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- Physiologic Responses and
Long-Term Adaptations to Exercise
- Physical Activity and
Health: A Report of the Surgeon General
When challenged with any physical
task, the human body responds through a series of integrated changes in function
that involve most, if not all, of its physiologic systems. Movement requires
activation and control of the musculoskeletal system; the cardiovascular and
respiratory systems provide the ability to sustain this movement over extended
periods. When the body engages in exercise training several times a week or more
frequently, each of these physiologic systems undergoes specific adaptations
that increase the body’s efficiency and capacity. The magnitude of these
changes depends largely on the intensity and duration of the training sessions,
the force or load used in training, and the body’s initial level of fitness.
Removal of the training stimulus, however, will result in loss of the efficiency
and capacity that was gained through these training-induced adaptations; this
loss is a process called detraining.
This chapter provides an overview of how
the body responds to an episode of exercise and adapts to exercise training and
detraining. The discussion focuses on aerobic or cardiorespiratory endurance
exercise (e.g., walking, jogging, running, cycling, swimming, dancing, and
in-line skating) and resistance exercise (e.g., strength-developing exercises).
It does not address training for speed, agility, and flexibility. In discussing
the multiple effects of exercise, this overview will orient the reader to the
physiologic basis for the relationship of physical activity and health.
Physiologic information pertinent to specific diseases is presented in the next
chapter. For additional information, the reader is referred to the selected
textbooks shown in the sidebar.
Conclusions
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Physical activity has
numerous beneficial physiologic effects. Most widely appreciated are its
effects on the cardiovascular and musculoskeletal systems, but benefits on
the functioning of metabolic, endocrine, and immune systems are also
considerable.
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Many of the beneficial
effects of exercise training - from both endurance and resistance
activities - diminish within 2 weeks if physical activity is substantially
reduced, and effects disappear within 2 to 8 months if physical activity
is not resumed.
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People of all ages,
both male and female, undergo beneficial physiologic adaptations to
physical activity.
Selected Textbooks
on Exercise Physiology
Astrand PO, Rodahl K. Textbook
of work physiology. 3rd edition. New York: McGraw-Hill Book Company, 1986.
Brooks GA, Fahey TD, White TP.
Exercise physiology: human bioenergetics and its applications. 2nd
edition. Mountain View, CA: Mayfield Publishing Company, 1996.
Fox E, Bowers R, Foss M. The
physiological basis for exercise and sport. 5th edition. Madison, WI: Brown
and Benchmark, 1993.
McArdle WD, Katch FI, Katch
VL. Essentials of exercise physiology. Philadelphia, PA: Lea and Febiger,
1994.
Powers SK, Howley ET. Exercise
physiology: theory and application to fitness and performance. Dubuque, IA:
William C. Brown, 1990.
Wilmore JH, Costill DL. Physiology
of sport and exercise. Champaign, IL: Human Kinetics, 1994.
Centers for Disease Control and Prevention
National Center for Chronic Disease Prevention and Health Promotion
Division of Cancer Prevention and Control
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Activity and Your Health: Physiologic Responses and Long Term Adaptations to
Exercise
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