Grant: Travel Awards - Institute Community Support

Aging is accompanied by a progressive loss of skeletal muscle mass and strength known as sarcopenia. Although the causes are not yet determined, declining muscle mass is unavoidable and associated with immobility, increased fall risk and diseases such as type II diabetes. Furthermore, losses of physical function and muscle are accelerated in older adults by periods of inactivity commonly experienced with, for example, illness and hospitalization. We have previously shown that just two weeks of moderately reduced physical activity cause muscle loss in older adults, suggesting that nutritional and lifestyle interventions which maintain muscle and functional independence of the elderly are important for quality of life. In order to answer questions regarding mechanisms and limiting the consequences of sarcopenia, low-intensity strength exercise was investigated as a countermeasure to two-weeks of physical inactivity. Citrulline, a nutritional supplement meant to increase blood flow, nutrient delivery and stimulate muscle growth, was also investigated as a means of reducing the negative effects of an 80% reduction in daily walking (less than 1500 steps/day). Thirty healthy, older men were measured for changes in body composition, leg strength and molecular muscle protein synthesis with and without resistance training (3x/wk) and citrulline. The consequences of two-weeks of reduced daily walking included decreased muscle mass, leg strength and muscle protein synthesis in response to ingested protein. Strength exercises prevented losses in muscle, strength and the changes seen in protein synthesis, however citrulline was shown to be ineffective at limiting any of these consequences. Our research therefore highlights the effectiveness of even lightly loading the leg muscles over nutritional supplementation to rescue important properties of human muscle like strength, mass and sensitivity to nutritional protein in the face of reduced physical activity.