Muscular
System
The
major functions of this system are locomotion, support, and heat
production. When you hear the words “muscular
system” we are referring to skeletal muscle only (not cardiac
or smooth muscle).
As the
body ages, there is generally a reduction in the size and power of all
muscle tissues. In particular, skeletal muscle fibers become smaller in
diameter. The overall effect of this is reduced muscular strength and
endurance and a tendency to tire rapidly. Because the performance of
the heart also decreases, blood flow to active muscles does not
increase during exercise as rapidly as it does in younger people. |
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Not
so fun fact:
In
healthy young persons, 30% of body weight is muscle, 20% is adipose
tissue, and 10% is bone. Muscle accounts for 50% of lean body mass and
about 50% of the total amount of body nitrogen. By age 75, about 15% of
body weight is muscle, 40% is adipose tissue, and 8% is bone. Thus,
half the muscle mass has disappeared because of sarcopenia. |
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Skeletal
muscles also become less elastic. Aging skeletal muscles develop
increasing amounts of fibrous connective tissue, a process called
fibrosis. Fibrosis makes muscle less flexible so that movement and
circulation are restricted.
Tolerance for
exertion decreases. A lower tolerance for exercise results partly from
the tendency to fatigue rapidly and partly from the reduced ability to
eliminate heat generated during muscular contraction. Plus, the ability
to recover from muscular injury decreases.
Between the
ages of 30 and 75, overall lean body mass decreases primarily due to
reduced skeletal muscle mass. This loss is called sarcopenia and occurs
as the number and size of muscle fibers progressively decrease.
Despite
age-related reductions in muscle strength, muscle functional ability is
similar in older and younger adults. Usually, healthy elderly persons
can easily climb stairs, rise from a squatting position, walk along a
straight line, hop on either foot, and perform typical activities of
daily living. |
