Exercise-induced muscle damage, repair, and adaptation in old and young subjects.

This study examined exercise-induced muscle damage, repair, and adaptation in 10 college age women and 10 women over age 60. On two sessions spaced 7 days apart, subjects performed an eccentric exercise of the forearm flexors consisting of 24 muscle actions at an intensity of 115% of isometric strength. Serum creatine kinase activity, flexed and relaxed elbow joint angles, and muscle pain were assessed prior to and for 5 days after each exercise session. The exercise resulted in similar changes in CK, muscle pain, and inability to fully flex the forearm for old and young subjects. The old group demonstrated greater muscle shortening (a decrease in the relaxed elbow joint angle). The old and young groups adapted to the first exercise such that changes in all criterion measures were reduced following the second exercise. For the physically active subjects in this study, the damage process (with the exception of muscle shortening) takes a similar course for old and young. The repair process is equally as effective in old and young, and older subjects show the same ability to adapt to the damage as young subjects.