Time and Frequency Domain Analyses of the Surface Mechanomyogram During Submaximal to Maximal Isokinetic Muscle Actions of the Biceps Brachii

Abstract

2346 PURPOSE: The purpose of this study was to examine the mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus torque relationships during isokinetic muscle actions of the biceps brachii. METHODS: Ten adults (mean ± SD age = 21.6 ± 1.7 yrs) performed submaximal to maximal isokinetic muscle actions of the dominant forearm flexors at a velocity of 30°·s−1 on a calibrated Cybex II dynamometer. Following determination of isokinetic peak torque (PT), the subjects randomly performed submaximal step muscle actions in 10% increments from 10% to 90% PT. RESULTS: Polynomial regression analyses indicated that MMG amplitude increased linearly (r2 = 0.982), while MMG MPF was best fit with a cubic (R2 = 0.786) model with increases in isokinetic torque from 10% to 100% PT. There were no significant mean differences, however, in MMG MPF from 10% to 100% PT. CONCLUSION: The linear increase in MMG amplitude and relatively stable MMG MPF with increases in isokinetic torque to 100% PT may indicate that recruitment of additional motor units, with little change in the global motor unit firing rate, is the primary motor control strategy for increasing torque production during dynamic muscle actions of the biceps brachii.