DELAYED RECOVERY OF KNEE EXTENSION TORQUE FOLLOWING MAXIMAL ECCENTRIC CONTRACTIONS MAY BE DUE TO CENTRAL FATIGUE

This study compared 1) The isometric strength, and 2) Peripheral and central fatigue assessed by resting twitch and voluntary activation, following maximal eccentric contractions of knee extensors in young men and women. Nine healthy participants performed 150 maximal eccentric contractions at 60 degls of the knee extensor muscles while on a dynamometer. Maximal voluntary isometric contractions (MVIC) were assessed before, immediately, 1 day, 2 days, and 14 days after the eccentric contractions. Electrical stimulation was applied over the skin of knee extensor muscles to elicit twitch torque responses during and immediately following each MVIC. The MVIC torque, rate of torque development (RTD), resting twitch torque (RT), voluntary activation (VA), and time to peak decreased from the baseline after the eccentric fatiguing contractions (P c 0.05). RT and time to peak increased and fully recovered after 1 day (P > 0.05; compared with baseline). However, MVIC, RTD, and VA increased during the recovery but did not fully recover after 14 days (P c 0.05; compared with baseline). These results suggest that the delayed recovery of toque production is mainly due to decrements in central nervous system