EFFICACY OF HEAVY-RESISTANCE TRAINING FOR ACTIVE WOMEN OVER 60 - MUSCULAR STRENGTH, BODY-COMPOSITION, AND PROGRAM ADHERENCE

Objective: To determine the effects of resistance training on muscular strength, body composition (percent fat and lean tissue mass), and program adherence in active women over 60 years of age. Design: This study was designed as a stratified, randomized, non-blinded trial. Subjects were stratified into rank-ordered pairs by level of physical activity according to the Blair Seven-Day Recall, then randomly assigned into either a weight-training (WT, n = 18) or control (CON, n = 18) group. Participants and Setting: Thirty-six women over the age of 60 (67.1 +/- 1.5, chi +/- SE) were recruited from the San Diego community. All subjects had to be engaging in some form of aerobic exercise at least 3 days each week for a minimum of 6 months. Measurements and Intervention: Subjects engaged in isotonic training 3 days/week on Polaris machines at a target intensity of 80% of the 1 repetition maximum (1 RM) for three sets of seven exercises selected to train major muscle groups of the trunk and upper and lower body. The 1 RM was re-tested every 6 weeks in WT and the workload adjusted to maintain target intensity. The 1 RM was tested at 0, 12, and 24 weeks in CON. Body fatness and lean tissue mass, excluding skeletal mass, were assessed at 0 and 24 weeks by dual energy radiography using a total body scan. Results: Increases in muscle strength of the weight trainers were significant for all seven exercises (5%-65%), with the greatest gains in the shoulder and trunk muscles. Percent body fat of weight trainers decreased significantly (from 38.8% to 37.9%, P < 0.05), while lean tissue mass increased by 1.5 kg (P < 0.01). No changes in body composition were observed in control subjects. Overall program adherence was 83% (15 weight trainers and 15 control women completed the study). Monthly attendance averaged 86.8 +/- 3.3%, with no incidence of injury during the training sessions. Conclusions: These data indicate that heavy-resistance weight training is safe and enjoyable for older women and that meaningful gains in muscular strength and body composition can be made even in women who are already highly active.