The influence of electromyographic recording methods and the innervation zone on the mean power frequency–torque relationships

Abstract

This study examined the effects of electromyographic (EMG) recording methods and innervation zone (IZ) on the mean power frequency (MPF)–torque relationships. Nine subjects performed isometric ramp muscle actions of the leg extensors from 5% to 100% of maximal voluntary contraction with an eight channel linear electrode array over the IZ of the vastus lateralis. The slopes were calculated from the log-transformed monopolar and bipolar EMG MPF–torque relationships for each channel and subject and 95% confidence intervals (CI) were constructed around the slopes for each relationship and the composite of the slopes. Twenty-two to 55% of the subjects exhibited 95% CIs that did not include a slope of zero for the monopolar EMG MPF–torque relationships while 25–75% of the subjects exhibited 95% CIs that did not include a slope of zero for the bipolar EMG MPF–torque relationships. The composite of the slopes from the EMG MPF–torque relationships were not significantly different from zero for any method or channel, however, the method and IZ location slightly influenced the number of significant slopes on a subject-by-subject basis. The log-transform model indicated that EMG MPF–torque patterns were nonlinear regardless of recording method or distance from the IZ.