Muscle adaptation prior to recovery following eccentric exercise.

The effects of performing a second eccentric exercise bout prior to and after recovery from the first bout were compared. Twenty subjects performed 70 eccentric actions with the forearm flexors. Group A (n = 9) and group B (n = 11) repeated the same exercise 5 and 14 days after the initial bout, respectively. Dependent variables included muscle soreness, elbow joint angles, isometric strength, and serum creatine kinase (SCK). Subjects were tested pre-exercise and up to day 5 following each bout. The first bout produced significant changes in all measures for both groups (P less than 0.01). Values remained significantly different from baseline on day 5 when group A repeated the exercise (P less than 0.01) but were back to normal when group B performed bout 2. For both groups an adaptation occurred; significantly smaller changes in dependent variables were produced by the second bout, and recovery time was faster whether or not muscles were fully restored (P less than 0.01). The repeated bout did not exacerbate soreness, performance decrements, and elevation of SCK when performed by affected muscles that had not fully recovered from the first bout. Thus, the results suggest that an adaptation response had taken place prior to full recovery and restoration of muscle function following the initial eccentric exercise bout.