It is well known that sarcopenia (loss of muscle mass, strength, and quality of life) continues to be a problem for aging adults and a huge concern for the healthcare industry. Practical therapeutic options to counteract sarcopenia remain among the most urgent challenges of biomedicine in our aging society. To determine the usefulness of a countermeasure in attenuating/preventing sarcopenia; we need to measure its potency and sustainability. [1]

Potency should be assessed by the therapy’s ability to induce muscle regrowth and restore or improve muscle function.[1] Of all the therapies used to counteract sarcopenia (including pharmacologic); intense resistance training (RT) has consistently demonstrated the highest degree of potency by inducing hypertrophy and enhancing strength, power, and mobility.[2-4] Although there are age differences in RT-mediated muscle hypertrophy that favor the young[5], myofibers in older adults can regrow in as few as 4 months to reach the size of myofibers in untrained adults 40 yrs and younger [6].

The second key ingredient that defines efficacy of a countermeasure is its sustainability. Sustainability is a major limiting factor of utilizing RT as a therapeutic approach to sarcopenia. Exercise prescription is considered a very effective form of medical treatment (i.e. American College of Sports Medicine’s Exercise is Medicine initiative), but sustainability remains a challenge [1].

A more significant question that hasn’t yet been addressed in research is the minimum maintenance exercise dose required for preventing reversibility of muscle hypertrophy and function in older adults after a prolonged, progressive RT program. It is known that a continuous, comprehensive RT exercise program is ideal for enhancing muscle sized and strength; however many individuals will not continue their intensive program consistently over a prolonged period. Therefore, it is crucial to identify the minimum dose needed to promote sustainability if RT is to be embraced as a viable and broadly applicable countermeasure of sarcopenia [1].

A research group from the University of Alabama at Birmingham 1 conducted a study to determine the age-specific efficacy of two different exercise doses on maintaining gains in muscle mass, myofiber size, and voluntary strength, as well as maintenance of the type IIx-to-IIa shift in myofiber phenotype induced by a 16-wk period of intense, progressive RT in young (20-35 yr) and old (60-75 yr) adults.

They hypothesized that the minimum dose of RT required to maintain adaptations would be greater in older adults versus that in young. In order to test this hypothesis, they randomly assigned individuals to one of three groups after completing a 16-wk training program. The detraining/maintenance phase included a detraining control that stopped training and two programs that were equal to one-third or one-ninth of the weekly dose used to produce hypertrophy 6 during the 16-wk progressive RT program.

The 16-wk period of progressive RT (3 d/wk, 75-80% 1RM, 3 sets/exercise, and 8-12 reps/set) resulted in expected gains in strength, myofiber size, and muscle along with the typical IIx-to IIa shift in myofiber-type distribution. Muscle hypertrophy was preserved in the young, but not old during both maintenance prescriptions. Interestingly, the one-third maintenance dose (1 day/week, same intensity as 16-wk training period) led to additional gains in myofiber hypertrophy in the young.

Detraining reversed the IIx-to-IIa myofiber-type shift in both age groups, whereas a dose response was apparent during maintenance training with the one-third dose better maintaining the shift. Strength gained during the 16-wk RT period was mostly retained throughout detraining.

The consequences of sarcopenia-a major cause of physical frailty-are enormous and increasing each year as the older population continues to grow. The findings from this study and other research [7,8] strongly support RT as a primary intervention strategy to reduce the deleterious effects of sarcopenia. This data is the first to suggest that older adults require mores sets per week than younger individuals to maintain hypertrophy after an extended, progressive RT program.

Gains in specific strength among older adults were well preserved and remained at or above levels of untrained young. A comprehensive exercise program that continues indefinitely is ideal, but for many reasons, individuals will not continue their intensive program consistently due to vacations, work, family illnesses, etc. The important finding of this study is that during these times of limited training, the older population needs a higher dose of RT than the younger population in order to maintain muscle mass.

Gains in specific strength among older adults were well preserved and remained at or above levels of untrained young.

The dose equivalent to one-third of the initial 16-wk program that was utilized during the maintenance phase in this study was only 1 d/wk. Perhaps, 2 d/wk of RT would preserve the hypertrophy gains attained by the older population, but more research will be needed to verify this. The positive health benefits of increased muscle mass in the aging population extend well beyond muscle performance (e.g. glucose and fatty acid metabolism, aerobic capacity, and bone and joint health).

The important finding.... during times of limited training, the older population needs a higher dose of RT than the younger population in order to maintain muscle mass.

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Dr. Paul Henning is leading scientist at the Military Performance Division, United States Army Research Institute of Environmental Medicine. Paul's an avid bodybuilder, lives the MP lifestyle and is a proud member of the MP Team.

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1. Bickel CS, Cross JM, Bamman MM. Exercise dosing to retain resistance training adaptations in young and older adults. Med Sci Sports Exerc 2011;43:1177-87.

2. Borst SE. Interventions for sarcopenia and muscle weakness in older people. Age Ageing 2004;33:548-55.

3. Harridge SD, Kryger A, Stensgaard A. Knee extensor strength, activation, and size in very elderly people following strength training. Muscle Nerve 1999;22:831-9.

4. Hunter GR, McCarthy JP, Bamman MM. Effects of resistance training on older adults. Sports Med 2004;34:329-48.

5. Kosek DJ, Bamman MM. Modulation of the dystrophin-associated protein complex in response to resistance training in young and older men. J Appl Physiol 2008;104:1476-84.

6. Kosek DJ, Kim JS, Petrella JK, Cross JM, Bamman MM. Efficacy of 3 days/wk resistance training on myofiber hypertrophy and myogenic mechanisms in young vs. older adults. J Appl Physiol 2006;101:531-44.

7. Fiatarone MA, Marks EC, Ryan ND, Meredith CN, Lipsitz LA, Evans WJ. High-intensity strength training in nonagenarians. Effects on skeletal muscle. JAMA 1990;263:3029-34.

8. Frontera WR, Meredith CN, O'Reilly KP, Knuttgen HG, Evans WJ. Strength conditioning in older men: skeletal muscle hypertrophy and improved function. J Appl Physiol 1988;64:1038-44.

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