Fig. 8.

Levels of force application in excess of this representative subject's aerobic peak (A and C), triggered a reliance on anaerobic metabolism for force production, and as a result, rates of EMG activity increased (ΔAEMG/Δtime). At lesser levels of force application, these measures were essentially constant throughout the exercise bout. B and D: rates of AEMG increase from the 123 exhaustive bouts of knee extension administered in this study. Measured forces (A and C), and study means of the forces ± SE (B and D) eliciting the aerobic peaks are illustrated by the vertical lines in each panel (blue = 0.6 duty cycle, red = 0.3 duty cycle).