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

Abstract

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. 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 × 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 × 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). 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 LI-3D. The variety of effective RE approaches provides flexibility among older adults for selecting a lifestyle intervention that would be most sustainable.