Neuromuscular disturbance outlasts other symptoms of exercise-induced muscle damage

This study examined the biochemical, immunological, functional, and neuromuscular responses associated with exercise-induced muscle damage in the quadriceps of untrained men. Muscle damage and soreness was elicited with maximal concentric/eccentric muscle actions at 0.53 rads s(-1). Significant (P<0.05) soreness was evident 1, 2, and 3 days following muscle insult, while plasma creatine kinase, a marker of muscle damage, was elevated 3 and 5 days post-insult. Plasma interleukin-Ibeta was significantly increased within 5 min, and remained elevated 1, 2, 5, and 7 days post-insult. Maximal isometric quadriceps function was impaired (P<0. 05) for 5 days following muscle challenge. Maximal isokinetic performance at 1.09 rads s(-1) was diminished (P<0.05) for 2 days post-insult; no significant decrements at 3.14 rads s(-1) were noted. Average electrical activation (iEMG) of the quadriceps was unaltered, but iEMG activity of the rectus femoris - where soreness was focused - was significantly increased. Neuromuscular efficiency (torque/iEMG) was compromised throughout the 10-day post-insult period investigated. While other symptoms of exercise-induced muscle damage dissipate within 7 days, neuromuscular perturbation persists for at least 10 days.