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Table 6 Use of MMG for studying endurance and fatigue

From: Assessment of muscle activity using electrical stimulation and mechanomyography: a systematic review

Authors Sensor and electrode type Electrode site Dataset Methodology Results and discussion
Study 1: analysis of torque and MMG fluctuations at various joint angles
[63] Triaxal accelerometer-based MMG sensor (WAX3, Axivity, Newcastle upon Tyne, UK) Erector spinae of the forearm and wrist flexors 5 male and 3 female subjects, age 22.9 ± 2 years, height 1.8 ± 0.1 m, weight 69.8 ± 14.9 kg Pulses of 25 to 35 mA at pulse durations/intervals of 200/50 µs were delivered, and the muscle twitch contraction was measured. The endurance protocol consisted of 2 Hz, 4 Hz, and 6 Hz (3 min each) with 5 s of no stimulation between each stage The EI values were reasonably reproducible, particularly those obtained with the 2- and 4-Hz stimulations
Remark: in young healthy individuals, the erector spinae muscle has a lower endurance index than the leg muscles
Future work: the experiment was conducted on young healthy subjects; thus, the application of the system for evaluating lower back pain in the healthy population should be investigated
Study 2: analysis of the effect of exercise on endurance
[62] Accelerometer-based MMG sensor GM 56-year-old female with muscle sclerosis A 3-min, 2-, 4- and 6-Hz stimulation signal was applied, and the endurance index was determined as the percentage of the acceleration at the last stage of the stimulation frequency relative to the peak accelerometer records The walking endurance and oxidative capacity were improved
Future works:
1. The effect of voluntary exercises on muscle plasticity and the role of muscle oxidative capacity on assisting individuals with MS should be evaluated
2. The use of a large sample size for examining the role of muscle plasticity to improve the walking function in people with MS should be investigated
Study 3: evaluation of rider time and virtual distance in SCI
[64] ES: two self-adhesive surface electrodes (oval, 2″ × 4″); MMG: accelerometers (Entran EGAS, weight = 1 g, 2–150 Hz, gain of 25) VM, RF and VL 12 SCI subjects, mean age 37 years, height 1.8 m, mass 80.6 kg An electrical stimulation of 50 Hz for 500 µs was increased to a current of 140 mA to maintain a cadence of 32 RPM over 0.4 s and applied every 1.88 s An improved electrically activated cycling alternated the activity of synergistic muscles in SCI, and different RMS values of MMG signals were obtained from all the muscles
Remark: the MMG amplitude decreased due to muscle fatigue and the virtual distance, and both the stimulation and co-activation protocols yielded the same mechanical output
Future work: the use of improved stimulation techniques to evaluate improvements during a longer training practice without an external rider should be evaluated
Study 4: analysis of endurance and feelings of fatigue in FRDA
[65] MMG: tri-axial accelerometer (WAX-9; Axivity, UK); ES: electrodes (5.08 cm by 10.16 cm, Pro Advantage by NDC) Forearm flexor 10 healthy subjects, 16 FRDA subjects The forearm flexor muscles were stimulated with 3 min of ES at 2, 4, and 6 Hz with a 5-s rest between stages A correlation was found among the mitochondrial capacity, disease severity and muscle-specific endurance
Remark: people affected by FRDA exhibit lower forearm muscle endurance than ABs
Future work: MMG and NIRS measurement methods are correlated with disease severity, and this correlation should be further investigated