Effects of age and resistance training on skeletal muscle: a review.

As humans age, there is a decrease in the ability of skeletal muscle to generate force. This review describes alterations in the neuromuscular systems of humans and animals that may be responsible for the diminished force-generating capacity of older muscles. The effects of resistance training on the force-generating capacity of older muscles in humans and on the neuromuscular systems of humans and animals are then examined. The age-related decline in force-generating capacity may be due, in part, to a loss of motor units and to a decline in muscle mass. Fiber atrophy and, possibly, loss of muscle fibers contribute to the decline in muscle mass in older persons. High-intensity resistance training appears to attenuate the age-related decline in force-generating capacity in humans and cause fiber hypertrophy of old muscle fibers. Investigations of the effects of age on the neuromuscular system and of the effects of resistance training on the neuromuscular system and the functional capacity of older persons are essential for the development of cost-effective interventions that will increase the physical capacity of older persons.