Skeletal Muscle Adaptations Following 80 Weeks of Resistance Exercise in Older Adults.

Background and purpose: We followed and documented skeletal muscle adaptations from 4 resistance exercise (RE) prescriptions in older adults over the course of a 2-year, 80-week training study.

Methods: Forty-three older men and women-65.2 (3.5) years, 167.2 (7.5) cm, and 72.5 (14.7) kg-completed one of the following RE prescriptions: high-load 2 days per week (HL2D; n = 12), low-load 2 days per week (LL2D; n = 9), high-load 3 days per week (HL3D, n = 12), or low-load 3 days per week (LL3D, n = 10). High-load prescriptions consisted of 3 sets of 8 repetitions with 80% 1-repetition maximum (1-RM) and low-load prescriptions completed 3 sets of 16 repetitions with 40% 1-RM. Each session consisted of 12 exercises targeting major muscle groups and training loads were adjusted every fifth week to maintain progressive overload. Participants completed 40 weeks of supervised training, had a 2-month break, and then resumed another 40 weeks of supervised training. Bone-free lean body mass (BFLBM) and appendicular lean mass (ALM) were assessed via dual-energy x-ray absorptiometry and muscle cross-sectional area (mCSA) of the rectus femoris with diagnostic ultrasound across the intervention.

Results and discussion: Groups responded similarly with significant increases in total strength (54.9%), upper body strength (42.7%), lower body strength (61.5%), and specific strength (50.3%, strength/BFLBM) over 80 weeks (all P < .001). Significant increases for BFLBM (3.0%), ALM (3.5%), and mCSA (48.7%) were also observed (all P ≤ .019). The only difference among groups indicated HL3D displaying significantly greater percent increase than LL2D for ALM (P = .043).

Conclusions: Resistance exercise performed 2 or 3 days per week with moderate to heavy loads can improve muscle strength and induce small but perhaps clinically significant increases in BFLBM and mCSA in older adults over a 2-year period of supervised training.