Exercise dosing to retain resistance training adaptations in young and older adults

Abstract

Resistance training (RT) is a proven sarcopenia countermeasure with a high degree of potency. However, sustainability remains a major issue that could limit the appeal of RT as a therapeutic approach without well-defined dosing requirements to maintain gains.

Purpose: To test the efficacy of two maintenance prescriptions on muscle mass, myofiber size and type distribution, and strength. We hypothesized the minimum dose required to maintain RT-induced adaptations would be greater in the old (60-75 yr) versus young (20-35 yr).

Methods: Seventy adults participated in a two-phase exercise trial that consisted of RT 3 d·wk for 16 wk (phase 1) followed by a 32-wk period (phase 2) with random assignment to detraining or one of two maintenance prescriptions (reducing the dose to one-third or one-ninth of that during phase 1).

Results: Phase 1 resulted in expected gains in strength, myofiber size, and muscle mass along with the typical IIx-to-IIa shift in myofiber-type distribution. Both maintenance prescriptions preserved phase 1 muscle hypertrophy in the young but not the old. In fact, the one-third maintenance dose led to additional myofiber hypertrophy in the young. In both age groups, detraining reversed the phase 1 IIx-to-IIa myofiber-type shift, whereas a dose response was evident during maintenance training with the one-third dose better maintaining the shift. Strength gained during phase 1 was largely retained throughout detraining with only a slight reduction at the final time point.

Conclusions: We conclude that older adults require a higher dose of weekly loading than the young to maintain myofiber hypertrophy attained during a progressive RT program, yet gains in specific strength among older adults were well preserved and remained at or above levels of the untrained young.