The goal of a study was to ascertain whether exercise time trials (TTs) of three different durations could render dissimilar time to short-term recovery from neuromuscular fatigue.

This study included 12 trained subjects who used an isokinetic dynamometer to perform repetitive concentric right knee extensions. The TTs were for 3, 10, and 40 mins. Neuromuscular function was assessed. Electrical stimulations comprised – single stimulus (SS), paired stimuli at 10 Hz (PS10), and paired stimuli at 100 Hz (PS100).

The findings showed that electrically evoked forces were comparable between TTs at exercise cessation. However, they rose higher after the 3 min TT than with the other TTs assessed – when measured at 1-2 min after recovery. Additionally, the maximal voluntary contraction (MVC) force was not different between trials. 

Hence, recovery of peripheral fatigue (including low-frequency fatigue) varies with the duration and intensity of the self-paced exercise that caused it. These differences in recovery suggest differential mechanisms of fatigue due to different TTs. Owing to the quick recovery after a 3 min TT than a 40 min TT, delayed assessment of fatigue can render a variable assessment of peripheral fatigue – when not initiated at exercise cessation.

Source: Frontiers in Physiology. 2020; 11: 399. Published online 2020 May 14. doi: 10.3389/fphys.2020.00399