MUSCLE STRENGTH AND FIBER ADAPTATIONS TO A YEAR-LONG RESISTANCE TRAINING-PROGRAM IN ELDERLY MEN AND WOMEN

Background. To study the effects of resistance training on muscle stre ngth and size in older people, we enrolled 8 men and 17 women (mean ag e 68.2 +/- 1 SEM) into a one-year exercise trial. Methods. Subjects we re randomly assigned to exercise or control groups. Muscle biopsies we re obtained from 11 subjects (8 exercisers/3 controls) at baseline and after 15 weeks; exercisers underwent another biopsy at 30 weeks. Afte r testing maximum strength using the 1-RM method, the exercisers began a 12-exercise circuit (3 sets of 8 repetitions at 75% of 1-RM), 3 tim es a week. The controls repeated the strength testing every 15 weeks. They were asked to continue usual activities and not to start any exer cise program. Results. With exercise, muscle strength increased, avera ge increases ranging from 30% (hip extensors) to 97% (hip flexors). St rength increased rapidly over 3 months, then plateaued for the duratio n of the experiment. No strength changes were observed in sedentary co ntrols. Cross-sectional area of type 1 muscle fibers increased in exer cisers by 15 weeks (29.4 +/- 1%, p < .02) and after 30 weeks (58.5 +/- 13.7%, p < .002) compared to baseline. Type 2 fiber area did not chan ge at 15 weeks, but increased by 30 weeks of training (66.6 +/- 9.5%, p < .0002). Conclusions. These results suggest that prolonged moderate to high intensity resistance training may be carried out by healthy o lder adults with reasonable compliance, and that such training leads t o sustained increases in muscle strength. These improvements are rapid ly achieved and are accompanied by hypertrophy of both type 1 and type 2 muscle fibers.