Strength and aerobic training attenuate muscle wasting and improve resistance to the development of disability with aging

By the age of 50 yrs old, humans become aware that they are losing muscle strength (mass) and endurance (mitochondria). A frequent symptom of neuromuscular disorders is muscle weakness (Walton, 1988). We define the aging-associated muscle wasting as a progressive neuromuscular syndrome that will lower the quality of life in the elderly by (1) decreasing the ability to lift loads (progressing to difficulty arising from a chair), and (2) decreasing endurance (leading to an inability to perform the activities of daily living, which increases health care costs). Campion (1994) states that the most successful outcome would be for the very elderly to take control of the last stage of their life and make it worth living. To obtain this goal, prevention of muscle wasting is an absolute requirement. Muscle mass and motor unit number, activation, and synchronization are highly related to strength; both decrease with aging (Rodgers and Evans, 1993). Resistance-training is the best way to increase muscle mass, neural coordination, and strength. Mitochondrial concentration is highly related to endurance capacity in young and old (Holloszy and Coyle, 1984). Both muscle contractile and mitochondrial protein decrease with aging in sedentary humans (reviewed by Rodgers and Evans, 1993). Endurance training, which is the best exercise to increase/maintain mitochondrial concentration with aging, has generally resulted in relatively small functional benefits to nursing home patients (Fiatarone et al., 1994). We speculate that those events leading to frailty consist of a severe loss of muscle mass (Buchner and Wagner, 1992), which limits mobility, which in turn further decreases muscle mitochondria an