The influence of sex, training intensity, and frequency on muscular adaptations to 40 weeks of resistance exercise in older adults

The purpose of this investigation was to identify the influence that sex, training intensity, and frequency have on long-term resistance exercise (RE) outcomes in older adults. Methods: One-hundred eleven older adults (men: 41, women: 70) completed either: high-intensity RE 2d/week (HI-2D; n = 29), low-intensity RE 2d/week (LI-2D; n = 32), high-intensity RE 3d/week (HI-3D, n = 20), or low intensity RE 3d/week (LI-3D, n = 30). HI protocols completed 3 sets of 8 repetitions with 80% one-repetition maximum (1-RM) while LI completed 3 sets of 16 repetitions with 40% 1-RM. Total and regional bone free lean body mass (BFLBM) were assessed via dual-energy x-ray absorptiometry and cross-sectional area (mCSA) of the rectus femoris. Results: mCSA was the only muscle quantity parameter to increase (p = 0.043). Significant trial effects for upper body, lower body, and specific strength were observed (all p < 0.001). Significant sex x time interactions (p < 0.001) were observed for upper and lower body strength, however, men and women displayed similar increases in lower body (45.7 +/- 29.6 vs 46.4 +/- 34.9%), upper body (33.1 +/- 21.0 vs 33.4 +/- 24.7%), and specific strength (36.5 +/- 28.5 vs 40.1 +/- 28.7%). A group x time interaction for lower body strength indicated that at 20-weeks HI 2D and LI-3D displayed greater lower body strength than LI-2D (both p < 0.009), and at 40-weeks HI-2D, HI-3D, and LI-3D displayed significantly greater lower body strength than LI-2D (all p 0.038). Conclusions: These observations indicate that older men and women display similar long-term RE outcomes. Additionally, regardless of frequency or intensity, the current prescriptions were effective for increasing strength, however these data suggest HI-2D LI-2D and LI-3D > LI-2D but similar outcomes among HI-2D, HI-3D, and LI3D. The variety of effective RE approaches provides flexibility among older adults for selecting a lifestyle intervention that would be most sustainable.