Effects of fatiguing isometric and isotonic exercise on resisted and unresisted reaction time components.

Fractionated resisted and unresisted RT for a knee-extension task was assessed on 12 male subjects over a 10-day treatment period. The first 4 days were baseline days and were designed to stabilize all RT values as well as strength measures. For the next 6 days the subjects were alternately administered isometric and isotonic exercise designed to fatigue the quadriceps musculature. Although significant strength decrements were manifested for both isometric exercise (57%) and isotonic exercise (35%), no changes were shown in the unresisted fractionated RT components. Conversely all resisted RT changes were manifested in the muscular component suggesting a peripheral site for neuromuscular fatigue.