Acute (0-2h) and delayed (2-8D) effects of exercise-induced muscle damage and soreness on elbow target movements

The aim was to examine the acute and delayed effects of exercise-induced muscle damage and soreness on elbow target movements (TM) performance and control. Ten males performed an exercise of 50 maximal eccentric elbow actions. TMs were performed at three movement ranges. Maximal forces, active stretch reflex and TM were tested, and muscle soreness, creatine kinase and elbow joint stiffness were determined acute (after and 2 h) and delayed (2, 4, 6, 8d) postexercise. Both the long lasting muscle soreness and force drop were observed after the exercise. Joint stiffness was increased at 2 h postexercise. The highest deterioration in flexion-TM performance was found at the time (2 h) and at the elbow angles (most flexed) where force drop was the greatest. The increased TM time was concomitant with the flexors changed timing, decreased peak EMG, and with their reduced stretch reflex amplitude. However, the effects on triphasic EMG activity pattern of TM were not joint angle specific. Dysfunction of fastest motor units and the sensitization of small group III / IV muscle afferents might have been responsible for the amplitude modulations of the activity pattern.