Electromyographic and mechanomyographic responses.

The purpose of the present study was to determine the electromyographic (EMG) and mechanomyographic (MMG) responses to cycle ergometry at critical power (CP). Seven moderately active males (25 +/- 3 years) completed a 60-min trial at their CP estimated from a nonlinear, 3 parameter regression model. EMG and MMG amplitudes were recorded from the vastus lateralis during 60-min continuous rides at CP. The mean CP was 175 +/- 25 W, which represented 56 +/- 5% of the subjects' peak power outputs. The results indicated that the slope coefficient for the EMG amplitude versus time relationship was not significantly different from zero; however, MMG amplitude decreased significantly over the 60 min. This dissociation between the electrical (EMG) and mechanical (MMG) aspects of muscular activity during cycle ergometry may be due to neuromuscular changes associated with "muscle wisdom" or changes in muscular compliance.