proposed. In particular, aim of this study is to propose a new denoising method based on WT multi-level decomposition analysis. To this aim, Daubechies mother wavelet (4th order, 9 levels of decomposition) was applied to 5 real sEMG tracings. Tibialis anterior (TA) and gastrocnemius lateralis (GL) signals are considered. This method focusses on the choice of a new thresholding rule for sEMG reconstruction and denoising. Performances of this method are computed against soft-thresholding denoising technique (ST) in terms of Root Mean Square Error (RMSE). After application of WT multi-level denoising technique, signal-to-noise ratio (SNR) increased significantly (TA: 14.5 ± 6.9 vs. 19.5 ± 7.1; GL: 14.0 ± 5.4 vs. 18.7 ± 6.3). Moreover, WT multi-level denoising technique showed a lower dispersion than ST (RMSE for TA: 0.8 vs. 1.2; RMSE for GL: 0.9 vs. 1.1.), introduced no sEMG signal delay. Thus, this method is a novel and efficient tool for sEMG denoising, that could be used to make easier the detection of sEMG activation onset-offset.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/282797 Collegamento a IRIS

2020 Variability of muscular recruitment in hemiplegic walking assessed by EMG analysis
ELECTRONICS
Autore/i: Di Nardo, F.; Spinsante, S.; Pagliuca, C.; Poli, A.; Strazza, A.; Agostini, V.; Knaflitz, M.; Fioretti, S.
Classificazione: 1 Contributo su Rivista
Abstract: Adaptive variability during walking is typical of child motor development. It has been reported that neurological disorders could affect this physiological phenomenon. The present work is designed to assess the adaptive variability of muscular recruitment during hemiplegic walking and to detect possible changes compared to control populations. In the attempt of limiting the complexity of computational procedure, the easy-to-measure coefficient of variation (CV) index is adopted to assess surface electromyography (sEMG) variability. The target population includes 34 Winters’ type I and II hemiplegic children (H-group). Two further healthy populations, 34 age-matched children (C-group) and 34 young adults (A-group), are involved as controls. Results show a significant decrease (p < 0.05) of mean CV for gastrocnemius lateralis (GL) in H-group compared to both C-group (15% reduction) and A-group (35% reduction). Reductions of mean CV are detected also for tibialis anterior (TA) in H-group compared to C-group (7% reduction, p > 0.05) and A-group (15% reduction, p < 0.05). Lower CVs indicate a decreased intra-subject variability of ankle-muscle activity compared to controls. Novel contribution of the study is twofold: (1) To propose a CV-based approach for an easy-to-compute assessment of sEMG variability in hemiplegic children, useful in different experimental environments and different clinical purposes; (2) to provide a quantitative assessment of the reduction of intra-subject variability of ankle-muscle activity in mild-hemiplegic children compared to controls (children and adults), suggesting that hemiplegic children present a limited capability of adapting their muscle recruitment to the different stimuli met during walking task. This finding could be very useful in deepening the knowledge of this neurological disorder.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/284183 Collegamento a IRIS

2020 Muscular co-contraction detection: a wavelet coherence approach
IFMBE Proceedings
Autore/i: Strazza, A.; Verdini, F.; Tigrini, A.; Cardarelli, S.; Mengarelli, A.; Fioretti, S.; Di Nardo, F.
Editore: Springer
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Muscular co-contraction is defined as the activity of agonist and antagonist muscles around a joint, enhancing joint stability and balance. The quantitative assessment of muscle co-contractions would be meaningful for deepening the comprehension of this physiological mechanism. Thus, the purpose of this work is to quantify muscle co-contraction using a Wavelet transform-based coherence analysis of sEMG signal during straight walking. To this purpose, sEMG from tibialis anterior (TA) and gastrocnemius lateralis (GL) and basographic signals were acquired in five healthy subjects during walking. Basographic signals were analyzed to quantify foot-floor contact. sEMG signals were processed using Wavelet Transform Coherence (WTC) to identify muscular co-contractions. Daubechies (order 4 with 6 levels of decomposition) was chosen as mother wavelet. A denoising algorithm based on a soft thresholding was applied for removing noise from raw signals. Denoised signals were considered to achieve WTC function, a well-known localized statistical assessment of cross-correlation between signals. Thus, in this work, WTC cross-correlation could be considered to assess muscular co-contraction. This methodology applied to TA and GL signals was able to detect GL/TA co-contractions during hell-strike (0–10% of GC) phase and during P-phase (54.2–68.3% of GC), matching with literature. Moreover, WTC approach was able to provide also the frequency band of information content for muscle co-contractions: 32–65 Hz for H-phase co-contraction and 16–32 Hz for P-phase co-contraction. In conclusion, this study proposed WTC analysis as a reliable method to assess muscle co-contraction in time-frequency domain.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/282798 Collegamento a IRIS

2020 Increased Co-contraction Activity During Push-Off Phase of Walking in Healthy Women
IRBM
Autore/i: Strazza, A.; Mengarelli, A.; Verdini, F.; Cardarelli, S.; Tigrini, A.; Morbidoni, C.; Fioretti, S.; Di Nardo, F.
Classificazione: 1 Contributo su Rivista
Abstract: Research purpose: The assessment of possible gender-related differences in co-contraction activity of quadriceps femoris vs. hamstring muscles in able-bodied adults, during straight walking. Methods: Statistical gait analysis was performed on surface-EMG signals from vastus lateralis (VL), rectus femoris (RF), and medial hamstrings (MH) in 15 female (F-group) and 15 male (M-group) age-matched healthy adults. Co-contraction timing and occurrence frequency were provided. Numerous strides (around 450) were considered for each subject. Results: The same three co-contractions were found in F and M groups, irrespective of gender: during early stance (ES), push-off (PO) and swing (SW) phase. No relevant differences in co-contraction timing were detected between groups. An increase of occurrence frequency was observed in F-group for VL/MH co-activation during PO phase (21.9±13.6% vs. 11.3±8.6% of strides, p=2.5×10−3). Occurrence-frequency value was higher (p=6.9×10−3) in F-group (25.8±12.1%) than in M-group (17.3±14.2%) also for RF/VL co-activation in PO phase. These differences entailed a 74.1% increase of co-contraction events in females (p<0.05) in PO phase. Significance: The present study provides a reference frame for knee-muscle co-contractions during walking, differentiated for women and men. The concomitant analysis of timing and frequency of co-contraction occurrences denotes a significant increase in females of QF/hamstrings co-contraction recruitment in push-off. This suggests a female attempt to augment the level of knee-joint stabilization in the final phase of single support when control of balance is thornier.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/282796 Collegamento a IRIS

2020 Single IMU Displacement and Orientation Estimation of Human Center of Mass: A Magnetometer-Free Approach
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
Autore/i: Cardarelli, Stefano; Mengarelli, Alessandro; Tigrini, Andrea; Strazza, Annachiara; Di Nardo, Francesco; Fioretti, Sandro; Verdini, Federica
Classificazione: 1 Contributo su Rivista
Abstract: In this article, a self-contained procedure to estimate the vertical, medial–lateral, and anterior–posterior displacement of a single sacrum-worn inertial measurement unit (IMU) is presented, which can be related to the human body center of mass (CoM) displacement during treadmill walking through an adaptation of the sacral marker method. Furthermore, a magnetometer-free custom sensor-fusion algorithm for orientation estimation is proposed alongside a practical alignment procedure to refer relative IMU orientation estimation to a ground-fixed reference frame. Twelve healthy subjects performed two trials of treadmill walking at 3, 4, and 5 km/h for 150 s, with a sacrum-worn IMU. Orientation and displacement estimations were then compared with those obtained from an optoelectronic measurement system. Roll, pitch, and yaw angles showed root mean square error (RMSE) lower than 2° for walking trials at 3, 4, and 5 km/h, with Pearson’s correlation coefficient higher than 0.90 for each angle. Displacement accuracy was evaluated in terms of peak-to-trough distances and RMSE. Mean errors resulted lower than 1 mm for each axis of interest and for each gait speed, with RMSE not higher than 2.5 mm. The proposed off-line algorithm can be used in low-budget and infrastructure-free environments, to achieve reliable CoM displacement estimation during cyclic activities such as treadmill walking.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/283223 Collegamento a IRIS

2020 Recognition of gait phases with a single knee electrogoniometer: A deep learning approach
ELECTRONICS
Autore/i: Di Nardo, F.; Morbidoni, C.; Cucchiarelli, A.; Fioretti, S.
Classificazione: 1 Contributo su Rivista
Abstract: Artificial neural networks were satisfactorily implemented for assessing gait events from different walking data. This study aims to propose a novel approach for recognizing gait phases and events, based on deep-learning analysis of only sagittal knee-joint angle measured by a single electrogoniometer per leg. Promising classification/prediction performances have been previously achieved by surface-EMG studies; thus, a further aim is to test if adding electrogoniometer data could improve classification performances of state-of-the-art methods. Gait data are measured in about 10,000 strides from 23 healthy adults, during ground walking. A multi-layer perceptron model is implemented, composed of three hidden layers and a one-dimensional output. Classification/prediction accuracy is tested vs. ground truth represented by foot–floor-contact signals, through samples acquired from subjects not seen during training phase. Average classification-accuracy of 90.6 ± 2.9% and mean absolute value (MAE) of 29.4 ± 13.7 and 99.5 ± 28.9 ms in assessing heel-strike and toe-off timing are achieved in unseen subjects. Improvement of classification-accuracy (four points) and reduction of MAE (at least 35%) are achieved when knee-angle data are used to enhance sEMG-data prediction. Comparison of the two approaches shows as the reduction of set-up complexity implies a worsening of mainly toe-off prediction. Thus, the present electrogoniometer approach is particularly suitable for the classification tasks where only heel-strike event is involved, such as stride recognition, stride-time computation, and identification of toe walking.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/282795 Collegamento a IRIS

2020 Co-activation of Knee Muscles in Female vs. Male Adults
IFMBE Proceedings
Autore/i: Di Nardo, F.; Strazza, A.; Tigrini, A.; Mascia, G.; Cardarelli, S.; Mengarelli, A.; Verdini, F.; Fioretti, S.
Editore: Springer
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: During walking, knee joint mechanics is primarily regulated by thigh-muscle group, i.e. hamstrings and quadriceps femoris. Research purpose was to assess gender-related differences in concomitant recruitment of antagonist knee-joint muscles during ground walking. To this aim, Statistical gait analysis was performed on surface-electromyographic (sEMG) signals from vastus lateralis (VL) and medial hamstrings (MH) in 15 female (F-group) and 15 male (M-group) age-matched able-bodied young adults. sEMG signals from numerous strides (average value ± SD of 452 ± 102 strides for F-group and 440 ± 106 strides for M-group) were analyzed for each subject. Results showed that the same three VL/MH co-activations were found in the gait cycle, irrespective of gender: during early stance (ES), push-off (PO), and swing (SW) phase. No significant gender-related differences (p > 0.05) were observed in co-activity duration. Differently, an increase of occurrence frequency was observed in F-group for VL/MH co-activation during PO phase, with respect to M-group (21.9 ± 13.6% vs. 11.3 ± 8.6% of strides, p = 2.5 × 10−3). This increased occurrence of co-activations suggests a more complex muscular recruitment for knee-joint stabilization in females, in particular in PO phase when the control of balance is more awkward because of the final phase of single support. In conclusion, the present study indicates gender as a not negligible factor in evaluating knee-muscle co-activation during walking.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/282799 Collegamento a IRIS

2020 On the use of fuzzy and permutation entropy in hand gesture characterization from EMG signals: Parameters selection and comparison
APPLIED SCIENCES
Autore/i: Mengarelli, A.; Tigrini, A.; Fioretti, S.; Cardarelli, S.; Verdini, F.
Classificazione: 1 Contributo su Rivista
Abstract: The surface electromyography signal (sEMG) is widely used for gesture characterization; its reliability is strongly connected to the features extracted from sEMG recordings. This study aimed to investigate the use of two complexity measures, i.e., fuzzy entropy (FEn) and permutation entropy (PEn) for hand gesture characterization. Fourteen upper limb movements, sorted into three sets, were collected on ten subjects and the performances of FEn and PEn for gesture descriptions were analyzed for different computational parameters. FEn and PEn were able to properly cluster the expected numbers of gestures, but computational parameters were crucial for ensuring clusters’ separability and proper gesture characterization. FEn and PEn were also compared with other eighteen classical time and frequency domain features through the minimum redundancy maximum relevance algorithm and showed the best predictive importance scores in two gesture sets; they also had scores within the subset of the best five features in the remaining one. Further, the classification accuracies of four different feature sets presented remarkable increases when FEn and PEn are included as additional features. Outcomes support the use of FEn and PEn for hand gesture description when computational parameters are properly selected, and they could be useful in supporting the development of robotic arms and prostheses myoelectric control.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/284707 Collegamento a IRIS

2020 Functional evaluation of triceps surae during heel rise test: from EMG frequency analysis to machine learning approach
MEDICAL & BIOLOGICAL ENGINEERING & COMPUTING
Autore/i: Ferracuti, Francesco; Fioretti, Sandro; Frontoni, Emanuele; Iarlori, Sabrina; Mengarelli, Alessandro; Riccio, Michele; Romeo, Luca; Verdini, Federica
Classificazione: 1 Contributo su Rivista
Abstract: Soleus muscle flap as coverage tissue is a possible surgical solution adopted to cover the wounds due to open fractures. Despite this procedure presents many clinical advantages, relatively poor information is available about the loss of functionality of triceps surae of the treated leg. In this study, a group of patients who underwent a soleus muscle flap surgical procedure has been analyzed through the heel rise test (HRT), in order to explore the triceps surae residual functionalities. A frequency band analysis was performed in order to assess whether the residual heads of triceps surae exhibit different characteristics with respect to both the non-treated lower limb and an age-matched control group. Then, an in-depth analysis based on a machine learning approach was proposed for discriminating between groups by generalizing across new unseen subjects. Experimental results showed the reliability of the proposed analyses for discriminating between-group at a specific time epoch and the high interpretability of the proposed machine learning algorithm allowed the temporal localization of the most discriminative frequency bands. Findings of this study highlighted that significant differences can be recognized in the myoelectric spectral characteristics between the treated and contralateral leg in patients who underwent soleus flap surgery. These experimental results may support the clinical decision-making for assessing triceps surae performance and for supporting the choice of treatment in plastic and reconstructive surgery.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/286181 Collegamento a IRIS

2020 Kinetic data simultaneously acquired from dynamometric force plate and Nintendo Wii Balance Board during human static posture trials
DATA IN BRIEF
Autore/i: Mengarelli, A.; Cardarelli, S.; Tigrini, A.; Fioretti, S.; Verdini, F.
Classificazione: 1 Contributo su Rivista
Abstract: Data provided with this article are relative to kinetic measures from standing posture trials in eye open and eye closed conditions of 15 healthy subjects, acquired from a dynamometric force plate and a Nintendo Wii Balance Board (NBB). Data have been originally collected for a research project aimed at evaluating the reliability of low-cost devices in clinical scenarios. Raw data from the force plate include three ground reaction force components, center of pressure trajectories and torque around the vertical axis. Raw data from the NBB consist of vertical component of the ground reaction force measured by each of the four device sensors. Processed data consist of synchronized center of pressure time-series from both devices, referred to the force plate reference frame. Data were acquired simultaneously from the devices, allowing a direct comparison between the kinetic measures provided by the gold-standard for posture analysis (dynamometric force plate) and a low-cost device (NBB). Utility of present data can be twofold: first they can be used to assess the overall quality of the NBB signals for posturographic analysis by a direct comparison with the same signals acquired from the gold-standard device for kinetic measurement. Secondly, data from the dynamometric force plate can be used per se to evaluate different kind of parameters useful to assess balance capabilities, also by comparing data from different sensorial conditions (eye open versus eye closed).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273466 Collegamento a IRIS

2019 An interactive tool for the analysis of muscular recruitment during walking task
COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING: IMAGING & VISUALIZATION
Autore/i: MENGARELLI, ALESSANDRO; CARDARELLI, STEFANO; DI NARDO, Francesco; BURATTINI, Laura; VERDINI, Federica; FIORETTI, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: The present work proposes an interactive software tool for surface electromyography signal processing and analysis, focused on the assessment of muscular activations during walking and easy-to-use also for users without signal treatment knowledge. The tool is based on two logical steps: first, an automatic detection of muscle activations is provided; then, the user can tune the value of each processing parameter, with a real-time visual feedback. A stride-to-stride evaluation of muscular recruitment and a co-contraction recognition are available, together with the computation of an average myoelectric activation pattern. The tunable signal processing tailors the analysis to any considered application, allowing to extract information from low-quality signals. A muscle activity characterisation from the single stride to the whole walking trial is also provided. Beyond gait analysis and muscles activation timing identification, this tool could be valuable also in an educational scenario, considering the interactive characteristics of the graphical user interface.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260812 Collegamento a IRIS

2019 Wavelet filtering of fetal phonocardiography: A comparative analysis
MATHEMATICAL BIOSCIENCES AND ENGINEERING
Autore/i: Tomassini, S.; Strazza, A.; Sbrollini, A.; Marcantoni, I.; Morettini, M.; Fioretti, S.; Burattini, L.
Classificazione: 1 Contributo su Rivista
Abstract: Fetal heart rate (FHR) monitoring can serve as a benchmark to identify high-risk fetuses. Fetal phonocardiogram (FPCG) is the recording of the fetal heart sounds (FHS) by means of a small acoustic sensor placed on maternal abdomen. Being heavily contaminated by noise, FPCG processing implies mandatory filtering to make FPCG clinically usable. Aim of the present study was to perform a comparative analysis of filters based on Wavelet transform (WT) characterized by different combinations of mothers Wavelet and thresholding settings. By combining three mothers Wavelet (4th-order Coiflet, 4th-order Daubechies and 8th-order Symlet), two thresholding rules (Soft and Hard) and three thresholding algorithms (Universal, Rigorous and Minimax), 18 different WT-based filters were obtained and applied to 37 simulated and 119 experimental FPCG data (PhysioNet/PhysioBank). Filters performance was evaluated in terms of reliability in FHR estimation from filtered FPCG and noise reduction quantified by the signal-to-noise ratio (SNR). The filter obtained by combining the 4th-order Coiflet mother Wavelet with the Soft thresholding rule and the Universal thresholding algorithm was found to be optimal in both simulated and experimental FPCG data, since able to maintain FHR with respect to reference (138.7[137.7; 140.8] bpm vs. 140.2[139.7; 140.7] bpm, P > 0.05, in simulated FPCG data; 139.6[113.4; 144.2] bpm vs. 140.5[135.2; 146.3] bpm, P > 0.05, in experimental FPCG data) while strongly incrementing SNR (25.9[20.4; 31.3] dB vs. 0.7[−0.2; 2.9] dB, P < 10-14, in simulated FPCG data; 22.9[20.1; 25.7] dB vs. 15.6[13.8; 16.7] dB, P < 10-37, in experimental FPCG data). In conclusion, the WT-based filter obtained combining the 4th-order Coiflet mother Wavelet with the thresholding settings constituted by the Soft rule and the Universal algorithm provides the optimal WT-based filter for FPCG filtering according to evaluation criteria based on both noise and clinical features.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/269344 Collegamento a IRIS

2019 PCG-Decompositor: A New Method for Fetal Phonocardiogram Filtering Based on Wavelet Transform Multi-level Decomposition
IFMBE Proceedings
Autore/i: Strazza, A.; Sbrollini, A.; Olivastrelli, M.; Piersanti, A.; Tomassini, S.; Marcantoni, I.; Morettini, M.; Fioretti, S.; Burattini, L.
Editore: Springer
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Fetal phonocardiography (FPCG) is a non-invasive acoustic recording of fetal heart sounds (fHS). The fHS auscultation plays an important diagnostic role in assessing fetal wellbeing. Typically, FPCG is a non-stationary signal corrupted by the presence of noise. Thus, high-amplitude noise makes detection of FPCG waveforms challenging. Thus, appropriate filtering procedures have to be applied in order to make FPCG clinically usable. In the recent years, Wavelet transformation (WT) filtering has been proposed. In particular, aim of this study is to propose a new method based on WT multi-level decomposition filtering: PCG-Decompositor. To this aim, PCG-Decompositor based on Coiflets mother Wavelet (4th order, 9 levels of decomposition) was applied to 119 real FPCG tracings, all available in Physionet. PCG-Decompositor is a dependent thresholding technique based on FPCG multi-level decomposition analysis. Performances of PCG-Decompositor are computed against soft-thresholding denoising technique (STDT) in terms of Root Mean Square Error (RMSE) and fetal heart rate (fHR). In terms of fHR, PCG-Decompositor and STDT are compared between themselves and also with the so-called annotations, given by the average fHR using a simultaneous cardiotocography analysis. Original signal to noise ratio (SNR) values ranged from 7.1 dB to 24.4 dB; after application of PCG-Decompositor, SNR increased significantly, ranging from 9.7 dB to 26.9 dB (P < 10−7). Moreover, PCG-Decompositor showed a lower dispersion than STDT (RMSE: 0.7 dB vs. 1.2 dB), introduced no FPCG signal delay and left fHR unaltered. Thus, PCG-Decompositor could be a suitable and robust technique to denoise FPCG signals.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272507 Collegamento a IRIS

2019 Role of the Ground Reaction Force Components in Balance Assessment during Squatting Exercise performed by the Wii Balance Board
2019 IEEE 23rd International Symposium on Consumer Technologies, ISCT 2019
Autore/i: Mengarelli, A.; Tigrini, A.; Marchesini, L.; Strazza, A.; Fioretti, S.; Cardarelli, S.; Verdini, F.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The Nintendo Wii Balance Board (WBB) has been proposed as a valid low-cost device for the assessment of balance in many different motor tasks. However, the direct comparisons with the gold-standard for balance measure represented by the laboratory grade force plates (FP) showed fixed biases affecting both the center of pressure (CoP) computation and its related spatial parameters, which can be partially attributed to the negligence of horizontal ground reaction force (HGRF) components in WBB-CoP computation. Thus, this study aimed to quantify to what extent the absence of HGRF affects the errors between FP and WBB in CoP related parameters during the squatting movement, where significant HGRFs are involved. Results showed that the HGRF negligence affects errors between FP and WBB to a significantly different extent when squat exercise is performed with two different techniques, being higher when squatting does not reach the maximal depth (average value of 60% versus 40% for all the considered parameters). Outcomes of this study seem to indicate that the use of WBB could be preferable for motor task with a marked mono-axial dynamics and in particular for the squatting exercise performed with a high squatting depth.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272459 Collegamento a IRIS

2019 Magnetometer-Free Sensor Fusion Applied to Pedestrian Tracking: A Feasibility Study
2019 IEEE 23rd International Symposium on Consumer Technologies, ISCT 2019
Autore/i: Cardarelli, S.; Di Florio, P.; Mengarelli, A.; Tigrini, A.; Fioretti, S.; Verdini, F.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In this paper a feasibility study on magnetometer-free sensor fusion in 2D pedestrian position and orientation tracking is presented. The sensor-fusion is performed through a nonlinear Kalman filter variant. The estimated orientation is then used to properly refer measured acceleration in an arbitrarily chosen navigation reference frame. Also, the same data is used to accurately remove the gravitational component from the measurement acceleration before any integration procedure to yield velocity and position. n addition, a custom curve for accurate foot-stance recognition is proposed. A velocity and acceleration reset is performed on the instants recognized thanks to the proposed time series. Estimated position of the foot-mounted IMU is then compared with fixed landmarks. Three walking tasks have been performed: a circle, a square and a longer indoor walk. Results show good accuracy in spite of the absence of heading information coming from the magnetometer (errors below 10 cm for the short trials), although on the long distances drift is more evident (2 m over 48 m of overall walking distance covered). Finally, a series of random walks have been performed to evaluate the foot stance recognition using the proposed time series against the simple accelerometer module evaluation.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272460 Collegamento a IRIS

2019 Validation of a Gait Analysis Algorithm for Wearable Sensors
International Symposium on Sensors and Instrumentation in Internet of Things Era (ISSI)
Autore/i: Pierleoni, Paola; Belli, Alberto; Palma, Lorenzo; Mercuri, Marco; Verdini, Federica; Fioretti, Sandro; Madgwick, Sebastian; Pinti, Federica
Editore: IEEE
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The world population ageing and the increase of health costs make necessary the development of new technologies and IoT solutions. Smart and wearable systems can improve people's lives, monitoring the elderly and transforming everyday living environments into more connected and sustainable systems. Due to ageing, people tend to suffer more and more from motor problems, so gait analysis is fundamental for many medical and health applications. In this paper, we propose a wearable sensors system for gait analysis constituted of a triaxial accelerometer, gyroscope, and magnetometer with efficient gait analysis algorithms. In this study we have developed an algorithm for the estimation of percentage duration of double support, stride length and stride speed. The results obtained from comparison with the gold standard show errors of 4.3 % for double support duration, 5.9 % for stride length, and 6.3 % for stride speed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/271172 Collegamento a IRIS

2019 Inertial Sensor Based Estimation of the Center of Pressure during Unperturbed Upright Stance
2019 IEEE 23rd International Symposium on Consumer Technologies, ISCT 2019
Autore/i: Mengarelli, A.; Cardarelli, S.; Tigrini, A.; Marchesini, L.; Strazza, A.; Fioretti, S.; Verdini, F.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The unperturbed upright stance is considered one of the most important task for evaluating active and passive control of balance. In this field, the analysis of the center of pressure (COP) displacement is a valuable source of information for extracting and evaluating postural features in healthy and pathological subjects. COP is commonly measured by dynamometric force plates (DFP), which represent the gold-standard for measuring dynamic quantities. However, the availability of DFP is often limited by their cost and by the need for instrumented environments. In the past few years, inertial measurement units (IMU) have been proposed for estimating ground reaction forces and torques during selected motor tasks and under specific experimental conditions. Therefore, the aim of this study was to propose a novel method for deriving COP displacement during unperturbed posture by using a single sacrum-worn IMU. Results showed a remarkable correspondence between estimated COP time-series and those measured simultaneously by a DFP (root mean square error not beyond 1.5 mm, with a correlation not under 0.98). Further, the COP mean distance presented biases which are below 2 mm for both anterior-posterior and medial-lateral COP components, with the absence of any tendency towards proportional errors. Outcomes of this study seem to suggest the reliability of a single IMU based method for estimating COP displacement during balance maintenance task, providing a low-cost and unobtrusive procedure suitable for those contexts where classical motion analysis instrumentation is hardly or totally unavailable.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272458 Collegamento a IRIS

2019 Evaluation of a New Wearable Technology for Kinematic Analysis during Perturbed Posture
2019 IEEE 23rd International Symposium on Consumer Technologies, ISCT 2019
Autore/i: Verdini, F.; Gianferrari, F.; Raggi, M.; Mengarelli, A.; Cardarelli, S.; Tigrini, A.; Di Nardo, F.; Di Florio, P.; Fioretti, S.; Ligorio, G.; Garofalo, P.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In this study a validity evaluation of a sensorized, full-body suit for kinematic measurement during perturbed upright stance task was proposed. Subjects underwent to a series of translational perturbations of the base of support in backward direction, with fixed speed and space (20 cm/s, 15 cm), The ankle joint angular displacement were simultaneously acquired by the full-body suit and an optoelectronic system, considered as the gold-standard for kinematics measurement. The two devices showed a good correspondence between measures, with absolute biases not higher than 0.8 degrees for both ankle joint range of motion and peaks amplitude. Results suggest the possibility to use the proposed wearable technology for assessing human body angular kinematics during perturbed posturography trials, in order to analyze balance strategies employed for external disruption withstanding and balance recovery.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272456 Collegamento a IRIS

2019 Fifty Years of Biomedical Engineering: From Origin to Smart Technologies
The First Outstanding 50 Years of "Università Politecnica delle Marche"
Autore/i: Burattini, Laura; Di Nardo, Francesco; Morettini, Micaela; Verdini, Federica; Fioretti, Sandro
Classificazione: 2 Contributo in Volume
Abstract: In Italy, the Bioengineering Community was founded in 1980. The kick-off meeting was held in Montesicuro, a little village near Ancona and organized by Prof. Tommaso Leo from the then-named “Università degli Studi di Ancona” (now Università Politecnica delle Marche, UNIVPM) in cooperation with the nascent National Group of Bioengineering. This chapter aims to produce a brief review of the main results in Biomedical Engineering by UNIVPM during the first 50 years useful to understand the present and to track future contributions for the next 50 years. It is also an occasion to recall the pioneering work on the Bioengineering of the Neuromuscular, Cardiovascular and Metabolic systems performed by our leading colleagues Tommaso Leo, Paolo Mancini and Roberto Burattini, as well as to describe significant research achievements obtained by professors, researchers, post-doc fellows and PhD students who worked and/or are currently working at the UNVPM. Though mainly focusing on research findings in the above cited physiological systems, it is also worth mentioning in this chapter that UNIVPM has also an educational mission, provided by the two Biomedical Engineering courses currently active at the Engineering Faculty: the three-year Bachelor and the two-year Master (in English) courses.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/278101 Collegamento a IRIS

2019 Description of Postural Strategies through a Variable Structure Control
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Tigrini, A.; Mengarelli, A.; Cardarelli, S.; Strazza, A.; Di Nardo, F.; Fioretti, S.; Verdini, F.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Human postural strategies in balance maintenance are the results of the complex control action played by the Central Nervous System (CNS). Literature underlined that such strategies become more evident when external perturbations challenge the stance. In this study, a new model of balance maintenance under support base movement perturbation is formulated. A sliding mode approach is employed to simulate the aforementioned strategies in stabilizing a double inverted pendulum, used to describe the mechanics of the bipedal human stance. Control parameters are then optimized in order to reproduce the measured center of mass (COM) displacement in the anterior-posterior direction. Such parameters seem to be useful to distinguish different postural strategies employed by different subjects. Moreover, electromyographic data are employed to effectively support the goodness of the model.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/275282 Collegamento a IRIS

2019 Complexity Measures of Postural Control in Type-2 Diabetic Subjects
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Mengarelli, A.; Verdini, F.; Cardarelli, S.; Tigrini, A.; Strazza, A.; Di Nardo, F.; Anna Rabini, R.; Mercante, O.; Fioretti, S.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Balance maintenance is commonly analyzed by evaluating the center of pressure (COP) displacement, which presents an acknowledged non-stationary behavior. The latter led to an evaluation of COP regularity through complexity measures such as the approximate (AppEn) and sample entropy (SampEn). These indexes quantify the regularity of time-series in terms of inner pattern recurrence; however, they are highly dependent on the input parameters used for their computation. Thus, this study aimed to evaluate the use of the AppEn, SampEn and a recently proposed entropy measure, the fuzzy entropy (FuzzyEn) for the analysis of COP time-series in type-2 diabetic subjects with and without neuropathy during quiet standing trials in eyes open condition. Results highlighted consistency of entropy measures for different values of input parameters, showing significant differences between the two populations in terms of COP regularity for both anterior-posterior and medial-lateral directions. Findings of this study outline low complexity in postural control of neuropathic subjects, also in the medial-lateral direction, which could indicate a limited capacity of producing adaptable responses, relying on fixed balance control patterns. Further, they support the use of complexity measures for the analysis of patients with diabetic neurological impairment.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/275283 Collegamento a IRIS

2019 Fractal Analysis of Motor Control in Knee Arthroplasty Patients
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Mengarelli, A.; Cardarelli, S.; Tigrini, A.; Strazza, A.; Di Nardo, F.; Marchesini, L.; Fioretti, S.; Verdini, F.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Knee osteoarthritis is commonly treated through total knee arthroplasty (TKA) or unicompartmental knee arthroplasty (UKA) and therefore the assessment of postoperative differences in functional capabilities between TKA and UKA patients appears of primary importance. Throughout the years, fractal analysis has been applied to several biological time-series, revealing to be particularly useful for assessing human balance and motor control by quantifying complexity and repeatability of dynamic measures. In this study, fractal dimension (FD) has been computed on ground reaction force and momentum acquired during squatting movement in two groups of TKA and UKA patients and a control group of healthy subjects (CTRL). FD resulted able to discriminate between TKA and both CTRL and UKA group, showing significant differences in all the considered measures. Outcomes of this study could help to gain further information about functional recovery after different knee arthroplasty procedures, in order to improve the choice of rehabilitative treatment.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273470 Collegamento a IRIS

2019 Modeling Perturbed Posture Through An Adaptive Sliding Mode Approach
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Tigrini, A.; Mengarelli, A.; Cardarelli, S.; Strazza, A.; Di Nardo, F.; Fioretti, S.; Verdini, F.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Upright stance maintenance under perturbed condition is a complex phenomenon in which the Central Nervous System(CNS) is engaged to regulate the balance preventing subject to fall. Many models of unperturbed stance are present in literature. However, the necessity to model balance maintenance in presence of external disturbance is still an open problem. In this paper, a new model representing the human balance maintenance under perturbed condition is presented. An adaptive sliding mode approach is used to model the action played by the CNS, the control parameters are then optimized in order to match real and simulated data. The trend of optimized parameters seems to reveal the development of different postural strategies throughout the experimental trials.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273469 Collegamento a IRIS

2019 UKF Magnetometer-Free Sensor Fusion for Pelvis Pose Estimation During Treadmill Walking
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Cardarelli, S.; Mengarelli, A.; Tigrini, A.; Strazza, A.; Di Nardo, F.; Verdini, F.; Fioretti, S.
Editore: NLM (Medline)
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Inertial measurement units are an efficient tool to estimate the orientation of a rigid body with respect to a global or navigation frame. Thanks to their relatively small scale, these devices are often employed in clinical environments in form of wearable devices. A direct consequence of this large use of inertial sensors has been the development of many sensor fusion techniques for pose estimation in many practical applications. In this paper we study the feasibility of a nonlinear "Unscented" variant of the well-known Kalman Filter for gyroscope/accelerometer sensor fusion in pelvis pose estimation during treadmill walking. In addition, orientation estimation has been obtained without IMU magnetometer data, in order to propose a method suitable also for environments where magnetic disturbances could arise. Pelvis heading (yaw), bank (roll) and attitude (pitch) angles have been evaluated both using the proposed filter and a gold standard optometric system. The root mean square errors obtained using the proposed sensor fusion with respect to the gold standard are below 1 degree for each axis, showing also a significant high correlation (> 0.90). Findings of this study highlight the suitability of a magnetometer-free UKF approach for pose estimation of pelvis during human walking on treadmill, providing information useful also for further estimation of center of mass displacement in the same experimental conditions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273471 Collegamento a IRIS

2019 EMG-based characterization of walking asymmetry in children with mild hemiplegic cerebral palsy
BIOSENSORS
Autore/i: Di Nardo, F.; Strazza, A.; Mengarelli, A.; Cardarelli, S.; Tigrini, A.; Verdini, F.; Nascimbeni, A.; Agostini, V.; Knaflitz, M.; Fioretti, S.
Classificazione: 1 Contributo su Rivista
Abstract: Hemiplegia is a neurological disorder, detected in children with cerebral palsy. Although many studies investigated muscular activity in hemiplegic leg, few EMG-based findings focused on unaffected limb. The study aimed to quantify the asymmetric behavior of lower-limb-muscle recruitment during walking in mild-hemiplegic children from surface-EMG and foot-floor-contact features. sEMG signals from tibialis anterior (TA) and gastrocnemius lateralis and foot-floor-contact data during walking were analyzed in 16 hemiplegic children classified as W1 according to Winter’ scale, and in 100 control children. Statistical gait analysis, a methodology achieving a statistical characterization of gait by averaging surface-EMG-based features, was performed. Results, achieved in hundreds of strides for each child, indicated that in hemiplegic side with respect to non-hemiplegic side, W1 children showed a statistically significant: decreased number of strides with normal foot-floor contact; decreased stance-phase length and initial-contact sub-phase; curtailed, less frequent TA activity in terminal swing and a lack of TA activity at heel-strike. The acknowledged impairment of anti-phase eccentric control of dorsi-flexors was confirmed in hemiplegic side, but not in contralateral one. However, a modified foot-floor-contact pattern is evinced also in the contralateral side, probably to make up for balance requirements.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/270354 Collegamento a IRIS

2019 Glucose effectiveness and its components in relation to body mass index
EUROPEAN JOURNAL OF CLINICAL INVESTIGATION
Autore/i: Morettini, M.; Di Nardo, F.; INGRILLINI, LAURA; Fioretti, S.; Gobl, C.; Kautzky-Willer, A.; TURA, ANDREA; PACINI, GIOVANNI; Burattini, L.
Classificazione: 1 Contributo su Rivista
Abstract: Background: Obesity is known to induce a deterioration of insulin sensitivity (SI), one of the insulin-dependent components of glucose tolerance. However, few studies investigated whether obesity affects also the insulin-independent component, that is glucose effectiveness (SG). This cross-sectional study aimed to analyse SG and its components in different body mass index (BMI) categories. Materials and methods: Three groups of subjects spanning different BMI (kg m−2) categories underwent a 3-h frequently sampled intravenous glucose tolerance test: Lean (LE; 18.5 ≤ BMI < 25, n = 73), Overweight (OW; 25 ≤ BMI < 30, n = 90), and Obese (OB; BMI ≥ 30, n = 41). OB has been further divided into two subgroups, namely Obese I (OB-I; 30 ≤ BMI < 35, n = 27) and Morbidly Obese (OB-M; BMI ≥ 35, n = 14). Minimal model analysis provided SG and its components at zero (GEZI) and at basal (BIE) insulin. Results: Values for SG were 1.98 ± 1.30 × 10−2·min−1 in all subjects grouped and 2.38 ± 1.23, 1.84 ± 0.82, 1.59 ± 0.61 10−2·min−1 in LE, OW and OB, respectively. In all subjects grouped, a significant inverse linear correlation was found between the log-transformed values of SG and BMI (r = −0.3, P < 0.0001). SG was significantly reduced in OW and OB with respect to LE (P < 0.001) but no significant difference was detected between OB and OW (P = 0.35) and between OB-I and OB-M (P = 0.25). Similar results were found for GEZI. BIE was not significantly different among NW, OW and OB (P = 0.11) and between OB-I and OB-M (P ≥ 0.07). Conclusions: SG and its major component GEZI deteriorate in overweight individuals compared to those in the normal BMI range, without further deterioration when BMI increases above 30 kg m−2.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/267129 Collegamento a IRIS

2019 A deep learning approach to EMG-based classification of gait phases during level ground walking
ELECTRONICS
Autore/i: Morbidoni, C.; Cucchiarelli, A.; Fioretti, S.; Di Nardo, F.
Classificazione: 1 Contributo su Rivista
Abstract: Correctly identifying gait phases is a prerequisite to achieve a spatial/temporal characterization of muscular recruitment during walking. Literature reported few machine-learning-based approaches for gait-phases classification from surface electromyographic (sEMG) signal during treadmill walking. To our knowledge, no attempts were made during ground walking in daily-life conditions. A methodology for classification of stance/swing and prediction of foot-floor-contact signal during ground walking in conditions similar to daily life is proposed here, based on the application of Multi-Layer Perceptron models to sEMG signal alone. sEMG were acquired from eight lower-limb muscles in about 13.000 strides from 23 healthy adults, during ground walking, following an eight-shaped path including natural deceleration, reversing, curve, and acceleration. Classification and prediction accuracy were tested vs. the ground truth, represented by the basographic signal provided by three foot-switches, through samples not used in the learning phase, coming from both the same group of subjects used to generate the learning set (LS-Test) and brand-new subjects (unlearned, US). Results showed an average classification accuracy (± SD) over 23 folds of 94.9 ± 0.3 for LS-test and 93.4 ± 2.3 for US. Prediction of foot-floor-contact signal was quantified in terms of timing of heel strike and toe off: mean (over ten folds) absolute difference between predictions and footswitch data for UL was 15 ± 17 ms and 36 ± 22 ms for heel-strike and toe off, respectively. The suitable performance achieved by the proposed method suggests that it could be successfully used to automatically classify gait phases and predict foot-floor-contact signal from sEMG signals during ground walking in daily-life conditions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/270351 Collegamento a IRIS

2018 Surface electromyography low-frequency content: Assessment in isometric conditions after electrocardiogram cancellation by the Segmented-Beat Modulation Method
INFORMATICS IN MEDICINE UNLOCKED
Autore/i: Sbrollini, Agnese; Strazza, Annachiara; Candelaresi, Silvia; Marcantoni, Ilaria; Morettini, Micaela; Fioretti, Sandro; Di Nardo, Francesco; Burattini, Laura
Classificazione: 1 Contributo su Rivista
Abstract: Background: Surface electromyography (SEMG) is widely used in clinics for assessing muscle functionality. All procedures proposed for noise reduction alter SEMG spectrum, especially in the low-frequency band (below 30 Hz). Indeed, low-frequency band is generally addressed to motion artifacts and electrocardiogram (ECG) interference without any further investigation on the possibility of SEMG having significant spectral content. The aim of the present study was evaluating SEMG frequency content to understand if low-frequency spectral content is negligible or, on the contrary, represents a significant SEMG portion potentially providing relevant clinical information. Method: Isometric recordings of five muscles (sternocleidomastoideus, erectores spinae at L4, rectus abdominis, rectus femoris and tibialis anterior) were acquired in 10 young healthy voluntary subjects. These recordings were not affected by motion artifacts by construction and were pre-processed by the Segmented-Beat Modulation Method for ECG deletion before performing spectral analysis. Results: Results indicated that SEMG frequency content is muscle and subject dependent. Overall, the 50th[25th;75th] percentiles spectrum median frequency and spectral power below 30 Hz were 74[54; 87] Hz and 18[10; 31] % of total (0–450 Hz) spectral power. Conclusions: Low-frequency spectral content represents a significant SEMG portion and should not be neglected.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/262204 Collegamento a IRIS

2018 Role of the visual feedback on balance responses to upright stance perturbations
IFMBE Proceedings
Autore/i: Mengarelli, Alessandro; CARDARELLI, STEFANO; FIORETTI, Sandro; STRAZZA, ANNACHIARA; TIGRINI, ANDREA; DI NARDO, Francesco; BURATTINI, Laura; VERDINI, Federica
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Abstract: In this study an evaluation of visual feedback on the balance response to upright stance perturbations is proposed. Subjects underwent to base of support translations in backward direction at fixed velocity in an eye-open (EO) and eye-closed (EC) condition. Center of pressure (COP) and center of mass (COM) were acquired, showing a repeatable double-peak shape which mirrors two different response periods: a destabilizing phase and a counterbalancing phase. Thus, COP and COM were analyzed on the basis of their temporal and spatial features. Further, also the angular displacement of lower limb joints, trunk and head were considered and lower limb muscular activity in terms of myoelectric latencies. Results showed several differences in COP and COM based parameters between EO and EC condition. Moreover, angular range variations seemed to indicate a different role of each joint in the two considered sensory conditions, highlighting the switch from an ankle-based strategy (EO condition) to a more complex kinematic strategy (EC condition). Outcomes of this study could add information about: (A) the suitability of considering COP displacement in perturbed posture analyses with sensory deprivation and (B) the significant role of the visual feedback in balance maintenance when a sudden and quasi-impulsive disruption is employed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260809 Collegamento a IRIS

2018 A sliding mode control model for perturbed upright stance in healthy subjects
IFMBE Proceedings
Autore/i: MENGARELLI, ALESSANDRO; FIORETTI, Sandro; ORLANDO, Giuseppe; CARDARELLI, STEFANO; ISMAELE, FIORETTI; Marco Paci, Gian; BURATTINI, Laura; DI NARDO, Francesco; STRAZZA, ANNACHIARA; VERDINI, Federica
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Abstract: Human upright stance and balance maintenance in quiet conditions have been extensively evaluated throughout the years. However, relatively less information is available on how the central nervous system (CNS) acts to maintain balance after sudden perturbations of stance. Here, a sliding mode control (SMC) model for the characterization of balance maintenance after external perturbations is proposed. Human stance was modeled as an inverted pendulum (IP), which describes kinematics in the sagittal plane; the choice of a SMC allowed to avoid model linearization, commonly employed when using a single-link IP for bipedal stance modeling, thus providing a more accurate description of the human-stance system dynamics. Model was applied on experimental data obtained from perturbed stance trials consisting of a series of disruptions of the same magnitude. This experimental condition was able to elicit a well-known feature called “habituation rate”, which refers to the subject capacity to self-adapt his/her responses to identical perturbations. SMC parameters were identified through a robust optimization procedure. Results showed limited tracking errors for center of mass displacement. One of the SMC parameters exhibited a clear trend from the first to the last trial, appearing able to quantify the habituation rate effect. The application of such a control model to the non-quiet stance can provide additional information in understanding how the CNS tailors balance responses in different conditions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260810 Collegamento a IRIS

2018 Position estimation of an IMU placed on Pelvis through meta-heuristically optimised WFLC
IFMBE Proceedings
Autore/i: CARDARELLI, STEFANO; VERDINI, Federica; MENGARELLI, ALESSANDRO; STRAZZA, ANNACHIARA; DI NARDO, Francesco; BURATTINI, Laura; FIORETTI, Sandro
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260811 Collegamento a IRIS

2018 Antagonist activity of extensor digitorum brevis and tibialis anterior during child walking
MeMeA 2018 - 2018 IEEE International Symposium on Medical Measurements and Applications, Proceedings
Autore/i: STRAZZA, ANNACHIARA; Sara Palmieri, Michela; Orsini, Ornella; MENGARELLI, ALESSANDRO; BURATTINI, Laura; Bortone, Antonio; FIORETTI, Sandro; DI NARDO, Francesco
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Synergic and antagonist actions of intrinsic and extrinsic foot muscles are acknowledged during walking of adult people. Conversely, reciprocal role of these muscles in children walking has not been adequately deepened yet. Purpose of the study was the surface-EMG-based evaluation of mutual recruitment of intrinsic and extrinsic foot muscles during healthy-children walking. Extensor digitorum brevis (EDB) is one of the main intrinsic foot muscles, controlling foot movement and stability. In this study, EDB and tibialis anterior (TA) were considered as representative of intrinsic and extrinsic foot muscles, respectively. Surface-EMG signals during 4-minute walking trial were acquired in eight healthy school-age children (mean±SD: age 8.3±1.7 years; height 136±8 cm; mass 30.9±6.2 kg) to fulfill the goal of the study. Then, Statistical gait analysis, a recent methodology performing a statistical characterization of gait, was applied to process EMG data. Data from an exceptional number of strides were acquired and analyzed to consider the expected variability (mean±SD = 265±30 strides for each child, nearly 2500 in total). Results showed that: 1) the most frequent recruitment of EDB muscle occurred between 25% and 55% of gait cycle, i.e. in Flat foot contact and Push off phases; 2) the most frequent recruitment of TA occurred from 55% to following 10% of gait cycle, i.e. during Swing and Heel strike phases. This indicated that the most significant EDB activity overlapped the region of no activity (or infrequent activity) for TA and vice versa. In conclusion, present study suggests that TA and EDB muscles acted mainly as antagonist muscles for foot/ankle-joint movement during children walking. These findings highlighted the need of measuring the mutual activity of extrinsic vs. intrinsic foot muscles as tool for a deeper understanding of mechanisms regulating ankle-foot stability and as a possible marker of pathology of neuro-muscular system.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260824 Collegamento a IRIS

2018 Gait asymmetry in winters group I hemiplegic children: Role of tibialis anterior
IFMBE Proceedings
Autore/i: Di Nardo, F; Mengarelli, A; Strazza, A.; Malavolta, M; Verdini, F.; Cardarelli, S.; Burattini, L.; Nascimbeni, A.; Fioretti, S.
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Abstract: Hemiplegia is a neurological disorder that occurs quite often in children, affecting up to one child in one thousand. Typically, only one side of the body is affected by hemiplegia, while the other side is maintaining an apparently normal behavior. Purpose of present analysis was assessing gait asymmetry in group I (W1) hemiplegic children according to Winters classification, where W1 is characterized by presence of drop foot in swing in the hemiplegic side. Asymmetry was quantified by differences between hemiplegic and non-hemiplegic side in terms of foot-floor contact and electromyographic (EMG) activity. Surface EMG from tibialis anterior (TA) and foot-floor contact data were acquired in ten hemiplegic W1 children during walking to fulfill this aim. An exceptional number of strides was analyzed to consider the data variability, expected in W1 (mean ± SD = 287 ± 62 strides for each child, more than 3000 in total). Statistical gait analysis, a recent methodology performing a statistical characterization of gait, was applied to process EMG data. The research was undertaken in compliance with ethical principles of Helsinki Declaration and approved by institutional expert committee. Results showed that asymmetries were detected in basographic data: W1 children showed a significant decrease (p < 0.05) of strides with normal foot-floor contact (HFPS sequence: heel contact, flat-foot contact, push-off, swing) in hemiplegic side with respect to non-hemiplegic side. Also, TA recruitment presented asymmetries during walking, characterized by a curtailed, less frequent activity (p < 0.05) during terminal swing and a lack of activity at heel strike in hemiplegic side, with respect to non-hemiplegic side. In conclusion, present study suggested that walking in W1 children is characterized by asymmetries in both foot-floor contact patterns and TA recruitment.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260831 Collegamento a IRIS

2018 A time-frequency approach for the assessment of dynamic muscle co-contractions
IFMBE Proceedings
Autore/i: Strazza, A.; Verdini, F.; Mengarelli, A.; Cardarelli, S.; Burattini, L.; Fioretti, S.; Di Nardo, F.
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Abstract: Co-contraction is defined as the activity of agonist and antagonist muscles around a joint, enhancing stability and balance. The quantitative assessment of muscle co-contractions would be meaningful for deepening the comprehension of this physiological mechanism. Thus, the purpose of this work is to quantify muscle co-contraction using energy localization in time-frequency domain of sEMG signal during straight walking. To this purpose, sEMG from tibialis anterior (TA) and gastrocnemius lateralis (GL) and basographic signals were acquired in five healthy subjects during walking. Basographic signals were analyzed to quantify foot-floor contact. sEMG signals were processed using Wavelet Transform (WT) to identify muscular co-contractions, according to the following steps. Daubechies (order 4 with 6 levels of decomposition) was chosen as mother wavelet. A denoising algorithm based on Daubechies mother wavelet was applied for removing noise from raw signals. Denoised signals were decomposed into WT coefficients with different frequency content, and then recombined to achieve the co-scalogram function, a localized statistical assessment of cross-energy density between signals. The localization of regions with maximum cross-energy density provided the assessment of co-contractions in time-frequency domain. This methodology applied to TA and GL signals was able to detect GL/TA co-contractions during mid-stance (30–34% of GC) phase, matching with literature. Moreover, WT approach was able to provide also the frequency band of information content for muscle co-contractions: 65–164 Hz. In conclusion, this study proposed WT cross-energy density as a reliable estimation of muscle co-contraction in time-frequency domain.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260829 Collegamento a IRIS

2018 Automatic Identification and Classification of Fetal Heart-Rate Decelerations from Cardiotocographic Recordings
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Sbrollini, Agnese; Carnicelli, Amalia; Massacci, Alessandra; Tomaiuolo, Leonardo; Zara, Tommaso; Marcantoni, Ilaria; Burattini, Luca; Morettini, Micaela; Fioretti, Sandro; Burattini, Laura
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Cardiotocography (CTG) consists in the simultaneous recording of two distinct traces, the fetal heart rate (FHR; bpm) and the maternal uterine contractions (UCs; mmHg). CTG analysis consists in the evaluation of specific features of traces, among which fetal decelerations (DECs) are considered the 'center-stage' since possibly related to fetal distress. DECs are classified based on their duration and occurrence in relation to UCs as prolonged, early, late and variable; each class associates to a specific status of the fetus health. Typically, CTG traces are visually interpreted; however, computerized CTG analysis may overcome subjectivity in CTG interpretation. Thus, this study proposes a new automatic algorithm for computerized identification and classification of DECs. The algorithm was tested on the 552 CTG recordings constituting the 'CTU-CHB intra-partum CTG database' of Physionet. Of these, 470 (85.15%) were found suitable for automatic DECs identification and classification. Overall, 5888 DECs were identified, of which 3255 (55.28%) were classified while the other 2633 (44.72%) remained unclassified due to very strict preliminary classification criteria (now required for avoiding misclassifications). Among the classified DECs, 468 (14.38%) were classified as prolonged, 1498 (46.02%) as early, 32 (0.98%) as late, 1257 (38.62%) as variable. Thus, among the classified DECs, the most common are the early and the variable ones (overall 84.64%), the occurrence of which ranged from 0 to 14 DECs per recording. These findings are in agreement with what reported in literature. In conclusion, the proposed algorithm for automatic DECs identification and classification represents a useful tool for computerized CTG analysis.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/262590 Collegamento a IRIS

2018 Automatic T-Wave Alternans Identification in Indirect and Direct Fetal Electrocardiography
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Marcantoni, Ilaria; Sbrollini, Agnese; Burattini, Luca; Morettini, Micaela; Fioretti, Sandro; Burattini, Laura
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Fetal T-wave alternans (TWA) is a still littleknown marker for severe fetus-heart instabilities and may be related to some currently unjustified fetal deaths. Automatically detecting TWA on direct fetal electrocardiograms (DFECG) means possibility of providing fetuses the right treatment during delivery. Instead, automatically identifying TWA on indirect fetal electrocardiograms (IFECG) means possibility of providing fetuses the right treatment even during pregnancy, when taking actions for outcome improvement is still possible. Moreover, TWA identification from IFECG is noninvasive, and thus safe for both fetuses and mothers. The aim of this work was testing the heart-rate adaptive match filter (HRAMF) for automatic TWA identification in IFECG and comparing HRAMF performance in IFECG against DFECG. To this aim, simultaneously recorded DFECG and IFECG tracings from 5 healthy fetuses were used ('Abdominal and Direct Fetal Electrocardiogram Database' from Physionet). TWA measurements (frequency, mean amplitude, maximum amplitude, and amplitude standard deviation) in IFECG (1.09±0.04 Hz, 11±5 μV, 21±12 μV and 7±3 μV) were of the same order of magnitude of those in DFECG (1.07±0.02 Hz, 9±2 μV, 30±11 μV and 6±2 μV). Moreover, a direct correlation (ñ) was found between maximum TWA and fetal heart rate (IFECG: ρ=0.999; P=0.022; DEFEG: ρ=0.642; P=0.243). Thus, HRAMF was able to detect TWA from IFECG as well as from DFECG.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/262587 Collegamento a IRIS

2018 Surface EMG patterns for quantification of thigh muscle co-contraction in school-age children: Normative data during walking
GAIT & POSTURE
Autore/i: Di Nardo, Francesco; Strazza, Annachiara; Mengarelli, Alessandro; Ercolani, Serena; Morgoni, Nicole; Burattini, Laura; Agostini, Valentina; Knaflitz, Marco; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: Muscle co-contractions are particularly relevant in analyzing children pathologies. To interpret surface electromyography (sEMG) in pathological conditions, reliable normative data in non-pathological children are required for direct comparison. Aim of the study was the quantification of co-contraction activity between quadriceps femoris (QF) and hamstring muscles during walking in healthy children. To this aim, Statistical gait analysis was performed on sEMG signals from rectus femoris (RF), vastus medialis (VM), and lateral hamstrings (LH), in 16401 strides walked by 100 healthy school-age children. Co-contractions were assessed as overlapping period between activation intervals of considered muscles. Results showed full superimpositions of LH with both RF and VL activity from terminal swing, 80–100% of gait cycle, to successive loading response (0–15% of gait cycle), in around 90% of strides, as reported in adults. This indicates that children regularly use a cocontraction activity between QF and hamstring muscles in weight acceptance during walking, supporting the hypothesis of a regulatory role of co-contraction in providing knee joint stability. Concomitant activity of QF and hamstring muscles was detected also during push-off phase (30–50% of gait cycle), showing a large variability intra and inter subjects and a lower occurrence frequency (around 25% of strides). This could be intended for controlling rapid knee flexion and/or stabilizing pelvis during body progression. Present findings represent the first attempt to provide normative sEMG dataset on variability of QF and hamstring muscles co-contractions during child walking, useful for discriminating physiological and pathological behavior and for designing future studies on maturation of gait.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/252424 Collegamento a IRIS

2018 Are extensor digitorum brevis and gastrocnemius working together? Surface EMG analysis in healthy children
IFMBE Proceedings
Autore/i: Di Nardo, F; Strazza, A; Palmieri, MS; Mengarelli, A; Cardarelli, S; Burattini, L; Orsini, O; Verdini, F; Bortone, A; Fioretti, S.
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Abstract: A relationship between intrinsic and extrinsic foot muscles is acknowledged during walking. Literature on foot-muscle recruitment in children is not very extensive. Purpose of the study was the surface-EMG-based evaluation of possible concomitant recruitment of intrinsic and extrinsic foot muscles during healthy-children walking. Gastrocnemius lateralis (GL) was analyzed as representative for extrinsic foot muscles (ankle plantar flexor). Extensor digitorum brevis (EDB) is one of the main intrinsic foot muscles, controlling foot movement and stability. In this study, EDB was considered as representative of foot muscles. Surface-EMG signals during 4-min walking trial were acquired in eight healthy school-age children (mean ± SD: age 8.3 ± 1.7 years; height 136 ± 8 cm; mass 30.9 ± 6.2 kg) to fulfill the goal of the study. Then, Statistical gait analysis, a recent methodology performing a statistical characterization of gait, was applied to process EMG data. An exceptional number of strides were analyzed to consider the expected variability (mean ± SD = 265 ± 30 strides for each child, nearly 2500 in total). The research was undertaken in compliance with ethical principles of Helsinki Declaration and approved by institutional expert committee. Results showed that EDB activity is localized in two separate regions of gait cycle: mid-stance (from 8.2 ± 7.0 to 50.3 ± 15.0% of gait cycle) and swing phase, from 73.8 ± 13.8 to 95.1 ± 4.7%. Main GL activity occurred in the same regions: mid-stance (from 5.7 ± 2.5 to 49.7 ± 4.6% of gait cycle) and swing phase, from 69.2 ± 18.7 to 95.4 ± 5.4%. These findings showed that regions of activity of EDB and GL were practically overlapped, suggesting that EDB and GL worked synergistically for foot and ankle-joint control in children walking, in a large percentage of strides. Present study produced novel data on the variability of the reciprocal role of EDB and GL during children walking, providing a deeper insight in mechanisms regulating ankle-foot stability.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260833 Collegamento a IRIS

2018 Co-activation patterns of gastrocnemius and quadriceps femoris in controlling the knee joint during walking
JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY
Autore/i: Mengarelli, Alessandro; GENTILI, ANDREA; Strazza, Annachiara; Burattini, Laura; Fioretti, Sandro; Di Nardo, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: Muscular co-activation is a well-known mechanism for lower limb joint stabilization in both healthy and pathological individuals. This muscular feature appears particularly important for the knee joint, not only during challenging motor tasks such as cutting and landing but also during walking, due to knee cyclic loading. Gastrocnemius acts on the knee joint with a flexor activity and co-activations with quadriceps muscles lead to greater knee ligament strain with respect to an isolated burst of either muscle. Thus, this study aimed to assess possible co-activations between gastrocnemius and quadriceps muscles during walking. Five co-activation periods were assessed: during early stance (identified in 5.7 ± 5.1% of total strides), early and late foot-contact (88.9 ± 8.9% and 8.9 ± 8.2%), push-off (23.9 ± 12.2%) and late swing (29.0 ± 16.1%). Outcomes showed that late foot-contact and swing co-activations could deserve particular attention: in both cases the knee joint was close to the full extension (around 3.5° and 6° respectively) and thus, considering also the anterior tibia translation due to the quadriceps activity, the simultaneous gastrocnemius burst could lead to an enhanced knee ligaments elongation. Findings of this study represent the first attempt to provide a reference knee joint co-activation framework, useful also for further evaluation in cohorts with knee failures.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260181 Collegamento a IRIS

2018 Electrocardiogram Derived Respiratory Signal through the Segmented-Beat Modulation Method
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Pambianco, Benedetta; Sbrollini, Agnese; Marcantoni, Ilaria; Morettini, Micaela; Fioretti, Sandro; Burattini, Laura
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Respiration rate and variability are indicators of health-condition changes. In chronic disease management, it is becoming increasingly desirable to use wearable devices in order to minimize invasiveness and maximize comfort. However, not all wearable devices integrate sensors for direct acquisition of respiratory (DAR) signal. In these cases, the breathing extraction can be done through indirect methods, typically from the electrocardiogram (ECG). The aim of the present study is to propose a single-ECG-lead procedure based on the Segmented-Beat Modulation Method (SBMM) as a suitable tool for ECG-derived respiratory (EDR) signal estimation and respiration frequency (RF) identification. Clinical data consisted of combined measurements of two-lead (I and II) ECG and DAR signals from 20 healthy subjects ('CEBS' database by Physionet). Each respiration-affected ECG lead was submitted to a specifically designed SBMMbased procedure for EDR estimation by ECG subtraction. RF from EDR and DAR were identified as the frequency at which the Fourier spectrum has a maximum in the 0.07-1.00 Hz frequency range. Results indicated that mean RF values over the population from EDR signals (0.27 ± 0.09 Hz and 0.27 ± 0.09 Hz from leads I and II, respectively) were not significantly different from that from DAR (0.28 ± 0.09 Hz). Moreover, differences in RF identification (0.01 ± 0.03 Hz and 0.00 ± 0.02 Hz from leads I and II, respectively) were, on average not significantly different from 0. Thus, SBMM-based procedure is robust and accurate for EDR estimation and RF identification.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/262588 Collegamento a IRIS

2018 PCG-Delineator: an Efficient Algorithm for Automatic Heart Sounds Detection in Fetal Phonocardiography
Computing in Cardiology
Autore/i: Strazza, Annachiara; Sbrollini, Agnese; di Battista, Valeria; RICCI, RITA; TRILLINI, LETIZIA; Marcantoni, Ilaria; Morettini, Micaela; Fioretti, Sandro; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Fetal phonocardiography (FPCG) is a non-invasive electronic recording of the acoustic cardiac signals. Unfortunately, FPCG is hidden by high-amplitude noise which makes detection of FPCG waveforms challenging. Aim of the study is to propose PCG-Delineator as an algorithm for automatic detection of the first and second heart sound (S1 and S2, respectively) from FPCG. To this aim, 37 simulated FPCG tracings (Physionet) are filtered by a wavelet-based procedure (4th order Coiflets mother wavelet with 7 decomposition levels) to erase noise. Successively, S1 and S2 are detected. S1 detection procedure is threshold-based (threshold=30% of the filtered FPCG signal maximum amplitude), under the condition that 40ms separate two consecutive S1 sounds. S2 detection procedure is also threshold-based, but under the conditions that S2 has to fall 100ms after preceding S1 and 200ms before successive S1, and that S2 has to have an amplitude lower than 80% that of preceding S1. Sensitivity (SE) and positive predictive values (PPV) were computed. Results indicate that PCG-Delineator was able to reduce noise (our SNR: from -1.1÷7.4dB to 12.9÷17.9dB; P<10-14) and to accurately detect both S1 (SE: 88%; PPV: 91%) and S2 (SE: 77%; PPV:99%). In conclusion, PCG-Delineator is an efficient algorithm for automatic heart sounds detection in FPCG.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/264730 Collegamento a IRIS

2018 Detection of surface-EMG activity from the extensor digitorum brevis muscle in healthy children walking
PHYSIOLOGICAL MEASUREMENT
Autore/i: Di Nardo, Francesco; Strazza, Annachiara; Palmieri, Michela Sara; Mengarelli, Alessandro; Burattini, Laura; Orsini, Ornella; Bortone, Antonio; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: Objective: The purpose of the study was the assessment of activation patterns of the extensor digitorum brevis (EDB) muscle in healthy children, during walking at self-selected speed and cadence. Approach: To this end, statistical gait analysis was performed on surface electromyographic (sEMG) signals of the EDB, in a large number (hundreds) of strides per subject. sEMG data from the tibialis anterior (TA) and gastrocnemius lateralis (GL) were also investigated for comparative purposes. Main results: Results from 23 healthy children showed a large variability in the number of muscle activations, occurrence frequency, and onset-offset instants across considered strides. The assessment of different modalities of muscle activation allowed the identification of a single activity pattern, common to all the modalities and we were able to characterize the behavior of the EDB during the gait of healthy children. The pattern of EDB activity centered in two main regions of the gait cycle: in the second half of the stance phase (detected in 100% of subjects) and in the final swing phase (50%). Comparison with the TA and GL regions of activity suggested that the EDB and TA worked mainly as antagonist muscles for the ankle joint, while the EDB and GL did not oppose each other in action, but acted in synergy for the control of the ankle joint during walking. Significance: The 'Normality' pattern for the EDB activity reported here represents the first attempt to develop a reference for dynamic sEMG of the EDB in healthy children, enabling us to include the physiological variability of the phenomenon. Present results could be useful for discriminating physiological and pathological behavior in children and for deepening the maturation of the gait.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/253158 Collegamento a IRIS

2018 Ankle muscles co-activation during walking: A gender comparison in adults and children
2017 IEEE Biomedical Circuits and Systems Conference, BioCAS 2017 - Proceedings
Autore/i: MENGARELLI, ALESSANDRO; STRAZZA, ANNACHIARA; FIORETTI, Sandro; BURATTINI, Laura; DI NARDO, Francesco; Agostini, Valentina; Knaflitz, Marco
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The present study aimed to evaluate possible gender-related differences in adults and children co-activation and antagonistic behavior of ankle muscles (Tibialis Anterior and Gastrocnemius) during walking. The statistical gait analysis technique, applied to a total of 40 subjects (20 children and 20 young adults), allowed the statistical description of gait, considering spatial-temporal and electromyography parameters over a large number (hundreds) of consecutive strides per subject. Co-activations were computed as the overlapping periods of muscles bursts, while antagonism occurred when no simultaneous muscular activity was detected. Outcomes showed no significant differences in temporal characteristics of co-activations in children and adults. Evaluating antagonistic and co-contraction activity in terms of number of strides where each pattern happened, i.e. their occurrence frequency, no significant differences were observed between males and females in children, while in adults group co-contraction pattern resulted significantly more recurrent in females with respect to males. Furthermore, the direct comparison between adults and children showed significant differences in the recurrence of both co-activation and antagonist pattern only for males. Results suggested a possible age-related change in males muscular recruitment during walking, which could lead to the gender differences in co-contraction activity observed in adults but not in children.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260804 Collegamento a IRIS

2018 Assessment of glucose effectiveness from short IVGTT in individuals with different degrees of glucose tolerance
ACTA DIABETOLOGICA
Autore/i: MORETTINI, Micaela;   ·, Francesco  Di  Nardo; BURATTINI, Laura; FIORETTI, Sandro; Christian  Göbl,   ·; Alexandra  Kautzky‑Willer,   ·; Giovanni  Pacini,   ·; Andrea  Tura,   ·
Classificazione: 1 Contributo su Rivista
Abstract: Aims Minimal model analysis of intravenous glucose tolerance test (IVGTT) data represents the reference method to assess insulin sensitivity (SI) and glucose effectiveness (SG) that quantify the insulin-dependent and insulin-independent processes of glucose disappearance, respectively. However, test duration (3 h) and need for modeling expertise limit the applicability of this method. Aim of this study was providing a simple predictor of SG applicable to short test (1 h), as previously done with SI. Methods Three groups of subjects reflecting different glucose tolerance degrees underwent a 3 h IVGTT: subjects with normal glucose tolerance (NGT, n = 164), with defective glucose regulation (DGR, n = 191), and with type 2 diabetes (T2D, n = 39). Minimal model analysis provided reference SG and its components at zero (GEZI) and basal (BIE) insulin. The simple predictor CSG (calculated SG) was described by the formula CSG = α0 + α1 × KG/Gpeak, being KG the glucose disappearance rate (between 10 and 50 min) and Gpeak the maximum of the glucose curve during the test; α0 and α1 coefficients were provided by linear regression analysis. Results CSG and SG showed a markedly significant relationship in the whole dataset (r = 0.72, p < 0.0001) and in the single groups (r = 0.70 in NGT, r = 0.71 in DGR and r = 0.70 in T2D, p < 0.0001 for all); α1 × KG/Gpeak was significantly related to GEZI (r ≥ 0.60). Conclusions The interest for insulin-independent glucose disappearance is increasing, due to the recent availability of SGLT2 pharmacological agents, lowering glycemic levels without requiring insulin action. This study proposes a reliable predictor of SG based on IVGTT lasting 1 h only, and not requiring mathematical modeling skills.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260624 Collegamento a IRIS

2018 eCTG: an automatic procedure to extract digital cardiotocographic signals from digital images
COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE
Autore/i: Sbrollini, Agnese; Agostinelli, Angela; MARCANTONI, ILARIA; Morettini, Micaela; Burattini, Luca; Di Nardo, Francesco; Fioretti, Sandro; Burattini, Laura
Classificazione: 1 Contributo su Rivista
Abstract: Background and objective: Cardiotocography (CTG), consisting in the simultaneous recording of fetal heart rate (FHR) and maternal uterine contractions (UC), is a popular clinical test to assess fetal health status. Typically, CTG machines provide paper reports that are visually interpreted by clinicians. Consequently, visual CTG interpretation depends on clinician's experience and has a poor reproducibility. The lack of databases containing digital CTG signals has limited number and importance of retrospective studies finalized to set up procedures for automatic CTG analysis that could contrast visual CTG interpretation subjectivity. In order to help overcoming this problem, this study proposes an electronic procedure, termed eCTG, to extract digital CTG signals from digital CTG images, possibly obtainable by scanning paper CTG reports. Methods: eCTG was specifically designed to extract digital CTG signals from digital CTG images. It includes four main steps: pre-processing, Otsu's global thresholding, signal extraction and signal calibration. Its validation was performed by means of the “CTU-UHB Intrapartum Cardiotocography Database” by Physionet, that contains digital signals of 552 CTG recordings. Using MATLAB, each signal was plotted and saved as a digital image that was then submitted to eCTG. Digital CTG signals extracted by eCTG were eventually compared to corresponding signals directly available in the database. Comparison occurred in terms of signal similarity (evaluated by the correlation coefficient ρ and the mean signal error MSE) and clinical features (including FHR baseline and variability; number, amplitude and duration of tachycardia, bradycardia, acceleration and deceleration episodes; number of early, variable, late and prolonged decelerations; and UC number, amplitude, duration and period). Results: The value of ρ between eCTG and reference signals was 0.85 (P < 10−560) for FHR and 0.97 (P < 10−560) for UC. On average, MSE value was 0.00 for both FHR and UC. No CTG feature was found significantly different when measured in eCTG vs. reference signals. Conclusions: eCTG procedure is a promising useful tool to accurately extract digital FHR and UC signals from digital CTG images.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/255236 Collegamento a IRIS

2018 Balance assessment during squatting exercise: A comparison between laboratory grade force plate and a commercial, low-cost device
JOURNAL OF BIOMECHANICS
Autore/i: Mengarelli, Alessandro; Verdini, Federica; Cardarelli, Stefano; Di Nardo, Francesco; Burattini, Laura; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: Testing balance through squatting exercise is a central part of many rehabilitation programs and sports and plays also an important role in clinical evaluation of residual motor ability. The assessment of center of pressure (CoP) displacement and its parametrization is commonly used to describe and analyze squat movement and the laboratory-grade force plates (FP) are the gold standard for measuring balance performances from a dynamic view-point. However, the Nintendo Wii Balance Board (NWBB) has been recently proposed as an inexpensive and easily available device for measuring ground reaction force and CoP displacement in standing balance tasks. Thus, this study aimed to compare the NWBB-CoP data with those obtained from a laboratory FP during a dynamic motor task, such as the squat task. CoP data of forty-eight subjects were acquired simultaneously from a NWBB and a FP and the analyses were performed over the descending squatting phase. Outcomes showed a very high correlation (r) and limited root-mean-square differences between CoP trajectories in anterior-posterior (r > 0.99, 1.63 ± 1.27 mm) and medial-lateral (r > 0.98, 1.01 ± 0.75 mm) direction. Spatial parameters computed from CoP displacement and ground reaction force peak presented fixed biases between NWBB and FP. Errors showed a high consistency (standard deviation < 2.4% of the FP outcomes) and a random spread distribution around the mean difference. Mean velocity is the only parameter which exhibited a tendency towards proportional values. Findings of this study suggested the NWBB as a valid device for the assessment and parametrization of CoP displacement during squatting movement.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/256928 Collegamento a IRIS

2018 Validity of the Nintendo Wii Balance Board for the Assessment of Balance Measures in the Functional Reach Test
IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING
Autore/i: Mengarelli, Alessandro; Cardarelli, Stefano; Strazza, Annachiara; Di Nardo, Francesco; Fioretti, Sandro; Verdini, Federica
Classificazione: 1 Contributo su Rivista
Abstract: The functional reach test (FRT) is widely used for assessing dynamic balance stability in elderly and pathological subjects. Force platforms (FPs) represent a fundamental part of the instrumented FRT experimental setup due to the central role of center-of-pressure (COP) displacement in FRT analysis. Recently, the nintendo wii balance board (NBB) has been suggested as a low-cost and reliable device for ground reaction force and COP measurement in poorly dynamic motor tasks. Therefore, this paper aimed to compare NBB-COP data with those obtained from a laboratory-grade platform during FRT. Data from 48 healthy subjects were simultaneously acquired from both devices. FP-COP and NBB-COP trajectories showed a remarkable correlation in both directions (r>0.990) and low root-mean-square error values (1.14 ± 0.88 mm and 0.55 ± 0.28 mm for anterior-posterior and medial-lateral direction). Fixed biases between COP-based parameters did not exceed 2% of the FP outcomes with high consistency throughout the present measurement range (ICC consistency always >0.950). Only the COP mean velocity exhibited a tendency toward proportional errors, which can be adjusted by a calibration of NBB data. Findings of this paper confirmed the NBB validity for COP measurement in a widely used motor task as the functional reach, supporting the feasibility of NBB in research scenarios.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/259193 Collegamento a IRIS

2017 Simple assessment of insulin sensitivity in the zucker rat
IFMBE Proceedings
Autore/i: MORETTINI, MICAELA; Faelli, E.; Perasso, L.; FIORETTI, Sandro; BURATTINI, LAURA; Ruggeri, P.; DI NARDO, Francesco
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The model-based assessment of insulin sensitivity in Zucker rat from Intravenous Glucose Tolerance Test (IVGTT) data is a common procedure. The minimal model methodology provides a very reliable assessment but requires specific competence for running the model. The aim of this study was presenting calculated SI (CSI), as a surrogate index for the simple assessment of insulin sensitivity in the Zucker Rat from IVGTT data. To this aim 25 Zucker Lean Rats (ZLR) and 25 Zucker Fatty Rats (ZFR) were considered. Reference insulin sensitivity (SI) was estimated in each rat through the minimal model methodology. CSI is defined as the ratio between the rate of glucose disappearance (KG) and the mean supra-basal area under the insulin curve during the test (ΔAUCINS), corrected by the proportionality term, α. Regression analysis between SI and KG/ΔAUCINS was performed to identify the α coefficient. Results showed as the computed value of CSI presented a high correlation (r = 0.89, R-square = 0.80 and p < 0.0001, slope ≈1) with SI. Mean value of CSI over the whole population was not significantly different from correspondent SI value (p = 0.17). CSI is able to detect the well-known reduction of insulin sensitivity in the ZFR group (1.0±0.1 vs. 5.0±0.7 min-1/μU·ml-1, p < 0.001), in accordance with the results provided by SI. In conclusion, the present study proposes CSI, as a suitable empiric index for a simple and reliable assessment of insulin sensitivity in Zucker rat and able to provide the same quantitative information of model-based SI.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/250217 Collegamento a IRIS

2017 No changes in glucose effectiveness in condition of reduced insulin action but preserved glucose tolerance as assessed by minimal model analysis
IFMBE Proceedings
Autore/i: MORETTINI, MICAELA; DI NARDO, Francesco; FIORETTI, Sandro; Pacini, G.; Tura, A.; BURATTINI, LAURA
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Glucose effectiveness (SG) represents the ability of glucose per se, under basal insulin concentrations, to stimulate its own uptake and to suppress its own production. SG and its two components BIE (Basal Insulin Effect) and GEZI (Glucose Effectiveness at Zero Insulin) are known to decline in subjects whose glycemic status worsens, but no study aimed to analyze whether changes may occur even before, when a normal glucose tolerance status is still preserved but insulin resistance has already arisen. To investigate this issue, SG, BIE and GEZI were estimated from the minimal model interpretation of frequently sampled intravenous glucose tolerance (FSIGT) test data in two groups of subjects with normal glucose tolerance (basal glycemia < 5.6 mmol/l): a group of control participants (CNT, n=50) and a group of subjects with pathologies or conditions causing insulin resistance (IR, n=50). No difference in mean values of SG was observed in the IR with respect to the CNT group (2.3 ± 0.9 vs. 2.5 ± 0.9 10-2 min-1; p = 0.17). BIE was found to be the minor component of SG in both CNT and IR group. The GEZI component provided a significantly higher proportional contribution to SG in the IR with respect to CNT (89% vs. 81% of SG, p <0.0001). In proportion, a significantly lower contribution was provided by BIE in IR group (11 ± 1 vs. 18 ± 1, p <0.0001). These results indicate that, at the real starting phase of the process of glucose tolerance impairment (reduced insulin action but normal tolerance), no variation in SG occurs with respect to normality. An increased proportional contribution of GEZI, when BIE declines, may allow the maintenance of normal glucose effectiveness.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/250219 Collegamento a IRIS

2017 Center of pressure based assessment of balance responses to repeated perturbations of upright stance
IFMBE Proceedings
Autore/i: MENGARELLI, ALESSANDRO; CARDARELLI, STEFANO; FIORETTI, Sandro; BURATTINI, LAURA; DI NARDO, Francesco; VERDINI, Federica
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In this study a description of balance response to sudden external perturbations of the upright posture was performed. To this aim, subjects underwent to a series of translational perturbations at fixed speed in backward and forward direction. Center of pressure (CoP) displacement was analyzed in terms of temporal and spatial characteristics, showing a repeatable waveform which allowed the identification of two main response periods: the destabilizing and the counterbalancing phase. Different control features of balance response have been observed in both phases, with a temporal-based control of CoP displacement in the first phase and an amplitude-based control in the second one. Moreover, the analysis of CoP could be useful to identify the presence of the first trial effect and the habituation rate, two well-known features of perturbed posturography. These findings could contribute to the understanding of balance control in perturbed conditions and suggest CoP as a valuable measure in studying not only the quiet but also the perturbed stance.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/250214 Collegamento a IRIS

2017 Epidemiology/Genetics
DIABETES
Autore/i: Morettini, Micaela; DI NARDO, Francesco; Burattini, Laura; Fioretti, Sandro; Tura, Andrea; Pacini, Giovanni
Classificazione: 1 Contributo su Rivista
Abstract: Two are the main processes regulating post-challenge glucose uptake: one insulin-dependent, and the other mainly due to glucose disappearance per se (glucose effectiveness, SG, min-1), accounting for 60-80% of the whole disappearance. Aim of this study was providing an easy method for assessing SG with a short IVGTT (regular). Three groups of subjects were considered: CNT (control subjects, with normal glucose tolerance: n=158), PRE (subjects with prediabetes and/or pathologies causing insulin resistance: n=220), and T2D (subjects with type 2 diabetes: n=31). Fasting glucose and insulin (mean±SD) were 4.7±0.6, 4.8±0.9, 5.9±1.0 mmol·L-1 and 8.3±3.8, 12.3±9.3, 11.0±4.3 pmol·L-1, for CNT, PRE, T2D, respectively. Reference SG was assessed by Minimal Model analysis. In all grouped subjects, regression analyses were performed to identify a simple predictor (calculated SG, CSG) of reference SG, yielding CSG=α0+α1·KG/Gpeak, with KG slope of the glucose curve (10-50 min), Gpeak maximum glucose, α0=0.007 and α1=0.141. We found SG=0.022±0.010 min-1 and CSG=0.021±0.007 min-1. CSG showed excellent correlation with SG (r=0.65, p<0.001). Similar results were found in each group (r=0.64, p<0.001 in CNT, r=0.63, p<0.001 in PRE, r=0.75, p<0.001 in T2D). Also, SG and CSG were not significantly different, both in all subjects (p=0.34, paired t-test) and in the single groups (p>0.10). Bland-Altman analysis confirmed the substantial equivalence of the two indices, showing only 5% of samples outside the limits of agreement (both in all subjects and the single groups). When comparing SG and CSG among groups, both indices consistently showed lower values in PRE and T2D compared to CNT (p<0.008 for SG and p<0.0001 for CSG, by ANOVA). In conclusion, the first 50 minutes of the IVGTT are sufficient to yield a reliable estimation of glucose effectiveness through a simple approach, not requiring sophisticated mathematical modeling.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/255420 Collegamento a IRIS

2017 Statistical baseline assessment in cardiotocography
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Agostinelli, Angela; Braccili, Eleonora; Marchegiani, Enrico; Rosati, Riccardo; Sbrollini, Agnese; Burattini, Luca; Morettini, Micaela; Di Nardo, Francesco; Fioretti, Sandro; Burattini, Laura
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Cardiotocography (CTG) is the most common non-invasive diagnostic technique to evaluate fetal well-being. It consists in the recording of fetal heart rate (FHR; bpm) and maternal uterine contractions. Among the main parameters characterizing FHR, baseline (BL) is fundamental to determine fetal hypoxia and distress. In computerized applications, BL is typically computed as mean FHR±ΔFHR, with ΔFHR=8 bpm or ΔFHR=10 bpm, both values being experimentally fixed. In this context, the present work aims: to propose a statistical procedure for ΔFHR assessment; to quantitatively determine ΔFHR value by applying such procedure to clinical data; and to compare the statistically-determined ΔFHR value against the experimentally-determined ΔFHR values. To these aims, the 552 recordings of the 'CTU-UHB intrapartum CTG database' from Physionet were submitted to an automatic procedure, which consisted in a FHR preprocessing phase and a statistical BL assessment. During preprocessing, FHR time series were divided into 20-min sliding windows, in which missing data were removed by linear interpolation. Only windows with a correction rate lower than 10% were further processed for BL assessment, according to which ΔFHR was computed as FHR standard deviation. Total number of accepted windows was 1192 (38.5%) over 383 recordings (69.4%) with at least an accepted window. Statistically-determined ΔFHR value was 9.7 bpm. Such value was statistically different from 8 bpm (P<10-19) but not from 10 bpm (P=0.16). Thus, ΔFHR=10 bpm is preferable over 8 bpm because both experimentally and statistically validated.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/255427 Collegamento a IRIS

2017 Antagonist thigh-muscle activity in 6-to-8-year-old children assessed by surface EMG during walking
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Di Nardo, Francesco; Strazza, Annachiara; Mengarelli, Alessandro; Ercolani, Serena; Burattini, Laura; Fioretti, Sandro
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Analysis of muscle co-contractions seems to be relevant in the characterization of children pathologies such as spastic cerebral palsy. The aim of the study was the quantification of thigh-muscle co-contractions during walking in healthy children. To this aim, the Statistical Gait Analysis, a recent methodology providing a statistical characterization of gait, was performed on surface EMG signals from Vastus Medialis (VM) and Lateral Hamstrings (LH) in 30 healthy 6-to-8-year-old children. Muscular co-contraction was assessed as the overlapping period between activation intervals of agonist and antagonist muscles. As in adults, VM activity occurring from terminal swing to the following loading response superimposed LH activity in the same percentage of the gait cycle. This co-contraction occurred in order to control knee joint stability during weight acceptance. It was acknowledged in the totality (100 %) of the considered strides. Concomitant activity of VM and LH was detected also in the second half of stance phase in 17.1 ± 4.8 % of the considered strides. Working VM and LH on different joints, this concomitant activity of antagonist muscles should not be considered as an actual co-contraction. Present findings provide new information on the variability of the reciprocal role of VM and LH during child walking, useful for comparison between normal and pathological walking in the clinical context and for designing future studies on maturation of gait.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/255429 Collegamento a IRIS

2017 Overnight T-wave alternans in sleep apnea patients
Computing in Cardiology
Autore/i: Burattini, Laura; Ciotti, Ilaria; D'Ignazio, Michela; Miccoli, Alessandro; Agostinelli, Angela; Sbrollini, Agnese; Morettini, Micaela; Di Nardo, Francesco; Fioretti, Sandro
Editore: IEEE Computer Society
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Sleep apnea (SA) is linked to cardiovascular complications and to an increased risk of sudden cardiac death. Microvolt T-wave alternans (TWA) is a noninvasive electrocardiographic (ECG) index of cardiovascular risk; its rate of occurrence in SA patients remains unknown. Thus, this study investigated the occurrence of TWA in SA patients during night. To this aim, overnight ECG recordings of 16 SA patients were analyzed for TWA identification by means of our heart rate adaptive match filter. Results indicate that overnight TWA was characterized by a low mean amplitude (mean TWA: 6±3 µV). However, higher-amplitude transient TWA episodes (max TWA: 29±21 µV) occurred overnight, sometimes when patients were awake (max TWA: 33±18 µV; 56% of cases) and sometimes when patients were sleeping (max TWA: 24±23 µV; 44% of cases with 13%, 19%, 6% and 6% during sleep stage 1, 2, 3 and 4, respectively). In only 3 subjects (19%) TWA peaks occurred during an SA episode: during obstructive apnea with arousal in two cases (max TWA of 7 µV and 17 µV, during stages 1 and 2, respectively) and during hypoapnea with arousal in one case (max TWA of 6 µV while awake). Thus, SA patients show significant transient overnight TWA episodes, not necessarily occurring during a SA episode.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/259391 Collegamento a IRIS

2017 Second heart sound onset to identify T-wave offset
Computing in Cardiology
Autore/i: Sbrollini, Agnese; Bartoli, Marta Beghella; Agostinelli, Angela; Morettini, Micaela; Di Nardo, Francesco; Fioretti, Sandro; Burattini, Laura
Editore: IEEE Computer Society
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Phonocardiography (PCG) second heart sound represents aortic-pulmonary valves closure and beginning of isovolumetric relaxation of the ventricles. Electrocardiography (ECG) T wave represents electrical repolarization of the ventricles. Ventricular electrical repolarization is known to drive ventricular mechanical relaxation. Thus, the aim of the present study was to investigate whether, in normal conditions, second heart sound onset (S2on) matches in time T-wave offset (Toff) so that S2on may be used to identify Toff. To this aim, 99 couples of simultaneously recorded short (around 30 s PCG and ECG) signals relative to normal subjects (selected from PhysioNet/CinC Challenge 2016: Training Set A) were analyzed. S2on was identified by application of our newly developed threshold-based algorithm to the median beat of the PCG envelope. Instead, Toff was identified by application of the Laguna and Thakor algorithm to the median ECG beat. Median time-distance (δt) between S2on and Toff was 5 ms (P=0.007). Thus, in normal conditions, S2on and Toff differ on average of 5 ms, whose meaning remain to be defined. Still, 5 ms is included in the Toff identification variability (of the order of tens ms) due to different Toff identification methods and electrocardiographic leads. Consequently, in normal condition, S2on may be used to estimate Toff
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/259389 Collegamento a IRIS

2017 T-Wave alternans identification in direct fetal electrocardiography
Computing in Cardiology
Autore/i: Marcantoni, Ilaria; Vagni, Marica; Agostinelli, Angela; Sbrollini, Agnese; Morettini, Micaela; Burattini, Luca; Di Nardo, Francesco; Fioretti, Sandro; Burattini, Laura
Editore: IEEE Computer Society
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Very little is known about the incidence and etiology of fetal T-wave alternans (TWA), an electrophysiologic phenomenon potentially associated to fetal suboptimal outcomes. Thus, availability of automatic methods for quantification of TWA from digital electrocardiograms (ECG) is desirable, since TWA occurrence might indicate the need of taking actions before or during delivery. The heart-rate adaptive match filter (HRAMF) is a wellestablished method to identify TWA in adult ECG. Aim of the present study was to investigate the possibility of using HRAMF to identify and quantify TWA also in direct fetal ECG (DFECG) recordings. To this aim, HRAMF was applied to 5 min-long DFECG acquired during delivery (“Abdominal and Direct Fetal Electrocardiogram Database” by Physionet) of five healthy fetuses. Significant levels of TWA were measured in all DFECG. Specifically, on average, TWA was quite high in amplitude (9±2 µV) and variable in time, as indicated by values of standard deviation (6±2 µV) and maximum (28±10 µV) of TWA amplitude. Eventually, a positive correlation (ρ=0.68) was observed between maximum TWA and fetal heart rate, even though the limited number of recordings makes this result preliminary. In conclusion, HRAMF proved to be a suitable tool to automatically identify TWA from DFECG.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/259390 Collegamento a IRIS

2017 Quantification of fetal ST-segment deviations
Computing in Cardiology
Autore/i: Agostinelli, Angela; Di Cosmo, Mariachiara; Sbrollini, Agnese; Burettini, Luca; Morettini, Micaela; Di Nardo, Francesco; Fioretti, Sandro; Burattini, Laura
Editore: IEEE Computer Society
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: By fetal electrocardiogram (FECG) analysis it has been found that changes in the ST segment are associated with acid-base status, and thus fetus health state. Currently, the most popular estimation of fetal STsegment deviations is performed as ratio between T-wave height and QRS-complex amplitude using the STAN monitor. Thus, this evaluation is indirect because not directly derived from measurements on the ST segment. This study proposes a new procedure for an automated direct quantification of fetal ST-segment deviations, which are described in terms of ST-amplitude and STtrend. Particularly, ST-amplitude corresponds to the maximum of the mean amplitude values obtained through a moving-average (15 ms) operation over the ST segment. Instead, ST-trend corresponds to the difference between the ST-segment amplitudes calculated in the first and the last of three intervals in which the ST segment is divided; thus, ST-trend sign indicates a ST-segment elevation (positive sign) or depression (negative sign). The procedure was evaluated on five direct FECG recordings (in https://physionet.org/physiobank/database/adfecgdb/). Mean values (over population) of ST-amplitude and STtrend were 9.6 ± 5.5 μV and 1.4 ± 2.3 μV, respectively. All found values were validated by visual inspection of the magnified FECG plots.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/259395 Collegamento a IRIS

2017 Fetal phonocardiogram denoising by wavelet transformation: Robustness to noise
Computing in Cardiology
Autore/i: Sbrollini, Agnese; Strazza, Annachiara; Caragiuli, Manila; Mozzoni, Claudia; Tomassini, Selene; Agostinelli, Angela; Morettini, Micaela; Fioretti, Sandro; Di Nardo, Francesco; Burattini, Laura
Editore: IEEE Computer Society
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Fetal phonocardiography (fPCG) is a clinical test to assess fetal wellbeing during pregnancy, labor and delivery. Still, its interpretation may be jeopardized by the presence of noise. Specifically, fPCG is typically corrupted by maternal heart and body organs sounds, fetal movements noise and surrounding environment noise. Thus, appropriate filtering procedures have to be applied in order to make fPCG clinically usable. Wavelet transformation (WT) has been proposed to filter fPCG; however, WT robustness to noise remains unknown. Thus, aim of the present work is to evaluate WT ability and robustness to denoise fPCG characterized by varying signal-to-noise ratios (SNR). To this aim a filtering procedure based on Coiflets mother wavelet (4th order, 7 levels of decomposition) was applied to 37 fPCG simulated tracings, all available in the Simulated Fetal PCGs database by Physionet. Original SNR values ranged from -1.38 dB to 4.54 dB; after application of WT-filtering procedure to fPCG, SNR increased significantly, ranging from 12.95 dB to 17.94 dB (P<10- 14). Moreover, SNR values before and after filtering were associated by a low correlation (ρ=0.4; P=0.01). Eventually, WT filtering introduced no fPCG signal delay and left heart rate unaltered. Thus, WT filtering is a suitable and robust technique to denoise fPCG signals.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/259394 Collegamento a IRIS

2017 Association between accelerations and decelerations of fetal heart rate
IFMBE Proceedings
Autore/i: AGOSTINELLI, ANGELA; Belgiovine, G.; Fiorentino, M. C.; Turri, G.; SBROLLINI, AGNESE; BURATTINI, LAURA; MORETTINI, MICAELA; DI NARDO, Francesco; FIORETTI, Sandro; BURATTINI, LAURA
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Cardiotocography (CTG) is the most popular test for establishing the fetal health status. Among its characterizing features there are the fetal heart rate (FHR) accelerations (ACC), usually considered a sign of fetal well-being; and decelerations (DEC), some of which may indicate the risk of fetal hypoxia. Thus, ACC and DEC are usually considered independent phenomena possibly providing opposite information on the fetus clinical status. CTG is typically analyzed by visual inspection; still a computerized analysis may provide a more objective CTG interpretation and precise ACC and DEC characterization. Aim of the present study is to propose an automatic procedure for ACC and DEC identification and characterization, and to investigate a potential relationship between their occurrence. The 552 tracings of the Physionet “CTU-CHB intra-partum CTG database” were analyzed according to a procedure that includes: FHR pre-processing; 20 min windowing; baseline estimation; and ACC and DEC identification and characterization. Specifically, ACC and DEC were defined as FHR deviations from baseline of at least 15 bpm for at least 15 s and then characterized in terms of length (s), amplitude (bpm) and area (length·amplitude; bpm·s). Only 383 (69.4%) CTG recordings showed sufficiently good FHR signal quality to be enrolled in the study. Number of DEC per window was significantly higher than ACC (4.0 vs 2.5; P<10-14). DEC were characterized by a comparable length but higher amplitude and area than ACC (LNG: 56 s vs 61 s, P=0.2573; AMP: 12 bpm vs 10 bpm, P<10-11; AREA: 688 s·bpm vs 618 s·bpm, P=0.0032). DEC total area in a 20-min window was higher than that of ACC (3074 s·bpm vs 2007 s·bpm, P<10-9), but such areas were also strictly correlated (ρ=0.72; P<10-62). Thus, in a CTG recording, ACC and DEC are not independent phenomena but their occurrence is strictly associated.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/250213 Collegamento a IRIS

2017 Ankle muscles co-activation patterns during normal gait: An amplitude evaluation
IFMBE Proceedings
Autore/i: Cardarelli, S.; Gentili, A.; Mengarelli, A.; Verdini, F.; Fioretti, S.; Burattini, L.; Di Nardo, F
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The objective of this work was to quantify co-activations of ankle muscles during able-bodied walking, in terms of amplitude values of surface electromyographic signal (sEMG). Gastrocnemius lateralis (GL) was analyzed as representative muscles for plantar-flexion. Tibialis anterior (TA) was analyzed as representative muscles for dorsi-flexion. Rudolph’s dynamic co-activation index was computed on the sEMG acquired from 182 strides, with the aim of quantifying the ankle-muscles co-contraction amplitude. Four different co-activations between GL and TA were observed during Heel strike (HS), Foot contact (FC), Push-off (PO), and Swing (SW), respectively. No differences were detected in time-duration of co-contractions detected in the different phases (p<0.05). TA/GL co-contraction activity is more intense in stance phase (especially during HS and FC), where a more intensive muscular control is needed for weight-support and Center of pressure (COP) progression. Co-contractions in swing phase are more frequent but milder. SW co-contraction in adults was pointed out only recently; to our knowledge, the present work is the first that quantifies it in terms of absolute and comparative amplitude. PO seems to be a transitory phase between high-level (HS and FC) and low-level (SW) co-contraction intensity regions. Present findings could be useful for deepening the physiological interpretation of ankle muscles co-activity during walking.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/250216 Collegamento a IRIS

2017 A new parameter for quantifying the variability of surface electromyographic signals during gait: The occurrence frequency
JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY
Autore/i: DI NARDO, Francesco; Mengarelli, Alessandro; Strazza, Annachiara; Agostini, Valentina; Knaflitz, Marco; Burattini, Laura; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: Natural variability of myoelectric activity during walking was recently analyzed considering hundreds of strides. This allowed assessing a parameter seldom considered in classic surface EMG (sEMG) studies: the occurrence frequency, defined as the frequency each muscle activation occurs with, quantified by the number of strides when a muscle is recruited with that specific activation modality. Aim of present study was to propose the occurrence frequency as a new parameter for assessing sEMG-signal variability during walking. Aim was addressed by processing sEMG signals acquired from Gastrocnemius Lateralis, Tibialis Anterior, Rectus Femoris and Biceps femoris in 40 healthy subjects in order to: (1) show that occurrence frequency is not correlated with ON/OFF instants (Rmean = 0.11 ± 0.07; P > 0.05) and total time of activation (Rmean = 0.15 ± 0.08; P > 0.05); (2) confirm the above results by two handy examples of application (analysis of gender and age) which highlighted that significant (P < 0.05) gender-related and age-related differences within population were detected in occurrence frequency, but not in temporal sEMG parameters. In conclusion, present study demonstrated that occurrence frequency is able to provide further information, besides those supplied by classical temporal sEMG parameters and thus it is suitable to complement them in the evaluation of variability of myoelectric activity during walking.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/250212 Collegamento a IRIS

2017 Surface-EMG analysis for the quantification of thigh muscle dynamic co-contractions during normal gait
GAIT & POSTURE
Autore/i: Strazza, Annachiara; Mengarelli, Alessandro; Fioretti, Sandro; Burattini, Laura; Agostini, Valentina; Knaflitz, Marco; Di Nardo, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: The research purpose was to quantify the co-contraction patterns of quadriceps femoris (QF) vs. hamstring muscles during free walking, in terms of onset-offset muscular activation, excitation intensity, and occurrence frequency. Statistical gait analysis was performed on surface-EMG signals from vastus lateralis (VL), rectus femoris (RF), and medial hamstrings (MH), in 16315 strides walked by 30 healthy young adults. Results showed full superimpositions of MH with both VL and RF activity from terminal swing, 80 to 100% of gait cycle (GC), to the successive loading response (≈0–15% of GC), in around 90% of the considered strides. A further superimposition was detected during the push-off phase both between VL and MH activation intervals (38.6 ± 12.8% to 44.1 ± 9.6% of GC) in 21.9 ± 13.6% of strides, and between RF and MH activation intervals (45.9 ± 5.3% to 50.7 ± 9.7 of GC) in 32.7 ± 15.1% of strides. These findings led to identify three different co-contractions among QF and hamstring muscles during able-bodied walking: in early stance (in ≈90% of strides), in push-off (in 25–30% of strides) and in terminal swing (in ≈90% of strides). The co-contraction in terminal swing is the one with the highest levels of muscle excitation intensity. To our knowledge, this analysis represents the first attempt for quantification of QF/hamstring muscles co-contraction in young healthy subjects during normal gait, able to include the physiological variability of the phenomenon.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240027 Collegamento a IRIS

2017 AThrIA: A new adaptive threshold identification algorithm for electrocardiographic P Waves
Computing in Cardiology
Autore/i: Sbrollini, Agnese; Mercanti, Sofia; Agostinelli, Angela; Morettini, Micaela; Di Nardo, Francesco; Fioretti, Sandro; Burattini, Laura
Editore: IEEE Computer Society
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Proposed algorithms for P-wave identification and segmentation usually search for it within a window just before the R peak, thus hypothesizing the presence of at most one P wave, as it is in a normal electrocardiographic (ECG) tracings. In presence of abnormal atrial depolarization, however, there might be no P waves (as in atrial fibrillation) or multiple P waves (as in second- or third-degree atrioventricular blocks). Thus, this study proposes a new Adaptive Threshold Identification Algorithm (AThrIA) for ECG P-waves whose most innovative feature is to look for P waves all along the heartbeat, potentially allowing multiple Pwaves identification. AThrIA ability to identify and segment (finding onset, maximum and offset) P waves was tested in simulated and experimental ECG tracings with no P waves, one P wave and two P waves, respectively. All P waves involved in the study were annotated. Results indicate that AThrIA correctly identified all P waves (no false-negative or false-positive detections). Segmentation errors were 0 ms for the simulated ECG tracings, and no more than 10 ms for the experimental tracings. Thus, AThrIA represents a promising tool for P-wave identification and segmentation in both physiological (one P wave) and pathological (none or multiple P waves) conditions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/259393 Collegamento a IRIS

2017 Time-frequency analysis of surface EMG signals for maximum energy localization during walking
IFMBE Proceedings
Autore/i: Strazza, A.; Verdini, F.; Burattini, L.; Fioretti, S.; Di Nardo, F
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The purpose of this work is to assess the maximum energy localization in time-frequency domain of the surface EMG signal of the main lower-limb muscles usually involved in able-bodied walking. The maximum energy localization in time-frequency domain has been identified by means of Continuous Wavelet Transform (CWT), a time-scale analysis method for multiresolution decomposition of continuous-time signals. WT coefficients allowed to reconstruct the scalogram function, providing an estimate of the local time-frequency energy density of a signal. Then, localization of maximum energy density has been identified as the interval in time-frequency where the scalogram is exceeding the 72% of the peak value of energy density in both time and frequency domain. Results showed that the localization of maximum signal energy in time coincided with the region of maximum muscle recruitment during walking. A common frequency band of maximum information content was identified for all muscles between 70 and 160 Hz. These findings could be suitable for both supporting the use of WT for sEMG analysis and providing clinical indications on muscle recruitment during walking.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/250224 Collegamento a IRIS

2017 Gait asymmetry in Winters’ group I hemiplegic children
IFMBE Proceedings
Autore/i: Di Nardo, Francesco; Agostini, V.; Strazza, A.; Nascimbeni, A.; Knaflitz, M.; Burattini, L.; Fioretti, S.
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Hemiplegia is a neurological disorder that in children is a common consequence of cerebral palsy. Hemiplegia involves one-half of the body, while the other half is typically not affected. Aim of the study was to evaluate gait asymmetry in Winters’ group I hemiplegic children (W1), by identifying possible differences between hemiplegic and non-hemiplegic side in foot-floor contact and activation patterns of gastrocnemius lateralis (GL). To this aim, basographic and EMG data from 12 hemiplegic cerebral palsy children (Winters’ group I) were analyzed. Gait data from 100 normal developing children were used as reference. Mean decrease (p<0.05) of normal cycles (i.e. normal sequence of gait phases HFPS) and a concomitant increase (p<0.05) of atypical cycles (PFPS) were detected in hemiplegic side of W1, with respect to both non-hemiplegic side and control group. No relevant variations of GL recruitment were observed between hemiplegic and non-hemiplegic side of W1, in terms of muscle activation patterns and occurrence frequency. In conclusion, the study suggested that gait asymmetries detected in W1 lie in foot-floor contact patterns, but not in GL recruitment.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/250215 Collegamento a IRIS

2017 Separation of superimposed electrocardiographic and electromyographic signals
IFMBE Proceedings
Autore/i: SBROLLINI, AGNESE; AGOSTINELLI, ANGELA; MORETTINI, MICAELA; VERDINI, Federica; DI NARDO, Francesco; FIORETTI, Sandro; BURATTINI, LAURA
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Electrocardiography (ECG) and surface electromyography (SEMG) are two non-invasive tests to evaluate cardiac and muscular functionality, respectively. They are both acquired by placing electrodes on the body surface so they become one the interference of the other. Typically, linear filters are used for ECG and SEMG separation: high-pass filters with cutoff at 20 Hz to attenuate ECG interference in SEMG, and low-pass filters with cut-off at 50 Hz to attenuate SEMG interference in ECG. In spite of that, linear filtering is not adequate due to the presence of a 20-50 Hz frequency-band in which the two signal spectra overlap. The aim of the present study was to evaluate the ability of the Segmented-Beat Modulation Method (SBMM) for ECG and SEMG separation and by accurately maintaining signals characteristics. SBMM is a template-based technique for ECG denoising: under the hypothesis of ECG and SEMG linearly superimposed, it first provides an ECG estimation, and then an SEMG estimation by subtraction. In order to test the method under several conditions, SBMM was applied to simulated as well as clinical recordings with superimposed ECG and SEMG. SBMM was able to accurately estimate both ECG and SEMG in all cases. Indeed, ECG and SEMG were estimated by maintain their features such as amplitude (estimation errors <6%), heart rate and heart-rate variability. Moreover, estimated ECG was always characterized by a spectrum mostly (76.4-100.0%) included in the 0-50 Hz frequency-band, whereas estimated SEMG was always characterized by a spectrum mostly (80.9-95.6%) included in the 20-450 Hz frequency-band. Such results confirm the existence of a 20-50 Hz frequency-band in which ECG and SEMG spectral components are overlapped. Thus, SBMM is a robust filtering procedure to separate superimposed ECG and SEMG.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/250221 Collegamento a IRIS

2017 Co-contraction activity of ankle muscles during walking: A gender comparison
BIOMEDICAL SIGNAL PROCESSING AND CONTROL
Autore/i: Mengarelli, Alessandro; Maranesi, Elvira; Burattini, Laura; Fioretti, Sandro; Di Nardo, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: The study aimed to assess possible differences between healthy, young males and females in co-contraction activity of tibialis anterior and gastrocnemius lateralis during gait at self-selected speed and cadence. The Statistical-Gait-Analysis methodology, allowing a statistical characterization of gait by averaging spatial-temporal and sEMG-based parameters over hundreds of strides per walking trial, was applied on thirty age-matched subjects: 15 males and 15 females. Co-contractions were assessed as the overlapping periods between muscular activities. Results showed the occurrence of four different co-contractions during gait cycle, for both groups. No significant differences in activation instants (ON-OFF) were detected between groups. Otherwise, all the co-contractions occurred in higher number of strides (%) in females, respect to males: in early stance (40.7 ± 18.7% vs. 18.9 ± 11.0%, p < 0.001), mid-stance (41.5 ± 15.2% vs. 26.0 ± 22.8%, p < 0.005), pre-swing (16.6 ± 7.3% vs. 7.1 ± 4.7%, p < 0.001), and swing (79.4 ± 13.7% vs. 55.6 ± 19.3%, p < 0.001). This overall higher occurrence of ankle-muscle co-contractions, associated to a more complex muscular recruitment, seems to reflect a female need for a higher level of ankle-joint stabilization. Thus, present findings indicated gender as a not negligible factor in the interpretation of muscular co-contraction variability during walking and suggested the suitability of gender-based approaches in clinical studies and in developing reference frameworks.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/241694 Collegamento a IRIS

2017 CTG Analyzer: A graphical user interface for cardiotocography
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Sbrollini, Agnese; Agostinelli, Angela; Burattini, Luca; Morettini, Micaela; Di Nardo, Francesco; Fioretti, Sandro; Burattini, Laura
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Cardiotocography (CTG) is the most commonly used test for establishing the good health of the fetus during pregnancy and labor. CTG consists in the recording of fetal heart rate (FHR; bpm) and maternal uterine contractions (UC; mmHg). FHR is characterized by baseline, baseline variability, tachycardia, bradycardia, acceleration and decelerations. Instead, UC signal is characterized by presence of contractions and contractions period. Such parameters are usually evaluated by visual inspection. However, visual analysis of CTG recordings has a well-demonstrated poor reproducibility, due to the complexity of physiological phenomena affecting fetal heart rhythm and being related to clinician's experience. Computerized tools in support of clinicians represents a possible solution for improving correctness in CTG interpretation. This paper proposes CTG Analyzer as a graphical tool for automatic and objective analysis of CTG tracings. CTG Analyzer was developed under MATLAB®; it is a very intuitive and user friendly graphical user interface. FHR time series and UC signal are represented one under the other, on a grid with reference lines, as usually done for CTG reports printed on paper. Colors help identification of FHR and UC features. Automatic analysis is based on some unchangeable features definitions provided by the FIGO guidelines, and other arbitrary settings whose default values can be changed by the user. Eventually, CTG Analyzer provides a report file listing all the quantitative results of the analysis. Thus, CTG Analyzer represents a potentially useful graphical tool for automatic and objective analysis of CTG tracings.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/255424 Collegamento a IRIS

2017 CaRiSMA 1.0: Cardiac risk self-monitoring assessment
THE OPEN SPORTS SCIENCES JOURNAL
Autore/i: Agostinelli, Angela; Morettini, Micaela; Sbrollini, Agnese; Maranesi, Elvira; Migliorelli, Lucia; Di Nardo, Francesco; Fioretti, Sandro; Burattini, Laura
Classificazione: 1 Contributo su Rivista
Abstract: Background: Sport-related sudden cardiac death (SRSCD) can only be fought through prevention. Objective: The aim of this study is to propose an innovative software application, CaRiSMA 1.0 (Cardiac Risk Self-Monitoring Assessment), as a potential tool to help contrasting SRSCD and educating to a correct training. Methods: CaRiSMA 1.0 analyzes the electrocardiographic and heart-rate (HR) signals acquired during a training session through wearable sensors and provides intuitive graphical outputs consisting of two traffic lights, one related to cardiac health, based on resting QTc (a parameter quantifying the duration of ventricular contraction and subsequent relaxation), and one related to training, based on exercise HR. Safe and worthwhile training sessions have green traffic lights. A red QTc traffic light indicates the need of a medical consultation, whereas a red HR traffic light indicate the need of a reduction of training intensity. By way of example, CaRiSMA 1.0 was applied to sample data acquired in 10 volunteers (age= 27±11 years; males/females 3/7). Results: Two acquisitions (20.0%) were rejected because too noisy, indicating that wearable sensors may record poor quality signals. The QTc traffic light was red in 1 case, indicating that people practicing sport may not be aware of being at risk. The HR traffic light was red in 0 cases. Conclusion: CaRiSMA 1.0 is a software application that, for the first time in the sport context, uses QTc, the most important index of cardiac risk in clinics. Thus, it has the potential for giving a contribution in the fight against SRSCD.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/252423 Collegamento a IRIS

2017 Acellular dermal matrix and heel reconstruction: a new prospective
JOURNAL OF APPLIED BIOMATERIALS & FUNCTIONAL MATERIALS
Autore/i: Scalise, Alessandro; Torresetti, Matteo; Verdini, Federica; Capecci, Marianna; Andrenelli, Elisa; Mengarelli, Alessandro; Ceravolo, MARIA GABRIELLA; Fioretti, Sandro; DI BENEDETTO, GIOVANNI MARIA
Classificazione: 1 Contributo su Rivista
Abstract: Heel reconstruction represents a challenge for all plastic surgeons due to the anatomical and functional features of this weight-bearing area. In the last decade a combined use of acellular dermal matrices and skin grafts has been proposed as a reliable and less invasive alternative for complex wound management; nevertheless only a few cases have been reported in the literature.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/249780 Collegamento a IRIS

2017 Noninvasive Fetal Electrocardiography Part II: Segmented-Beat Modulation Method for Signal Denoising
THE OPEN BIOMEDICAL ENGINEERING JOURNAL
Autore/i: AGOSTINELLI, ANGELA; SBROLLINI, AGNESE; Burattini, Luca; FIORETTI, Sandro; DI NARDO, Francesco; BURATTINI, LAURA
Classificazione: 1 Contributo su Rivista
Abstract: Background: Fetal well-being evaluation may be accomplished by monitoring cardiac activity through fetal electrocardiography. Direct fetal electrocardiography (acquired through scalp electrodes) is the gold standard but its invasiveness limits its clinical applicability. Instead, clinical use of indirect fetal electrocardiography (acquired through abdominal electrodes) is limited by its poor signal quality. Objective: Aim of this study was to evaluate the suitability of the Segmented-Beat Modulation Method to denoise indirect fetal electrocardiograms in order to achieve a signal-quality at least comparable to the direct ones. Method: Direct and indirect recordings, simultaneously acquired from 5 pregnant women during labor, were filtered with the Segmented-Beat Modulation Method and correlated in order to assess their morphological correspondence. Signal-to-noise ratio was used to quantify their quality. Results: Amplitude was higher in direct than indirect fetal electrocardiograms (median:104 µVvs. 22 µV; P=7.66·10-4), whereas noise was comparable (median:70 µV vs. 49 µV, P=0.45). Moreover, fetal electrocardiogram amplitude was significantly higher than affecting noise in direct recording (P=3.17·10-2) and significantly in indirect recording (P=1.90·10-3). Consequently, signal-to-noise ratio was initially higher for direct than indirect recordings (median:3.3 dB vs. -2.3 dB; P=3.90·10-3), but became lower after denoising of indirect ones (median:9.6 dB; P=9.84·10-4). Eventually, direct and indirect recordings were highly correlated (median: ρ=0.78; P<10-208), indicating that the two electrocardiograms were morphologically equivalent. Conclusion: Segmented-Beat Modulation Method is particularly useful for denoising of indirect fetal electrocardiogram and may contribute to the spread of this noninvasive technique in the clinical practice.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/246940 Collegamento a IRIS

2017 Noninvasive Fetal Electrocardiography Part I: Pan-Tompkins' Algorithm Adaptation to Fetal R-peak Identification
THE OPEN BIOMEDICAL ENGINEERING JOURNAL
Autore/i: AGOSTINELLI, ANGELA; Marcantoni, Ilaria; Moretti, Elisa; SBROLLINI, AGNESE; FIORETTI, Sandro; DI NARDO, Francesco; BURATTINI, LAURA
Classificazione: 1 Contributo su Rivista
Abstract: Background: Indirect fetal electrocardiography is preferable to direct fetal electrocardiography because of being noninvasive and is applicable also during the end of pregnancy, besides labor. Still, the former is strongly affected by noise so that even R-peak detection (which is essential for fetal heart-rate evaluations and subsequent processing procedures) is challenging. Some fetal studies have applied the Pan-Tompkins’ algorithm that, however, was originally designed for adult applications. Thus, this work evaluated the PanTompkins’ algorithm suitability for fetal applications, and proposed fetal adjustments and optimizations to improve it. Method: Both Pan-Tompkins’ algorithm and its improved version were applied to the “Abdominal and Direct Fetal Electrocardiogram Database” and to the “Noninvasive Fetal Electrocardiography Database” of Physionet. R-peak detection accuracy was quantified by computation of positive-predictive value, sensitivity and F1 score. Results: When applied to “Abdominal and Direct Fetal Electrocardiogram Database”, the accuracy of the improved fetal Pan-Tompkins’ algorithm was significantly higher than the standard (positive-predictive value: 0.94 vs. 0.79; sensitivity: 0.95 vs. 0.80; F1 score: 0.94 vs. 0.79; P<0.05 in all cases) on indirect fetal electrocardiograms, whereas both methods performed similarly on direct fetal electrocardiograms (positive-predictive value, sensitivity and F1 score all close to 1). Improved fetal Pan-Tompkins’ algorithm was found to be superior to the standard also when applied to “Noninvasive Fetal Electrocardiography Database” (positive-predictive value: 0.68 vs. 0.55, P<0.05; sensitivity: 0.56 vs. 0.46, P=0.23; F1 score: 0.60 vs. 0.47, P=0.11). Conclusion: In indirect fetal electrocardiographic applications, improved fetal Pan-Tompkins’ algorithm is to be preferred over the standard, since it provides higher R-peak detection accuracy for heart-rate evaluations and subsequent processing.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/246939 Collegamento a IRIS

2017 Heart Rate Detection Using Microsoft Kinect: Validation and Comparison to Wearable Devices
SENSORS
Autore/i: Gambi, Ennio; Agostinelli, Angela; Belli, Alberto; Burattini, Laura; Cippitelli, Enea; Fioretti, Sandro; Pierleoni, Paola; Ricciuti, Manola; Sbrollini, Agnese; Spinsante, Susanna
Classificazione: 1 Contributo su Rivista
Abstract: Contactless detection is one of the new frontiers of technological innovation in the field of healthcare, enabling unobtrusive measurements of biomedical parameters. Compared to conventional methods for Heart Rate (HR) detection that employ expensive and/or uncomfortable devices, such as the Electrocardiograph (ECG) or pulse oximeter, contactless HR detection offers fast and continuous monitoring of heart activities and provides support for clinical analysis without the need for the user to wear a device. This paper presents a validation study for a contactless HR estimation method exploiting RGB (Red, Green, Blue) data from a Microsoft Kinect v2 device. This method, based on Eulerian Video Magnification (EVM), Photoplethysmography (PPG) and Videoplethysmography (VPG), can achieve performance comparable to classical approaches exploiting wearable systems, under specific test conditions. The output given by a Holter, which represents the gold-standard device used in the test for ECG extraction, is considered as the ground-truth, while a comparison with a commercial smartwatch is also included. The validation process is conducted with two modalities that differ for the availability of a priori knowledge about the subjects' normal HR. The two test modalities provide different results. In particular, the HR estimation differs from the ground-truth by 2% when the knowledge about the subject's lifestyle and his/her HR is considered and by 3.4% if no information about the person is taken into account.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/250486 Collegamento a IRIS

2017 Is child walking conditioned by gender? Surface EMG patterns in female and male children
GAIT & POSTURE
Autore/i: Di Nardo, Francesco; Laureati, Giulio; Strazza, Annachiara; Mengarelli, Alessandro; Burattini, Laura; Agostini, Valentina; Nascimbeni, Alberto; Knaflitz, Marco; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: EMG-based differences between females and males during walking are generally acknowledged in adults. Aim of the study was the quantification of possible gender differences in myoelectric activity of gastrocnemius lateralis (GL) and tibialis anterior (TA) during walking in school-age children. Gender-related comparison with adults was also provided to get possible novel insight in maturation of gait. To this aim, Statistical gait analysis, a recent methodology performing a statistical characterization of gait by averaging spatial-temporal and surface-EMG-based parameters over hundreds of strides, was performed in100 healthy school-age children (C-group) and in 33 healthy young adults (YA-group). On average, 301±110 consecutive strides were analyzed for each subject. In C-group, no significant differences (p>0.05) were observed between females and males in GL and TA, considering mean onset/offset instants of activation and occurrence frequency. Stratifying the C-group for age, small differences between females and males in occurrence frequency of GL arose in oldest children. In YA-group, females showed a significant propensity for a more complex recruitment of TA and GL (higher number of activations during gait cycle, quantified by occurrence frequency) compared to males. These outcomes suggest that gender-related differences in sEMG parameters do not characterize the recruitment of GL and TA during child walking in early years (6-8 years), start occurring when adolescence is approaching (10-12 years), and are acknowledged in both ankle muscles only in adults. Present findings seem to support previous studies on maturation of gait which indicate adolescence as the time-range where gait is completing its maturation path.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/245755 Collegamento a IRIS

2017 IVGTT-based simple assessment of glucose tolerance in the Zucker fatty rat: Validation against minimal models
PLOS ONE
Autore/i: MORETTINI, MICAELA; Faelli, Emanuela; Perasso, Luisa; FIORETTI, Sandro; BURATTINI, LAURA; Ruggeri, Piero; DI NARDO, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: For the assessment of glucose tolerance from IVGTT data in Zucker rat, minimal model methodology is reliable but time- and money-consuming. This study aimed to validate for the first time in Zucker rat, simple surrogate indexes of insulin sensitivity and secretion against the glucose-minimal-model insulin sensitivity index (SI) and against first- (φ1) and second-phase (φ2) β-cell responsiveness indexes provided by C-peptide minimal model. Validation of the surrogate insulin sensitivity index (ISI) and of two sets of coupled insulinbased indexes for insulin secretion, differing from the cut-off point between phases (FPIR3- SPIR3, t = 3 min and FPIR5- SPIR5, t = 5 min), was carried out in a population of ten Zucker fatty rats (ZFR) and ten Zucker lean rats (ZLR). Considering the whole rat population (ZLR+ZFR), ISI showed a significant strong correlation with SI (Spearman's correlation coefficient, r = 0.88; P<0.001). Both FPIR3 and FPIR5 showed a significant (P<0.001) strong correlation with φ1 (r = 0.76 and r = 0.75, respectively). Both SPIR3 and SPIR5 showed a significant (P<0.001) strong correlation with φ2 (r = 0.85 and r = 0.83, respectively). ISI is able to detect (P<0.001) the well-recognized reduction in insulin sensitivity in ZFRs, compared to ZLRs. The insulin-based indexes of insulin secretion are able to detect in ZFRs (P<0.001) the compensatory increase of first- and second-phase secretion, associated to the insulinresistant state. The ability of the surrogate indexes in describing glucose tolerance in the ZFRs was confirmed by the Disposition Index analysis. The model-based validation performed in the present study supports the utilization of low-cost, insulin-based indexes for the assessment of glucose tolerance in Zucker rat, reliable animal model of human metabolic syndrome.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/245897 Collegamento a IRIS

2016 A markerless system based on smartphones and webcam for the measure of step length, width and duration on treadmill
COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE
Autore/i: Barone, Vinicio; Verdini, Federica; Burattini, Laura; Di Nardo, Francesco; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: Background and objective: A markerless low cost prototype has been developed for the deter-mination of some spatio-temporal parameters of human gait: step-length, step-width andcadence have been considered. Only a smartphone and a high-definition webcam have beenused.Methods: The signals obtained by the accelerometer embedded in the smartphone are usedto recognize the heel strike events, while the feet positions are calculated through imageprocessing of the webcam stream. Step length and width are computed during gait trials ona treadmill at various speeds (3, 4 and 5 km/h).Results: Six subjects have been tested for a total of 504 steps. Results were compared withthose obtained by a stereo-photogrammetric system (Elite, BTS Engineering). The maximumaverage errors were 3.7 cm (5.36%) for the right step length and 1.63 cm (15.16%) for the rightstep width at 5 km/h. The maximum average error for step duration was 0.02 s (1.69%) at5 km/h for the right steps.Conclusion: The system is characterized by a very high level of automation that allows itsuse by non-expert users in non-structured environments. A low cost system able to auto-matically provide a reliable and repeatable evaluation of some gait events and parametersduring treadmill walking, is relevant also from a clinical point of view because it allows theanalysis of hundreds of steps and consequently an analysis of their variability.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/230084 Collegamento a IRIS

2016 Predictive Power of f99 Repolarization Index for the Occurrence of Ventricular Arrhythmias
ANNALS OF NONINVASIVE ELECTROCARDIOLOGY
Autore/i: Corrado, Giuliani; Cees, A. Swenne M. D.; Sumche Man, M. D; AGOSTINELLI, ANGELA; FIORETTI, Sandro; DI NARDO, Francesco; BURATTINI, LAURA
Classificazione: 1 Contributo su Rivista
Abstract: Background.Defects of cardiac repolarization, noninvasively identifiable by analyzing the electrocardiographic (ECG) ST segment and T wave, are among the major causes of sudden cardiac death. Still, no repolarization-based index has so far shown sufficient sensitivity and specificity to justify preventive treatments. Thus, the aim of this work was to evaluate the predictive power of our recently proposed f99 index for the occurrence of ventricular arrhythmias. Methods. Our study populations included 170 patients with implanted cardiac defibrillator (ICD), 44 of which developed ventricular tachycardia and/or fibrillation during the 4-year follow-up (ICD_Cases) and 126 did not (ICD_Controls). The f99 index, defined as the frequency at which the repolarization normalized cumulative energy reaches 99%, was computed in each of the 15 (I to III, aVl, aVr, aVf, V1–V6, X, Y, Z) available ECG leads independently, and then maximized over the 6 precordial leads (f99_MaxV1–V6), 12 standard leads (f99_Max12STD) and three orthogonal leads (f99_MaxXYZ) to avoid dispersion-related issues. Each index predictive power was quantified as the area under the receiving operating characteristic curve (AUC). Results.Median f99_MaxV1–V6, f99_Max12STD and f99_MaxXYZ values were significantly higher in the ICD_Cases than in the ICD_Controls (48 Hz vs. 35 Hz, P<0.05; 51 Hz vs. 43 Hz, P<0.05; 45 Hz vs. 31 Hz, P<10−3; respectively), indicating a more fragmented repolarization in the former group. The AUC values were 0.62, 0.63 and 0.68, respectively. Conclusions.The f99 represents a promising risk index for the occurrence of ventricular arrhythmias, especially when maximized over the three orthogonal leads.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/234896 Collegamento a IRIS

2016 Normative EMG patterns of ankle muscle co-contractions in school-age children during gait
GAIT & POSTURE
Autore/i: Di Nardo, Francesco; Mengarelli, Alessandro; Burattini, Laura; Maranesi, Elvira; Agostini, Valentina; Nascimbeni, Alberto; Knaflitz, Marco; Fioretti, Sandro
Classificazione: 1 Contributo su Rivista
Abstract: Purpose: The study was designed to assess the co-contractions of tibialis anterior (TA) and gastrocnemius lateralis (GL) in healthy school-age children during gait at self-selected speed and cadence, in terms of variability of onset-offset muscular activation and occurrence frequency. Methods: Statistical gait analysis, a recent methodology performing a statistical characterization of gait by averaging spatio-temporal and sEMG-based parameters over numerous strides, was performed in 100 healthy children, aged 6-11 years. Co-contractions were assessed as the period of overlap between activation intervals of TA and GL. Results: On average, 165 ± 27 strides were analyzed for each child, resulting in approximately 16,500 strides. Results showed that GL and TA act as pure agonist/antagonists for ankle plantar/dorsiflexion (no co-contractions) in only 19.2 ± 10.4% of strides. In the remaining strides, statistically significant (p < 0.05) co-contractions appear in early stance (46.5 ± 23.0% of the strides), mid-stance (28.8 ± 15.9%), pre-swing (15.2 ± 9.2%), and swing (73.2 ± 22.6%). This significantly increased complexity in muscle recruitment strategy beyond the activation as pure ankle plantar/dorsiflexors, suggests that in healthy children co-contractions are likely functional to further physiological tasks as balance improvement and control of joint stability. Conclusions: This study represents the first attempt for the development in healthy children of a normative dataset for GL/TA co-contractions during gait, achieved on an exceptionally large number of strides in every child and in total. The present reference frame could be useful for discriminating physiological and pathological behavior in children and for designing more focused studies on the maturation of gait.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/234881 Collegamento a IRIS

2016 Are the rectus femoris and the vastus lateralis concurrently recruited during walking?
IFMBE Proceedings
Autore/i: Di Nardo, Francesco; Mengarelli, A.; Strazza, A.; Maranesi, E.; Burattini, L.; Fioretti, S.
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The aim of the study was the quantitative assessment of the concomitant recruitment of rectus femoris (RF) and vastus lateralis (VL) in a group of 11 healthy young adults during walking. To this aim, Statistical gait analysis, a recent methodology performing a statistical characterization of gait by averaging spatial-temporal and surface-EMG-based parameters over numerous strides, was performed in each subject. Superimpositions between RF and VL activity were detected from terminal swing to the following loading response in 99.0±25.8% of strides. This superimposition could be intended as a synergic action of the two muscles for controlling weight bearing, to assist knee extension and to control knee flexion. A further infrequent (<5% of the strides) superimposition was detected in mid and terminal stance, suggesting that the two muscles are working on different joints: RF activity could be interpreted as active participation in hip flexion, while VL activity as the main contribution in modulating rapid knee flexion. These findings have the merit to provide a novel data on the variability of the reciprocal role of RF and VL during walking, allowing a deeper insight in the physiological mechanisms that regulate the knee flexion/extension.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236250 Collegamento a IRIS

2016 Activation pattern of Extensor digitorum brevis muscle during child walking
Proceeding of the 8th International workshop on Biosignal Interpretation
Autore/i: Strazza A; Palmieri MS; Mengarelli A; Fioretti S; Burattini L; Orsini O; Bortone A; Di Nardo F
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The purpose of the study was the assessment of the activation pattern of Extensor digitorum brevis (EDB) muscle in healthy children, during walking at self-selected speed and cadence. To this aim, the Statistical Gait Analysis was performed on surface electromyographic (sEMG) signals, in a large number (hundreds) of strides per subject. Results from eight healthy children showed a large variability in number of muscle activations, occurrence frequency, and onset-offset instants across strides analyzed. The assessment of the different modalities of activation allowed identifying a single activity pattern, common for all the modalities and able to characterize the behavior of EDB during normal gait. The pattern of muscle activity centered in two main regions of the gait cycle: the second half of the stance phase (detected in 100% of the subjects) and in final swing phase (50%). This ‘‘normality’’ pattern represents the first attempt to develop a reference for dynamic sEMG of EDB in healthy children that is able to include the physiological variability of the phenomenon. The present results could be useful for discriminating physiological and pathological behavior in children and for deepening the maturation of gait.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247674 Collegamento a IRIS

2016 Relationship between Deceleration Areas in the Second Stage of Labor and Neonatal Acidemia
Computing in Cardiology 2016
Autore/i: AGOSTINELLI, ANGELA; Palmieri, Flavio; BIAGINI, ALESSANDRA; SBROLLINI, AGNESE; Burattini, Luca; DI NARDO, Francesco; FIORETTI, Sandro; BURATTINI, LAURA
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Understanding the fetal heart rate (FHR) in the second stage of labor is important to recognize critical clinical outcomes. During this time, fetus is subject to head compression that activate baroreceptor reflexes that cause FHR deceleration. Large deceleration areas (DA: measured as duration by depth), have been associated to critical fetal outcomes. A preliminary study on 33 pregnant women reported a significant inverse correlation between DA in the last 60 minutes before delivery and umbilical pH at birth (fetal-distress measure when < 7.1). The aim of this study is to further characterize the relationship between DA in the last 60 minutes before delivery and pH at birth on a larger population. Thus, 433 FHR recordings from the 'CTU-CHB Intrapartum Cardiotocography Database' of Physionet were used. Signals were classified as Cases (pH < 7.1) and Controls (pH > 7.1). Results confirmed that Cases have significantly higher DA than Controls (5.32 cm2 vs 1.44 cm2; P < 0.05). The inverse correlation between DA in the last 60 minutes before delivery and pH at birth, was weak but significant (ρ=-0.23, P<10-6). Thus, results confirm that critical fetal outcomes increase with increasing acidemia; however, such relationship may not be strictly linear. Future studies are focused on discrimination of fetal distress using DA.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/246949 Collegamento a IRIS

2016 Validation of the Heart-Rate Signal Provided by the Zephyr BioHarness 3.0
Computing in Cardiology 2016
Autore/i: Nepi, Daniele; Sbrollini, Agnese; Agostinelli, Angela; Maranesi, Elvira; Morettini, Micaela; Di Nardo, Francesco; Fioretti, Sandro; Pierleoni, Paola; Pernini, Luca; Valenti, Simone; Burattini, Laura
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The Zephyr BioHarness 3.0 (BH3) is a popular wearable system specifically designed for training optimization of professional athletes. BH3 provides the electrocardiogram (ECG BH3) and the heart-rate signal (HRSBH3). Aim of this study is to evaluate the reliability of HRSBH3 to assess its clinical applicability to the general population for cardiac-risk evaluations. Data were acquired from 10 healthy subjects (age: 34±17 years) during a 5-minutes rest. Since the tachogram represents the standard signal for studying the heart rate (HR) and its variability, ECG BH3 was elaborated in order to get the tachogram (HRSTG). HRSBH3 and HRSTG were compared in terms of mean HR (MHR, bpm), HR standard deviation (HRSD, bpm) and HRSD error (bpm). HRSBH3 and HRSTG provided comparable MHR (73.07±15.53 bpm vs 72.86±15.57 bpm, respectively) while HRSD by HRSBH3 was significantly lower than HRSD by HRS TG (4.51 ±2.29 bpm vs 5.63±2.99 bpm, respectively; P=0.0043). HRSD error was significantly greater than zero (0.20-3.00 bpm; P=0.0043); moreover, it was strongly correlated to HRSD by HRS TG (p=0.82, P=0.0036). Thus, HRS BH3 is appropriate only for sport applications based on MHR estimations, but not to clinical evaluations based on HRV measurements.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/246953 Collegamento a IRIS

2016 A new segmented-beat modulation algorithm for maternal ECG estimation from abdominal recordings
Lecture Notes in Electrical Engineering
Autore/i: Agostinelli, A.; Giuliani, C.; Fioretti, S.; Di Nardo, F.; Burattini, L
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Abstract: The noninvasive fetal electrocardiogram (fECG) provides precious information about the physiological fetus state. It is extracted from abdominal recordings, obtained positioning surface electrodes on the maternal abdomen, by subtraction of the maternal ECG (mECG), often roughly estimated by simply concatenating a maternal-beat template. Aim of the present study is to propose a new algorithm for the mECG estimation based on a segmented-beat modulation method (SBMM) that adjusts the template length to the maternal physiological heart-rate variability (HRV) and reduces the level of noise. According to the SBMM, each maternal cardiac cycle (CC) is segmented into two segments, QRS and TUP, respectively independent and proportional to preceding RR interval. The estimated mECG is the concatenation of the template-beat, obtained as the median of the maternal beat after modulation and demodulation of TUP segment. The algorithm was applied to two (ARec1 and ARec2) 4-channel abdominal recordings obtained from pregnant women. ARec1 and ARec2 were both 60 s long and characterized by similar heart rate (HR: 80 bpm and 82 bpm) but different HRV (42 ms vs. 139 ms). Results indicate that the error in the mECG estimation is always small (<2.5 μV) but increases with HRV (ARec1: 0.87–1.65 μV; ARec2: 1.98–2.37 μV). In conclusion, the proposed algorithm based on the SBMM allows a clean mECG estimation from abdominal recordings thanks to a modulation procedure introduced to track physiological variation in the maternal heart rhythm.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240327 Collegamento a IRIS

2016 sEMG-based evaluation of muscle recruitment variability during walking in terms of activation length and occurrence frequency
Lecture Notes in Electrical Engineering
Autore/i: Mengarelli, A.; Maranesi, E.; Burattini, L.; Fioretti, S.; Di Nardo, F
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Abstract: Surface electromyography (sEMG) is commonly used in gait analysis for detecting muscle activity in a non-invasive way, preserving the normal mobility of the subject. The purpose of the study was to assess the variability of sEMG signals acquired from lower-limb muscles during walking. To this aim, a statistical analysis of sEMG signals from a large number (hundreds) of strides per subject was performed in twenty-two healthy young caucasian volunteers. Tibialis Anterior, Gastrocnemius Lateralis, Rectus Femoris, Biceps Femoris and Vastus Lateralis were selected to represent both proximal and distal leg segments. Besides the muscular activation onset-offset instants, the study was aimed to analysed the occurrence frequency of muscle recruitment, a parameter seldom considered because of the low number of strides usually analysed in classic EMG studies. Findings illustrated that a single muscle showed a different number of activation intervals in different strides of the same walking. The number of times when muscle activates during a single gait cycle defined the modality of muscle recruitment, that in the present study was referred to as activation modality, i.e. n-activation modality consists of n-activation intervals for the considered muscle, during a single gait cycle. For each of the selected muscles, five activation modalities were detected. Each of these activation modalities is characterized by a different occurrence frequency and by different onset-offset activation instants. Concomitance of these results indicates a large variability in onset-offset muscular activation and occurrence frequency, which should be considered in discriminating pathological from physiological behaviour and for designing focused gait studies.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240328 Collegamento a IRIS

2016 The relative role of insulin action and secretion in experimental animal models of metabolic syndrome
IFMBE Proceedings
Autore/i: MORETTINI, MICAELA; DI NARDO, Francesco; Cogo, C. E.; Faelli, E.; FIORETTI, Sandro; BURATTINI, LAURA; Ruggeri, P.
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In the present study we evaluated insulin action and secretion in a group of 7 young Zucker fatty rats (ZFR), and in a group of 8 spontaneously hypertensive rats (SHR), compared with two control groups of 7 young Zucker lean rats (ZLR) and 8 Wistar Kyoto rats (WKY), respectively. Our goal is to broaden the characterization of glucose tolerance, including insulin secretion, in two animal models used for the characterization of human metabolic syndrome: the ZFR and the SHR. Reliable estimates of insulin sensitivity index, SI, was provided by minimal model analysis of IVGTT data. To characterize insulin secretion we calculated an index based on IVGTT data: AIRG, i.e. the acute insulin response after glucose bolus, related to the first phase insulin secretion. The ZFR showed a significantly (p<0.005) lower mean estimate of SI, and a significantly (p<0.001) higher mean value of AIRG, compared to control groups (ZLR and WKY) and hypertensive rats (SHR). Thus, only the ZFR shows a reduced insulin action, compensated only partially by insulin hypersecretion. This suggests obesity, with respect to hypertension, as a primary factor in the deterioration of glucose tolerance. © Springer International Publishing Switzerland 2016.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236267 Collegamento a IRIS

2016 Estimation of first-phase insulin secretion in the Zucker Fatty Rat
IFMBE Proceedings
Autore/i: DI NARDO, Francesco; MORETTINI, MICAELA; Cogo, C. E.; Faelli, E.; FIORETTI, Sandro; BURATTINI, LAURA; Ruggeri, P.
Editore: Springer Verlag
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The present study was designed to test the efficacy of the popular index AIRG(i.e. acute insulin response after glucose bolus) in the characterization of the first-phase insulin secretion in the Zucker Fatty Rat. The reliability of the AIRGwas evaluated by direct comparison with the first-phase β-cell responsiveness index (Φ1)provided by C-peptide minimal model. To this aim, AIRG and Φ1were simultaneously computed from IVGTT data, measured in six Zucker fatty rats (ZFR), 7-to-9week-old, and seven age-matched Zucker lean rats (ZLR). In the whole 13 rats population, the AIRG showed a significant linear correlation with Φ1(r = 0.89, P < 0.0001). Moreover, both Φ1(P < 0.05) and AIRG (p<0.001) showed a significant increase, in the ZFRs, compared to control group (ZLR). These findings suggest that the AIRG index is able to provide similar information of Φ1, in the evaluation of the alteration of the first-phase insulin secretion in Zucker Fatty Rats. Thus, the present study proposes the AIRG, as a suitable empiric index for a simple, reliable and low-cost quantification of the first-phase insulin secretion in Zucker Fatty Rats. © Springer International Publishing Switzerland 2016.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236266 Collegamento a IRIS

2016 Segmented beat modulation method for electrocardiogram estimation from noisy recordings
MEDICAL ENGINEERING & PHYSICS
Autore/i: AGOSTINELLI, ANGELA; SBROLLINI, AGNESE; GIULIANI, CORRADO; FIORETTI, Sandro; DI NARDO, Francesco; BURATTINI, LAURA
Classificazione: 1 Contributo su Rivista
Abstract: Clinical utility of an electrocardiogram (ECG) affected by too high levels of noise such as baseline wanders, electrode motion artifacts, muscular artifacts and power-line interference may be jeopardized if not opportunely processed. Template-based techniques have been proposed for ECG estimation from noisy recordings, but usually they do not reproduce physiological ECG variability, which, however, provides clinically useful information on the patient's health. Thus, this study proposes the Segmented-Beat Modulation Method (SBMM) as a new template-based filtering procedure able to reproduce ECG variability, and assesses SBMM robustness to the aforementioned noises in comparison to a standard template method (STM). SBMM performs a unique ECG segmentation into QRS segment and TUP segment, and successively modulates demodulates (by stretching or compressing) the former segments in order to adaptively adjust each estimated beat to its original morphology and duration. Consequently, SBMM estimates ECG with significantly lower estimation errors than STM when applied to recordings affected by various levels of the considered noises (SBMM: 176-232 mu V and 79-499 mu V; STM: 215-496 mu V and 93-1056 mu V, for QRS and TUP segments, respectively). Thus, SBMM is able to reproduce ECG variability and is more robust to noise than STM.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236052 Collegamento a IRIS

2016 The surface electromyographic evaluation of the Functional Reach in elderly subjects
JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY
Autore/i: Maranesi, E; Fioretti, S; Ghetti, G G; Rabini, R A; Burattini, L; Mercante, O; Di Nardo, F
Classificazione: 1 Contributo su Rivista
Abstract: This study proposes a comprehensive assessment of myoelectric activity of the main muscles involved in the Functional Reach (FR) test, in 24 elderly subjects. A specific protocol for the surface electromyography (sEMG) signal acquisition during FR-test was developed. Results show that anterior muscles activate following a caudo-cranial order. Tibialis Anterior (TA) is the first to be activated (-18.0±16.3% of the FR-period), together with Rectus Femoris (-10.4±17.9%). Then, Rectus Abdominis (19.7±24.7%) and Sternocleidomastoideus (19.9±15.6%) activate after the FR-start. Hamstrings, Soleus, and L4-level Erectores Spinae (posterior muscles) activate after the FR-start in this order (11.4±16.8%, 17.7±16.6%, and 35.2±29.0%, respectively) and remain active until the movement end. The analysis of the kinematic strategies adopted by subjects revealed an association between TA-activation patterns and two kinematic strategies (hip/mixed strategy), quantified by an increase (p<0.05) of TA-activity duration in subjects adopting the hip strategy (89.9±34.5) vs. subjects adopting the mixed strategy (27.0±16.8). This suggests that TA sEMG activity could be able to discriminate among kinematic strategies, providing different information on balance control. Thus, the present analysis represents the first attempt to quantify the sEMG activity during FR-test in elderly subjects, providing an early contribution in building a reference frame for balance assessment in clinical context.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/230167 Collegamento a IRIS

2016 Heart Rate-Dependent Hysteresis of T-Wave Alternans in Primary Prevention ICD Patients
ANNALS OF NONINVASIVE ELECTROCARDIOLOGY
Autore/i: BURATTINI, LAURA; Man, Sumche; FIORETTI, Sandro; DI NARDO, Francesco; Swenne, Cees A.
Classificazione: 1 Contributo su Rivista
Abstract: Background: T-wave alternans (TWA) is usually performed at accelerated heart rates (HR) during exercise, while recovery TWA is typically not analyzed. Consequently, it is still unknown if TWA shows a HR-dependent hysteresis or not. Thus, the aim of the present study was to investigate TWA dependency on HR during both the exercise and recovery phases of an ergometer test, and to evaluate if recovery TWA may contribute to identify subjects at increased risk of arrhythmic events. Methods: Our HR adaptive match filter was used to identify TWA from electrocardiographic recordings acquired during a bicycle ergometer test in 266 patients with implanted cardio-defibrillator. During the 4-year follow-up, 76 patients developed tachycardia or ventricular fibrillation (ICD_Cases) and 190 did not (ICD_Controls). Results: TWA was statistically lower during exercise than recovery for HRs between 75 and 110 bpm (16-21 μV vs 20-27 μV; P < 0.05), and reverse for HRs between 120 and 130 bpm (41-51 μV vs 28 μV; P < 0.05). ICD_Cases and ICD_Controls showed significantly different TWA at 80 bpm (20 μV vs 15 μV; P < 0.05) and 140 bpm (15 μV vs 22 μV; P < 0.05) during exercise, and at 90 bpm (38 μV vs 21 μV; P < 0.05) and 95 bpm (33-24 μV vs 28 μV; P < 0.05) during recovery. Conclusions: TWA shows a HR-dependent hysteresis and there is a different behavior of TWA in ICD_Cases and ICD_Controls groups. Consequently, beside exercise TWA also recovery TWA may contribute to identify subjects at increased risk of arrhythmic events.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236053 Collegamento a IRIS

2016 T-Wave Alternans Hysteresis on Heart Rate
Computing in Cardiology 2015
Autore/i: BURATTINI, LAURA; Sumche, Man; FIORETTI, Sandro; DI NARDO, Francesco; Cees A, Swenne
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Microvolt T-wave alternans (TWA) increases with heart rate (HR). Thus, TWA is usually analyzed during exercise. However, since TWA during recovery is usually not analyzed, it is not clear if TWA and HR are linked by a one-to-one correspondence, or if it does exist a TWA hysteresis on HR. To investigate such issue TWA was identified in ECG recordings of 266 patients with implanted cardio-defibrillator acquired during a bicycle ergometer test, which included a HR-increasing exercise and a HR-decreasing recovery, both characterized by a HR from 80 to 125 bpm. TWA was always found to have a positive association with HR but, at each HR, exercise TWA was typically different from recovery TWA. Specifically, TWA increased exponentially during exercise (fitting-exponential-curve correlation: ρ=0.99, P<10-7) while decreased linearly during recovery (fittingline correlation: ρ=0.94, P<10-4). The two fitting curves crossed at about 115 bpm, so that for lower HRs (80-110 bpm) exercise TWA was significantly lower than recovery TWA (16-21 µV vs. 22-27 µV; P<0.01), while for higher HRs (120-125 bpm) exercise TWA was significantly higher than recovery TWA (41-51µV vs. 28 µV; P<10-6). Thus, it does exist a TWA hysteresis on HR since TWA does not depend only on the actual value of HR but also on such value being reached during exercise or recovery.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236095 Collegamento a IRIS

2016 Robustness of the Segmented-Beat Modulation Method to Noise
Computing in Cardiology 2015
Autore/i: AGOSTINELLI, ANGELA; GIULIANI, CORRADO; FIORETTI, Sandro; DI NARDO, Francesco; BURATTINI, LAURA
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Typically, ECG is corrupted by baseline wander (BW), electrode motion artifact (EM) and muscular artifact (MA). To eliminate them, ECG is usually pre-filtered by application of linear techniques which, however, do not remove in-band components which may limit the ECG clinical usefulness if further processing is not performed. The Segmented-Beat Modulation Method (SBMM) is a template-based filtering technique which segments each cardiac beat into QRS and TUP segments, respectively independent and proportional to heart-rate, and adaptively adjusts each reconstructed beat to its original length by modulating and demodulating the TUP segments. The aim of the present study was to evaluate SBMM robustness to noise by applying it to one synthetic and 18 clinical ECG tracings before and after corruption with BW, EM and MA. Results indicate that, in all cases, clean ECGs are estimated with errors <0.15 mV, typically greater in the QRS than in the TUP segments (0123 µV µV vs 0-25 µV; P<10-5). Moreover, MA little affected ECG estimation, while BW and EM caused higher errors especially in the QRS segment which however remained quite small. Thus, the SBMM resulted to be a filtering technique quite robust to noise.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236094 Collegamento a IRIS

2016 On the Heart-Rate Signal Provided by the Zephyr BioHarness 3.0
Proceeding of the 8th International workshop on Biosignal Interpretation
Autore/i: Nepi, D.; AGOSTINELLI, ANGELA; MARANESI, ELVIRA; SBROLLINI, AGNESE; MORETTINI, MICAELA; DI NARDO, Francesco; FIORETTI, Sandro; BURATTINI, LAURA
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The BioHarness 3 system (BH3) by Zephyr is a wearable cardiac sensor specifically designed for training optimization of professional athletes. BH3 records the electrocardiogram (BH3_ECG) and the heart-rate signal (BH3_HRS). Specifically, BH3_HRS is neither the popular tachogram nor the direct not-uniformly sampled heart-rate sequence as function of time. Consequently, the aim of the present study is to gain more insights on BH3_HRS that, if found reliable, would allow a future evaluation of the possibility of a clinical use of the sensor for cardiac risk evaluation. Data were acquired from an amateur athlete (male, 25 years old) during a 5-min rest followed by a 10 min exercise. R-peak detection was performed on BH3_ECG, and the obtained heart-rate signal (HRS) was low-pass filtered using the following six filters: 3-, 4-, and 5-sample averages and 0.30 Hz, 0.35 Hz, and 0.40 Hz 6th order Butterworth low-pass filters. The filtered HRSs were then compared to BH3_HRS in terms of correlation coefficient (ρ), mean square error (MSE), resting heart-rate variability (HRV) and exercise maximum heart rate. Results indicate that the HRS closest to BH3_HRS was obtained with the 3-point average (ρ=0.9688-0.9991, MSE=0.45-0.47 mV2; comparable resting HRV and exercise maximum heart rate).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247675 Collegamento a IRIS

2016 A method for computing the Functional Ambulation Profile score by stereophotogrammetric data
Lecture Notes in Electrical Engineering
Autore/i: Maranesi, E; Petrini, M.; Ghetti, G.G.; Mercante, O.; Barone, V.; Burattini, L.; Di Nardo, F.; Fioretti, S.
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Abstract: The Functional Ambulation Profile (FAP) Score is a performance index based on the assessment of selected time and distance parameters, during standard gait test. FAP is considered a reliable global parameter for gait evaluation. The first and original FAP score is provided in an automatic way by the GAITRite System, a portable electronic mat embedded with pressure-activated sensors. The present study was designed to achieve a FAP score computation which could be independent from its native environment, and could be implemented by means of classic gait analysis systems, as stereophotogrammetry. This goal was pursued computing the parameters, which FAP definition is based on, by means of processing of stereophotogrammetric data. The reliability of FAP computation was tested by direct comparison with the original GAITRite FAP score, in a single subject, during different walking trials (comfortable gait, very slow gait; very fast gait) and simulating several pathological gaits (gait with small step; “foot-drop” gait; “festinating” gait; “spastic” gait). No relevant differences detected between stereophotogrammetry-based and GAITRitebased estimates indicate that the proposed method is able to provide a reliable assessment of FAP in different kind of natural/pathological walking. The capability of FAP index to identify alterations of walking is also preserved. In conclusion, this study proposes the stereophotogrammetry-based computation of FAP as a valid alternative to the original GAITRite FAP. The convenience of an easy integration with classic stereophotogrammetry-based gait analysis parameters, supports the usefulness of stereophotogrammetry-based FAP in providing a complete picture of subject walking, without needing a further measurement system.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240335 Collegamento a IRIS

2016 Webcam and smartphone for the measure of spatial-temporal parameters of gait for treadmill use
Lecture Notes in Electrical Engineering
Autore/i: Barone, Vinicio; Verdini, F.; Di Nardo, F.; Maranesi, E.; Burattini, L.; Fioretti, S.
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Abstract: First author search in Pubmed(opens in a new window)|View at Publisher| Export | Download | Add to List | More... Lecture Notes in Electrical Engineering Volume 392, 2016, Pages 261-272 International Workshop on Mobile Networks for Biometric Data Analysis, 2014; Ancona; Italy; 30 October 2014 through 31 October 2014; Code 179299 Webcam and smartphone for the measure of spatial-temporal parameters of gait for treadmill use (Conference Paper) Barone, V. , Verdini, F., Di Nardo, F., Maranesi, E., Burattini, L., Fioretti, S. Università Politecnica delle Marche, Ancona, Italy View references (16) Abstract A very low cost prototype has been developed for the spatial and temporal analysis of human movement using an integrated system of last generation smartphones and a high-definition webcam, controlled by a laptop. The system can be used to analyse mainly planar motions in non-structured environments. In this paper, the accelerometer signal captured by the 3D sensor embedded in one smartphone, and the position of coloured markers extracted from the analysis of the webcam frames, are used for the computation of spatial-temporal parameters of gait. The system has been tested on a treadmill at different gait speeds. Accuracy of results is compared with that obtainable by a gold-standard stereometric instrumentation. The system is characterised by a very low cost and a very high level of automation. It has been thought to be used by non-expert users in ambulatory settings.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240336 Collegamento a IRIS

2016 The wireless surface electromyographic technique for supporting the assessment of fall risk in diabetic neuropathic patients
Lecture Notes in Electrical Engineering
Autore/i: Maranesi, E; Fioretti, S.; Barone, V.; Ghetti, G.G.; Mercante, O.; Rabin, R.A.; Burattini, L.; Di Nardo, F.
Editore: Springer Verlag
Classificazione: 2 Contributo in Volume
Abstract: The Functional Reach (FR) Test is commonly used in the clinical practice to identify elderly subjects at risk of recurrent falls. This study was designed to provide a useful tool for supporting the assessment of fall risk in diabetic neuropathic (DN) subjects: a non-invasive analysis of muscle activation patterns involved in the FR test using wireless surface electromyography (sEMG). Kinematic analysis was also performed to support results achieved by sEMG technique. A population of diabetic non-neuropathic subjects was considered as control group (CTRL). Kinematics was acquired by a 6-camera Elite optoelectronic system and passive markers were placed according to Davis protocol, with an additional marker placed on dominant wrist. sEMG analysis of Sternocleidomastoideus, Rectus Abdominis, Erectores Spinae at L4 level (L4), Rectus Femoris, Hamstrings (Ham), Tibialis Anterior (TA) and Soleus (Sol) was performed. No significant differences (p-value for evaluation of statistical significance was <0.05) were detected between groups in the computed kinematics parameters. sEMG analysis shows that in CTRL subjects, TA was identified as the first motor, since it activates before the start of FR movement; its action can be attributed to the anticipatory muscular activity necessary to initiate the body forward displacement. Sol and Ham, followed by L4, act mainly as tonic muscles, opposing the movement and preventing falls. Compared to CTRL group, DN subjects show an anticipatory recruitment of TA. The earlier activation of TA in DN group suggests that this anticipation could be a predictor of a greater propensity of the DN subjects to fall compared to non-neuropathic diabetic subjects.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/240337 Collegamento a IRIS

2016 Logistic Regression to Enhance Risk Assessment by Left Ventricular Ejection Fraction and f99
Computing in Cardiology 2015
Autore/i: GIULIANI, CORRADO; Swenne, Cees A; Man, Sumche; FIORETTI, Sandro; DI NARDO, Francesco; BURATTINI, LAURA
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Sudden cardiac death remains one of the leading causes of death in developed countries. Left ventricular ejection fraction (LVEF) and f99 are two noninvasive indexes of cardiovascular risk (traditional the former and innovative the latter) which, taken singularly, have not shown sufficiently high SCD predictive power to justify preventive actions. Thus, the aim of the present study was to investigate if their combination improves predictability of ventricular arrhythmias. To this aim, ECG recordings from 266 ICD patients, of which 76 developed ventricular tachycardia or fibrillation during the 4-year follow-up (ICD_Cases), and 190 did not (ICD_Controls). The ECGs of each patient was used to compute the f99, a repolarization index defined as the frequency at which the cumulative power energy reaches 99%. Eventually, a logistic regression between LVEF and f99 was performed in order to derive a combined predictor (CP) of ventricular arrhythmia. Goodness of each index was evaluated in terms of the area under the receiver operator curve (AUC). When used singularly, LVEF and f99 respectively provided an AUC of 0.67 and 0.64. When combined to get CP=-0.15-0.05·LVEF+0.03·f99, this provided an AUC of 0.71. In conclusion, use of logistic regression improves LVEF and f99 predictability of ventricular arrhythmias.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236093 Collegamento a IRIS

2016 A MATLAB-based graphical user interface for the identification of muscular activations from surface electromyography signals
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Mengarelli, Alessandro; Cardarelli, Stefano; Verdini, Federica; Burattini, Laura; Fioretti, Sandro; Di Nardo, Francesco
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In this paper a graphical user interface (GUI) built in MATLAB® environment is presented. This interactive tool has been developed for the analysis of superficial electromyography (sEMG) signals and in particular for the assessment of the muscle activation time intervals. After the signal import, the tool performs a first analysis in a totally user independent way, providing a reliable computation of the muscular activation sequences. Furthermore, the user has the opportunity to modify each parameter of the on/off identification algorithm implemented in the presented tool. The presence of an user-friendly GUI allows the immediate evaluation of the effects that the modification of every single parameter has on the activation intervals recognition, through the real-time updating and visualization of the muscular activation/deactivation sequences. The possibility to accept the initial signal analysis or to modify the on/off identification with respect to each considered signal, with a real-time visual feedback, makes this GUI-based tool a valuable instrument in clinical, research applications and also in an educational perspective.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/245155 Collegamento a IRIS

2016 Estimation of second-phase insulin secretion in the Zucker fatty rat
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: MORETTINI, MICAELA; DI NARDO, Francesco; Cogo, Carla E.; Faelli, Emanuela; FIORETTI, Sandro; BURATTINI, LAURA; Ruggeri, Piero
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The purpose of the present study was to test the efficacy of the empiric index SPIR (Second-phase Insulin Release) in the quantification of second-phase insulin secretion in the Zucker Fatty Rat. SPIR index is defined as the area under the curve of insulin between 8 and 90 min after an Intravenous Glucose Tolerance Test (IVGTT). The validation of such index was performed against the second-phase β-cell responsiveness index (Φ2) provided by C-peptide minimal model. To this aim, Φ2 and SPIR were simultaneously computed from IVGTT data, measured in six Zucker fatty rats (ZFR), 7-to-9week-old, and seven age-matched Zucker lean rats (ZLR). SPIR index showed a significant linear correlation with Φ2 (Pearson's correlation coefficient, r = 0.91, R-square = 0.82, P<0.001). Moreover, both Φ2 (P<0.001) and SPIR (P<0.001) showed a significant increase, in the ZFRs, compared to control group (ZLR). These findings suggest that the SPIR index is able to provide similar information of Φ2, in the evaluation of the second-phase insulin secretion and of its alteration in Zucker Fatty Rats. Thus, the study proposes the SPIR, as a suitable index for a simple, reliable and low-cost quantification of the second-phase insulin secretion in ZFR.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/245028 Collegamento a IRIS

2016 Frequency-of-occurrence of myoelectric patterns to evaluate gait motor control strategies after hip replacement surgery
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Agostini, Valentina; Di Nardo, Francesco; Fioretti, Sandro; Burattini, Laura; Rosati, Samanta; Balestra, Gabriella; Knaflitz, Marco
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Gait alterations are observed even years after hip replacement surgery. Such long-lasting alterations may arise from a global change of the motor control strategies. The aim of this work is to investigate the changes in gait motor control strategies of patients after hip replacement surgery by analyzing the frequency of occurrence (OF) of myoelectric activation patterns. We studied five lower limb muscles during gait, in hip prosthesis patients and controls. We found that patients adopt a motor control strategy that tends to prefer 'simplified' myoelectric patterns, showing a smaller number of activations within the gait cycle. This altered motor control was present both on the prosthesis and the sound side, and did not improve during the 12-month follow-up. The reduced number of activations is even more evident in lateral hamstrings and gluteus medius, which are the muscles more affected by hip replacement surgery. Furthermore, this study demonstrated that the OF is a sensitive parameter able to discover subtle changes in motor control strategies. Its use can be extended to other studies involving motor coordination, motor learning and motor control adaptations.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/245157 Collegamento a IRIS

2016 Dynamic knee muscle co-contraction quantified during walking
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Autore/i: Strazza, Annachiara; Mengarelli, Alessandro; Agostini, Valentina; Knaflitz, Marco; Burattini, Laura; Fioretti, Sandro; Di Nardo, Francesco
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The purpose of the present study was the quantification of the co-activation patterns of the knee extensor and flexor muscles during walking at self-selected speed and cadence. To this aim, the Statistical Gait Analysis, a recent methodology providing a statistical characterization of gait, was performed on surface EMG signals from Vastus Lateralis (VL) and Medial Hamstrings (MH) in 14 healthy young adult subjects. Muscular co-contraction was assessed as the overlapping period between activation intervals of agonist and antagonist muscles. Superimpositions between VL and MH activity were detected from terminal swing to the following loading response in 100% of the considered strides. This superimposition could be intended as an actual co-contraction of VL and MH, working across the same joint, the knee. It occurs in this gait phase likely in order to assist knee extension, developing muscle tension for weight acceptance during loading response, and to control knee flexion. A further less frequent (28.9±13.6% of the strides, P<0.001) superimposition was detected in terminal stance; this superimposition, however, should not be considered a real co-contraction, because VL and MH work on different joints. These findings have the merit to provide a novel data on the variability of the reciprocal role of VL and MH during walking, allowing a deeper insight in the physiological mechanisms that regulate the knee flexion/extension.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/245159 Collegamento a IRIS


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