Age-related changes in skeletal muscle function.

This review examines current evidence for the existence of aging processes in skeletal muscle fibers. Experimental data demonstrating changes with age in nerve-muscle interaction, excitation-contraction coupling, mechanical properties and muscle energetics are discussed, with emphasis on factors in addition to aging which might account for the observed results. The effects of dietary restriction, exercise and disease on age-related changes in muscle function are also discussed. Results of recent studies highlight the need to establish the health status of subjects and animals used for aging research as well as the need to obtain data from a wide variety of muscles. Although marked decline of muscle performance with age is documented by early studies, recent work indicates that at least some muscles of healthy individuals and animals do not show an age-related decline in function or an impaired ability to respond to exercise. Decreased physical performance in the elderly may be due to factors extrinsic to aged skeletal muscle fibers.