American Academy of Health and Fitness
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IN THIS SECTION
Integumentary (Skin) System
Skeletal System
Muscular System
Nervous System
Endocrine System
Cardiovascular System
Lymphatic (Immune) System
Respiratory System
Digestive System
Urinary System
Reproductive System


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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.

 

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.

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.

 
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