The kinetics of recovery from neuromuscular fatigue resulting from exercise time trials (TTs) of different durations are not well-known.The aim of this study was to determine if TTs of three different durations would result in different short-term recovery in maximal voluntary contraction (MVC) and evoked peak forces.Twelve trained subjects performed repetitive concentric right knee extensions on an isokinetic dynamometer self-paced to last 3, 10, and 40 min (TTs).
Neuromuscular function was assessed immediately (<2 s) and 1, 2, 4, and 8 min after completion of each TT using MVCs and electrical stimulation.Electrical stimulations consisted of battery-powered generators single stimulus (SS), paired stimuli at 10 Hz (PS10), and paired stimuli at 100 Hz (PS100).Electrically evoked forces including the ratio of low- to high-frequency doublets were similar between trials at exercise cessation but subsequently increased more Hand Wash (P < 0.
05) after the 3 min TT compared with either the 10 or 40 min TT when measured at 1 or 2 min of recovery.MVC force was not different between trials.The results demonstrate that recovery of peripheral fatigue including low-frequency fatigue depends on the duration and intensity of the preceding self-paced exercise.
These differences in recovery probably indicate differences in the mechanisms of fatigue for these different TTs.Because recovery is faster after a 3 min TT than a 40 min TT, delayed assessment of fatigue will detect a difference in peripheral fatigue between trials that was not present at exercise cessation.