Free weight resistance training alters body composition in middle-aged women depending on menopause - A 20-week control trial study

Abstract

Abstract Background: Resistance training (RT) is effective in counteracting the age- and menopause-related loss of muscle mass (MM) and strength in middle-aged women (40-60 years). Research on RT with free weights in this population is limited in pre- and postmenopausal women. Based on this, a 20-week training intervention was conducted with middle-aged women to investigate the effects of systematic strength training with free weights on strength capacity and body composition. Method: Forty-one healthy women (52.0±3.6 years) participated in this study. A 10-week control phase (no strength training, T0-T1) was followed by a 10-week intervention phase (T1-T2) with RT twice a week and 6-8 sets of each muscle per week. Subjects were randomly assigned to a low-intensity (50% 1-RM) or moderate-intensity (75% 1-RM) RT group and divided into pre-menopausal (PreMeno) and post-menopausal (PostMeno) according to their hormone profile. Fat-free mass (FFM), MM, fat mass (FM), muscle thickness (Vastus lateralis (VL), Rectus femoris (RF), Triceps brachii (TB), grip strength, 1-RM squat and bench press were assessed before and after each phase. Statistical analysis was used a linear mixed model to account for fixed (time and group) and random effects (individual). Results: A total of 31 women successfully completed the study. No injuries occurred during the intervention. Significant increases in 1-RM were observed in all groups. No interaction effect was observed for the strength parameters. In premenopausal women, FFM, MM and RF muscle thickness increased significantly, while VL showed a trend. These effects were not present in postmenopausal women regardless of RT intensity. Conclusion: RT with free weight is safe and effective for middle-aged women to increase 1-RM. Hypertrophy effects were found exclusively in premenopausal women. To achieve hypertrophy and/or body composition changes in postmenopausal women, larger training volumes (>6-8 sets/muscle per week) are likely required.