Neuromuscular changes and the rapid adaptation following a bout of damaging eccentric exercise

IntroductionAn initial bout of eccentric exercise is known to protect against muscle damage following a repeated bout of the same exercise; however, the neuromuscular adaptations owing to this phenomenon are unknown. AimTo determine whether neuromuscular disturbances are modulated following a repeated bout of eccentric exercise. MethodsFollowing eccentric exercise performed with the elbow flexors, we measured maximal voluntary force, resting twitch force, muscle soreness, creatine kinase (CK) and voluntary activation (VA) using motor point and motor cortex stimulation at baseline, immediately post-exercise and at 1, 2, 3, 4 and 7days post-exercise on two occasions, separated by 3weeks. ResultsSignificant muscle damage and fatigue were evident following the first exercise bout; maximal voluntary contraction (MVC) was reduced immediately by 35% and remained depressed at 7days post-exercise. Soreness and CK release peaked at 3 and 4days post-exercise respectively. Resting twitch force remained significantly reduced at 7days (-48%), whilst VA measured with motor point and motor cortex stimulation was reduced until 2 and 3days respectively. A repeated bout effect (RBE) was observed with attenuated soreness and CK release and a quicker recovery of MVC and resting twitch force. A similar decrement in VA was observed following both bouts; however, following the repeated bout there was a significantly smaller reduction in, and a faster recovery of, VA measured using motor cortical stimulation. ConclusionOur data suggest that the RBE may be explained, partly, by a modification in motor corticospinal drive.