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Table 7 Overview of studies of force and MMG

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 the effect of temperature on MMG and the force response
[69] EMG: Ag–AgCl (diameter = 8 mm, inter-electrode distance = 35 mm); MMG: microphone sensor (Daia Medical, Tokyo, Japan; diameter = 10 mm, mass = 5 g); Force: (model LU-00KSB34D, Kyowa, Tokyo, Japan) SOL and MG 8 healthy male subjects, age (means ± SEs) 23.3 ± 0.5 years, height 173.6 ± 2.7 cm, body mass 71.1 ± 4.6 kg At temperatures of 34, 15, 20 and 25 °C, a 10-Hz stimulation for 8 s with a 30-s rest between trials was delivered Under cooling conditions, the CT and ½Tr increased, and the maximum peak force development (\(dF/dt\)) and relaxation (\(RdF/dt\)) decreased; in addition, a low RMS of the force fluctuations and low MG and SOL MMG amplitudes were obtained
Remark: MMG can be used to study the muscle contractile properties under a wide range of physiological conditions
Study 2: analysis of the effect of changes in contractile and viscoelastic properties due to EMD
[67] MMG: accelerometer (model ADXL202JE, Analogue Devices, Norwood, MA, USA); EMG: four silver bar electrodes; Force: (model SM-200 N, Interface, UK; operation range = 0 and 200 N) MG 16 healthy male subjects, age 24 years, body mass 75 ± 2 kg, stature 179 ± 2 cm A supramaximal stimulation followed by a rest time of 10 min was delivered while the ankle was positioned at 20°. Before and after stretching, a set of three tetanic stimulations was delivered and followed by 15 min to 2 h s of rest During recovery, the delay between EMG-MMG returned to pre-stretching values within 900 s, and Δt MMG-F remain lengthened for 7200 s
Remark: significant lengthening of the EMD was observed, possibly due to changes in the MTU stiffness
Future works:
1. The involvement of parallel and series elastic components in the lengthening of ∆t MMG-F after stretching should be examined
2. The sites and duration of the MTU deformation after stretching should be analyzed
3. The release of \({Ca}^{2+}\) and the involvement of sensitivity in the stretching-induced changes in excitation–contraction coupling should be investigated
Study 3: analysis of the use of MMG, EMG and force approaches to evaluate the time course of stretching-induced changes in mechanical and viscoelastic properties of MTUs
[68] MMG: mono-directional accelerometer (model ADXL202JE, Analogue Devices, Norwood, MA, USA); EMG: three Ag–AgCl electrodes MG 11 healthy male subjects, age (means ± SDs) 22 ± 1 years, body mass 77 ± 5 kg, stature 1.78 ± 0.05 m Stimulation with an amplitude of 10–100 mA, a pulse duration of 307 µA, and lasting for 5 s to 1 min at 50 Hz was followed by 110% supramaximal stimulation and rest for 600 s. A tetanic stimulation was delivered every 5 s for 15 min and followed by 2 h of rest The MMG-RMS recovered to the pre-stretching values, and the MMG-PP and \({P}^{F}\) values remained low. No difference in the EMG response was found between the two experiments (p > 0.05)
Remark: no significant differences in the control parameters for the EMG, MMG and force features were found during the stimulation sets and during the 2-h recovery period
Future work: the rule of transverse MTUs based on the MMG amplitude should be studied
Study 4: analysis of the effects of the amplitudes in the force variation between force and local fatigue using biomechanics and physiological measures
[70] ES: Grass model S48; EMG: bipolar surface electrodes (Ag–AgCl electrodes, Ambu Blue Sensor N, Denmark); MMG: (Bruel and Kjaer 4507 ± 70 g) TB 15 healthy male subjects, age 24 ± 4 years, mean height 177.7 ± 4.9 cm, weight 75.8 ± 8.7 kg EMG, MMG, and blood flow velocity recordings of the triceps were collected at 2-min intervals during supramaximal fatiguing stimulation (20 and 100 Hz, pulse duration of 50 µs and train duration of 1 s) and at baseline. Test contraction at 15% of the force was exerted for 12 s Changes in mechanical action with or without rest delayed and reduced the rate of fatigue development compared with those observed under isometric, isotonic and sustained conditions
Remark: force variation at different amplitudes might yield slower fatigue responses under a set time course than those observed during sustained low-level contractions