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Mechanomyographic and electromyographic responses of the superficial quadriceps femoris muscles during fifty maximal isokinetic muscle actions at different velocities
The purpose of this investigation was to examine mechanomyographic (MMG) and electromyographic (EMG) responses of the superficial quadricep muscles during fatiguing isokinetic muscle actions of the dominant leg extensors. Ten adults (age 22 ± 2 years) volunteered to perform a test of 50, consecutive, maximal concentric muscle actions using a calibrated Cybex II dynamometer at one of three randomly selected contraction velocities (60, 180, and 300°·s−1) on three different days. Bipolar surface electrode arrangements were placed over the longitudinal axes of the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM). An MMG sensor was placed between the EMG electrodes on each muscle. The EMG and MMG amplitude values (root mean square, rms), as well as the peak torque (PT) were calculated for the 50 muscle actions, normalized to each respective maximal value then averaged across all subjects for each of the three tests. Polynomial regression analyses indicated that torque demonstrated a quadratic relationship (p < 0.05) across the 50 repetitions at 60°·s −1 and cubic relationships (p < 0.05) at 180 and 300°·s −1. The normalized EMG amplitude demonstrated cubic relationships (p < 0.05) for each muscle at each velocity. The normalized MMG amplitude decreased quadratically (p < 0.05) at 60 and 180°·s−1 for the VL and at all three velocities for the VM. The normalized MMG amplitude decreased linearly (p < 0.05) at 180°·s −1 for the VL and at all three velocities for the RF. These findings indicated dissociation between the EMG and MMG responses during fatiguing, dynamic muscle actions, with MMG amplitude more closely tracking torque production across the 50 repetitions. Differences were also found in MMG amplitude responses between the velocities tested as well as between the superficial muscles of the quadriceps femoris at each velocity. The response of the MMG signal during the fatiguing muscle actions could have been influenced by the proportion of type I and type II muscles fibers in each of the muscles examined, muscle fluid changes, and/or the influence of “muscle wisdom.” ^
Health Sciences, Recreation
Perry, Sharon R, "Mechanomyographic and electromyographic responses of the superficial quadriceps femoris muscles during fifty maximal isokinetic muscle actions at different velocities" (2001). ETD collection for University of Nebraska - Lincoln. AAI3004620.