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Aging is accompanied by a progressive loss of skeletal muscle mass and strength, leading to the loss of functional capacity and an increased risk of developing chronic metabolic diseases such as diabetes. The age-related loss of skeletal muscle mass must be due to a chronic disruption in the balance between muscle protein synthesis and degradation. In addition, it has been suggested that a decline in the number of satellite cells (SC) and/or their ability to become activated can contribute to the development of sarcopenia.

In healthy active older individuals, there does not seem to be a disturbance in muscle protein metabolism in the fasted (basal) state. Consequently, it has been proposed that older muscle has a deficit in the ability to regulate the protein synthetic response to anabolic stimuli, such as food intake and physical activity. Indeed, recent data suggest that the dose-response relationship between myofibrillar protein synthesis and the availability of essential amino acids and/or resistance exercise intensity is shifted down and to the right in elderly humans. This so-called anabolic resistance is now believed to represent a key factor responsible for the age-related decline in skeletal muscle mass. Although physical activity and/or exercise stimulate muscle protein synthesis in both the young and elderly, the hypertrophic response largely depends on the timed administration of amino acids and/or protein prior to, during, and/or after exercise. However, prolonged resistance type exercise training has been shown to be effective as a therapeutic strategy to augment skeletal muscle mass, increase muscle SC content, and improve functional performance in the elderly. The latter shows that the ability to increase muscle mass is preserved up to very old age. More research is warranted to elucidate the interaction between nutrition, exercise and the skeletal muscle adaptive response. The latter is needed to define more effective strategies that will maximize the therapeutic benefits of lifestyle intervention in the elderly.


Mary MacKillop Institute for Health Research

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Book Chapter

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