Table 4.

Records on activity related to muscle physiology.

Authors	Sensor used	Subjects	Muscle activity assessed	Experimental protocol	Parameters	Results	Application / Limitation / Future work
63	Piezoelectric MMG membranes	Number of subjects not mentioned	Muscle vibration / muscle contractions	Sustained voluntary isometric contraction	Power difference, MMG and EMG amplitude	Power difference increased from 5% to 90% by rubbing skin.	The EMG and MMG probe used in experiment was not standardized and it was tested only on sustained muscle contraction.
64	Accelerometer	10 men	Isometric muscle contractions	Isometric muscle contractions at 10%, 20%, and 40% MVC	RMS and mean power spectral frequency (MPF)	Variation in RMS and MPF with variation in sensor location.	Effect of variation in MMG sensor location was studied only for voluntary contraction.
60	Displacement sensor	10 men	Muscle stiffness	Electrically evoked maximal single twitch	Tc, Dm	No significant change in the Tc and Dm of BB muscle was observed after bed rest.	Muscle stiffness assessment can be extended for voluntary contraction to have results closer to natural muscle condition
66	Hybrid EMG / MMG probe	15 women (9 with Parkinson disease, 6 healthy)	Muscle stiffness and ability to carry load	Submaximal load holding	MMG Amplitude and MDF	Higher RMS in agonist muscle and lower MDF in both agonist and antagonist muscles.	Lack of normalization for EMG data.
65	Hybrid EMG / MMG probe	20 women (10 with Parkinson’s disease, 10 healthy)	Tremor-related changes in Parkinson disease (PD) patients	Maximal isometric contraction	RMS, MDF for both PD patients and control subjects	No intergroup difference in the assessed parameters was observed due to the medication.	Maximal and submaximal load tasks were performed in different days which could alter the results of study
62	Piezoelectric transducer	20 (10 men, 10 women)	Isometric contractions	Muscle isometric ramp and step contractions	MMG MPF, MMG total intensity, first and second principal components	The MMG MPF and first principal component showed higher values in ramp contractions than in step contractions.	Spectral properties of EMG and MMG signals can also be observed for other muscles.
61	Piezoelectric transducer	12 (6 men, 6 women)	Contribution of BB to elbow flexion concentric / eccentric activity	Voluntary concentric and eccentric contractions at 20%, 40%, 60%, and 80% load	Elbow angle	The total intensity of MMG during eccentric contractions was higher than that obtained during concentric contractions.	Spectral properties of EMG and MMG signals can also be observed for other muscles and results may be compared to BB for generalization.
59	Laser measurement device	19 (gender not mentioned)	Exercise hypertrophy & disuse atrophy	Electrically evoked stimulation and then strength training by bicep curl to induce muscle hypertrophy	Dm, Tc, Vc	Dm and Vc showed a decline on the same time points while Tc remained stable throughout the hypertrophic and atrophic phases.	Using dominant limb as control may change the results of contractile properties, because motor unit activity has been observed to effect homologous contralateral limb.
58	Microphone	18 men	Change in neuromuscular efficiency and muscle stiffness after eccentric contractions	25 contractions at 50% MVC of elbow flexion	MMG RMS and MDF	MMG RMS decreased and the MMG MDF increased during the recovery period after contractions.	Future work can be done on different intensity levels for muscle stiffness assessment.
57	Piezoelectric accelerometer	10 men	Mechanical deformation of muscle	Resting and ramp contraction from 5% to 85% MVC	RMS correlation coefficient between the rest and contraction states, phase correlation coefficient	High similarity in bulk movement between resting and contracting muscle was observed.	Intensity variation in ramp contraction is not addressed in the study.