Change in slope of conduction velocity linear regression as an indicator of muscle fatigue

The present study investigates the behavior of action potential conduction velocity (CV) on each repetition of three isokinetic test sets, focusing on the repetition of peak torque. Results are compared for linear regression slope among the isokinetic sets regarding the rest intervals of one and two minutes. The surface electromyographic signals were recorded from the vastus lateralis muscle during the exercises of maximal concentric repetitions of dominant knee extension at 60°/s. Results show that the slope of CV linear regression increases inside a repetition. However, when observed along the whole set, or between consecutive sets, the CV slope has a decreasing tendency which is higher for shorter rest intervals. This behavior suggests CV slope as good muscle fatigue indicator during isokinetic tests.