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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