Analysis of crosstalk in Mechanomyographic signals from elbow flexors during forearm flexion, pronation and supination tasks

Muscle assessment has diverse applications including sports, athletics, medicine and prosthetic control. Mechanomyographic (MMG) signals have their significant importance for assessment of muscle function. Crosstalk is the contamination of MMG signals coming from target muscle by the signals coming from adjacent muscles. MMG signals do exhibit crosstalk, thus measurement of crosstalk is of vital significance in muscle function study. This research examined crosstalk, root mean square (RMS) and mean power frequency (MPF) for MMG signals from three elbow flexor muscles including biceps brachii (BB), brachialis (BRA) and brachioradialis (BRD). Three sustained isometric tasks including forearm flexion, pronation and supination were performed. Further this study analyzed crosstalk and MMG signal parameters in three different directions to muscle fiber axes, at five different submaximal to maximal torque levels, with variation in anthropometric parameters including skinfold thickness (ST), inter-sensor distance (ISD), length (LA) and circumference (CA) of arm. During each task, three microelectromechanical systems (MEMS)-based tri-axial accelerometers were used to obtain the MMG signals from the longitudinal, lateral and transverse directions with respect to muscle fibers. Peak cross-correlation coefficients at zero-time lags were used for quantification of the crosstalk. Crosstalk values showed statistical significance among all nine possible axes pairs (p<0.05, η2=0.160-0.510). The transverse axis showed lowest MMG RMS values and the transverse axes pair generated the lowest mean crosstalk values (2.160-9.140%). Submaximal to maximal (20%, 40%, 60%, 80% and 100% maximal voluntary contraction) torque levels were observed to have strong positive correlations with crosstalk values and MMG RMS (r>0.700) while strong negative correlations (r<-0.900) with MMG MPF. Negligible correlations were observed for crosstalk, MMG RMS and MMG MPF with the four anthropometric parameters. The results may be used to improve our understanding on mechanics of the elbow flexor muscles during sustained isometric forearm flexion, pronation and supination tasks using the MMG technique.