SKELETAL-MUSCLE ADAPTATIONS DURING EARLY PHASE OF HEAVY-RESISTANCE TRAINING IN MEN AND WOMEN

An 8-wk progressive resistance training program for the lower extremit y was performed twice a week to investigate the time course for skelet al muscle adaptations in men and women. Maximal dynamic strength was t ested biweekly. Muscle biopsies were extracted at the beginning and ev ery 2 wk of the study from resistance-trained and from nontrained (con trol) subjects. The muscle samples were analyzed for fiber type compos ition, cross-sectional area, and myosin heavy chain content. In additi on, fasting blood samples were measured for resting serum levels of te stosterone, coristol, and growth hormone. With the exception of the le g press for women (after 2 wk of training) and leg extension for men ( after 6 wk of training), absolute and relative maximal dynamic stength was significantly increased after 4 wk of training for all three exer cises (squat, leg press, and leg extension) in both sexes. Resistance training also caused a significant decrease in the percentage of type IIb fibers after 2 wk in women and 4 wk in men, an increase in the res ting levels of serum testosterone after 4 wk in men, and a decrease in cortisol after 6 wk in men. No significant changes occurred over time for any of the other measured parameters for either sex. These data s uggest that skeletal muscle adaptations that may contribute to strengt h gains of the lower extremity are similar for men and women during th e early phase of resistance training and, with the exception of change s in the fast fiber type composition, that they occur gradually.