Med Sci Sports Exerc. 2010 Dec 1. [Epub ahead of print]
Exercise Dosing to Retain Resistance Training Adaptations in Young and Older Adults.
Bickel CS, Cross JM, Bamman MM.
Departments of 1Physiology and Biophysics, 2Physical Therapy, and 3Surgery, University of Alabama at Birmingham, Birmingham, Alabama 35294; 4Geriatric Research, Education, and Clinical Center, Birmingham Veterans Affairs Medical Center, Birmingham, Alabama 35233.
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 old (60-75 y) vs. young (20-35 y).
METHODS: Seventy adults participated in a two-phase exercise trial that consisted of RT 3 d/wk for 16 wk (Phase I) followed by a 32 wk period (Phase II) with random assignment to detraining or one of two maintenance prescriptions (reducing the dose to 1/3 or 1/9 of that during Phase I).
RESULTS: Phase I 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 I muscle hypertrophy in young but not old. In fact, the 1/3 maintenance dose led to additional myofiber hypertrophy in young. In both age groups, detraining reversed the Phase I IIx-to-IIa myofiber type shift, while a dose-response was evident during maintenance training with the 1/3 dose better maintaining the shift. Strength gained during Phase I 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 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 untrained young.
