Muscular System and Aging
The slower movement, weakness, and altered physical appearance are largely a result of changes in the muscular and skeletal system.
With age, the muscles decrease in size as a result of loss of muscle fibers and atrophy of individual muscle fibers. There is also a loss of motor units. There is greater loss of fast twitch fibers, partly a re-sult of aging and partly a result of disuse. The vascu-larity decreases and more fat is deposited in the mus-cle. The atrophied muscles are replaced with fibrous tissue, reducing elasticity. Changes in muscle, as well as the nervous system, slow movement and decrease strength and endurance. The rate of loss of strength and endurance can be significantly reduced by resis-tance exercise. Changes in the vertebral column, stiff-ening of ligaments and joints, and hardening of ten-dons result in mild flexion of the vertebrae, hips, knees, elbows, wrists, and neck.
The changes in muscle function may be partly at-tributed to effects of age on the nervous system. The extrapyramidal system is impaired and this results in mild tremors at rest. There is a decline in the number of spinal cord axons and in nerve con-duction velocity. Voluntary responses that involve re-action and/or movement are slower; however, the de-cline is less in those who maintain an active lifestyle.
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