Alterations in body composition, physical function, and substrate metabolism occur with advancing age. Loss of skeletal muscle mass (sarcopenia) (1, 2) contributes to declines in muscle strength and function along with diminished quality of life (3). In the Baltimore Longitudinal Aging Study, quadriceps strength decreased about 30% between 50 –70 yr of age (4). In the Copenhagen Heart Study, leg strength in 80-yr-olds was 20 – 30% lower than in 70-yr-olds (5, 6). Substantial losses in strength may result in difficulty rising from a chair, climbing stairs, generating gait speed, and maintaining balance (7), eventually resulting in frailty. These changes contribute to loss of independence, social isolation, depression, and inactivity, thereby increasing the risk for disability, osteoporosis, and bone fractures. Advancing age is also associated with upper body obesity and insulin resistance, both risk factors for accelerated atherogenesis
