Validation of mDurance, A Wearable Surface Electromyography System for Muscle Activity Assessment

Abstract

The mDurance® system is an innovative digital tool that combines wearable surface electromyography (sEMG), mobile computing and cloud analysis to streamline and automatize the assessment of muscle activity. The tool is particularly devised to support clinicians and sport professionals in their daily routines, as an assessment tool in the prevention, monitoring rehabilitation and training field. This study aimed at determining the validity of the mDurance system for measuring muscle activity by comparing sEMG output with a reference sEMG system, the Delsys® system. Fifteen participants were tested during isokinetic knee extensions at three different speeds (60, 180, and 300 deg/s), for two muscles (rectus femoris [RF] and vastus lateralis [VL]) and two different electrodes locations (proximal and distal placement). The maximum voluntary isometric contraction was carried out for the normalization of the signal, followed by dynamic isokinetic knee extensions for each speed. The sEMG output for both systems was obtained from the raw sEMG signal following mDurance's processing and filtering. Mean, median, first quartile, third quartile and 90th percentile was calculated from the sEMG amplitude signals for each system. The results show an almost perfect ICC relationship for the VL (ICC > 0.81) and substantial to almost perfect for the RF (ICC > 0.762) for all variables and speeds. The Bland-Altman plots revealed heteroscedasticity of error for mean, quartile 3 and 90th percentile (60 and 300 deg/s) for RF and at mean and 90th percentile for VL (300 deg/s). In conclusion, the results indicate that the mDurance® sEMG system is a valid tool to measure muscle activity during dynamic contractions over a range of speeds. This innovative system provides more time for clinicians (e.g., interpretation patients' pathologies) and sport trainers (e.g., advising athletes), thanks to automatic processing and filtering of the raw sEMG signal and generation of muscle activity reports in real-time.

Post-COVID-19 Syndrome and the Potential Benefits of Exercise

“…New trends in resistance and cardiopulmonary training methods appeal to more individualized regimes with a variety of exercises, stimuli and intensities, which are controlled by incorporating new technologies and monitoring tools. Current training methods are based on new approaches to monitoring exercise intensity (e.g., rate of force development, movement velocity), technical execution (e.g., biomechanics, electromyography), readiness (e.g., heart rate variability) and physiological responses (e.g., ventilation, lactate, core temperature, heart rate, muscle oxygen saturation) while providing biofeedback in real time, ensuring the accomplishment of targeted results [125][126][127][128][129][130]. Likewise, a number of portable devices, wearable tools and apps for physical activity and fitness are emerging, making remote control of the patients' evolution possible [131].…”

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“…A superficial Electromyography (sEMG) will measure the neuromuscular activity over the RF and GM muscles and their activity during gait. This outcome will be collected with a sEMG device called mDurance [ 43 , 44 ]. The sEMG sensors will be placed in the motor point of the RF and GM muscles according to the recommendations of the SENIAM protocol [ 45 ].…”

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“…The reliable and validated surface electromyography (sEMG) mDurance ® system (mDurance Solutions SL, Granada, Spain) was used to record muscle activity during a functional task (ICC = 0.916; 95%CI = 0.831–0.958) [ 23 ]. The muscles assessed were the rectus femoris, vastus lateralis, and vastus medialis of the quadriceps.…”

“…The mDurance ® system (mDurance Solutions SL, Granada, Spain) consists of three parts: (a) a Shimmer3 EMG unit (Realtime Technologies Ltd., Dublin, Ireland), which is a bipolar surface electromyography sensor for the acquisition of muscle activity—each Shimmer3 has two channels, with a 1024 Hz sampling rate and applies an 8.4 Hz bandwidth, while the EMG signal resolution is 24 bits, with an overall amplification of 100–10,000 v / v [ 23 ]; (b) the mDurance Android application, which receives data from Shimmer3 and sends it to a cloud service [ 23 ]; (c) the mDurance cloud, service where data are stored, filtered and analyzed [ 23 ].…”

“…The raw data were processed and filtered using a fourth-order Butterworth bandpass filter with a 20–450 Hz cut-off frequency. The signal was smoothed using a window size of 0.025 s root mean square (RMS) and 0.0125 s overlap between windows [ 23 ]. The main variable recorded for muscle activity was the mean RMS, expressed in microV, of the middle third of the isometric contraction.…”