Ultrastructural muscle damage in young vs. older men after high-volume, heavy-resistance strength training

This study assessed ultrastructural muscle damage in young (20-30 yr old) v s. older (65-75 yr old) men after heavy-resistance strength training (HRST) . Seven young and eight older subjects completed 9 wk of unilateral leg ext ension HRST. Five sets of 5-20 repetitions were performed 3 days/wk with va riable resistance designed to subject the muscle to near-maximal loads duri ng every repetition. Biopsies were taken from the vastus lateralis of both legs, and muscle damage was quantified via electron microscopy. Training re sulted in a 27% strength increase in both groups (P < 0.05). In biopsies be fore training in the trained leg and in all biopsies from untrained leg, 0- 3% of muscle fibers exhibited muscle damage in both groups (P = not signifi cant). After HRST, 7 and 6% of fibers in the trained leg exhibited damage i n the young and older men, respectively (P < 0.05, no significant group dif ferences). Myofibrillar damage was primarily focal, confined to one to two sarcomeres. Young and older men appear to exhibit similar levels of muscle damage at baseline and after chronic HRST.