Protecting muscle mass and function in older adults during bed rest.

To highlight the losses in muscle mass, strength, power, and functional capacity incurred in older adults during bed rest-mediated inactivity and to provide practical recommendations for both the prevention and rehabilitation of these losses. In addition to sarcopenic muscle loss, older adults lose lean tissue more rapidly than the young during prolonged periods of physical inactivity. Amino acid or protein supplementation has the potential to maintain muscle protein synthesis and may reduce inactivity-induced muscle loss, but should ideally be part of an integrated countermeasure regimen consisting of nutrition, exercise, and, when appropriate, pharmacologic interventions. In accordance with recent mechanistic advances, we recommend an applied, broad-based two-phase approach to limit inactivity-mediated losses of muscle mass and function in older adults: (i) Lifestyle: consume a moderate amount (25-30 g) of high-quality protein with each meal and incorporate habitual exercise in close temporal proximity to protein-containing meals; (ii) Crises: react aggressively to combat the accelerated loss of muscle mass and function during acute catabolic crises and periods of reduced physical activity. As a base strategy, this should include nutritional support such as targeted protein or amino acid supplementation and integrated physical therapy.