Effects of variable fatigue levels on reaction-time components

The effects of varying fatigue levels on reaction-time components were determined for 20 young, adult males. Each subject squeezed a hand-gripping device until strength decrements of 20, 40, or 60% were recorded; then the subject released his tension and then reacted to an auditory stimulus by gripping as quickly and forcefully as possible. Testing was also conducted under a nonfatigued state, and every subject was tested under all conditions. Total reaction time was divided into (a) a promoter component, the time from the stimulus to an alteration in the EMG of the finger flexors, and (b) a motor component, the time from the change in the EMG to the first sign of tension uptake. Analyses of variance failed to reveal any alterations in either reaction time or promoter time; however, there was a significant (p < .05) elongation of motor time when the muscle was fatigued, with motor time tending to increase linearly as fatigue increased. The results suggest that localized fatigue of this nature is primarily of peripheral (muscular) origin.