Muscle can undergo atrophy from denervation or disuse, leading to a decrease in fiber size and contractile proteins. Increased contractile activity through exercise can cause hypertrophy, increasing fiber size and capacity for ATP production. Aerobic training increases mitochondria and capillaries, enhancing endurance. Strength training increases fiber diameter and muscle strength but less endurance. Exercise changes enzyme synthesis rates and the proportion of fiber types within a muscle.

1. Muscle Adaptation to Exercise

2. Atrophy: Denervation atrophy If the neurons to a skeletal muscle are destroyed or the neuromuscular junctions become nonfunctional, the denervated muscle fibers will become progressively smaller in diameter, and the amount of contractile proteins they contain will decrease.

3. Atrophy: Disuse atrophy A muscle with its nerve supply intact if the muscle is not used for a long period of time, as when a broken arm or leg is immobilized in a cast.

4. Hypertrophy Increased amounts of contractile activity (exercise) can produce an increase in the size of muscle fibers as well as changes in their capacity for ATP production.

5. Aerobic training (Exercise) exercise that is of relatively low intensity but of long duration ∞ increases in the number ofmitochondria in the fibers ∞ increase in the number of capillaries around these fibers ∞ increase in the capacity for endurance activity with a minimum of fatigue

6. Strength training (Exercise) short duration, high-intensity exercise that affects primarily the fast-glycolytic fibers, which are recruited during strong contractions ∞ increase in fiber diameter ∞ increase in the strength of the muscle and the bulging muscles of a conditioned weight lifter ∞ little capacity for endurance

7. Exercise produces little change in the types of myosinenzymes formed by the fibers and thus little change in the proportions of fast and slow fibers in a muscle does change the rates at which metabolicenzymes are synthesized, leading to changes in the proportion of oxidative and glycolytic fibers within a muscle

8. Aerobic Training Strength Training Effect on the cardiovascular system Partially prevent the loss of muscle tissue that occurs with aging Helps maintain stronger bones

9. MuscleSoreness extensive exercise by an individual whose muscles have not been used in performing that particular type of exercise result of a mild inflammation in the muscle, which occurs whenever tissues are damaged

10. Lever Action of Muscles and Bones

11. Flexion and Extension Flexion - bending of a limb at a joint Extension - Straightening of a limb

12. Antagonists groups of muscles that produce oppositelydirected movements at a joint

13. Flexion and Extension

14. Skeletal-Muscle Disease

15. Muscle Cramps Produces by involuntary tetanic contraction of skeletal muscles Nerve action potentials fire at abnormally high rates

16. HypocalcemicTetany The involuntary tetanic contraction of skeletal muscles that occurs when the extracellular calcium concentration falls to about 40% of its normal value.

17. Muscular Dystrophy Frequently encountered genetic diseases, most commonly in boys. Associated with the progressive degeneration of skeletal- and cardiac-muscle fibers, weakening the muscles and leading ultimately to death from respiratory or cardiac failure.

18. Myasthenia Gravis Characterized by muscle fatigue and weakness that progressively worsens as the muscle is used. Symptoms result from a decrease in the number of ACh receptors on the motor end plate.

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