The Effect of Exercise on Homeostasis
For your cells to function and thrive, they need a consistent internal environment. To maintain that environment, your body regulates your blood sugar, temperature, blood pressure, fluid and electrolyte levels and many other aspects of your physiology within narrow limits. This dynamic process is called homeostasis. By challenging your body's ability to maintain homeostasis, exercise stimulates the body to grow stronger and healthier.
Stress and Homeostasis
Anything that disrupts homeostasis is considered a stressor; exercise can be a healthy form of stress. Exercise disrupts homeostasis in many systems of the body, including the respiratory, circulatory, muscular and energy systems. Your body's response to stress is coordinated by a part of your brain called the hypothalamus, which stimulates endocrine organs as well as a part of your nervous system called the sympathetic nervous system.
Metabolic and Cardiovascular Homeostasis
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When you exercise, your muscles use energy. To provide fuel, the sympathetic nervous system stimulates the breakdown of fat from fat cells and the production of glucose, or blood sugar, by your liver. The stress hormone cortisol, produced by your adrenal glands, further stimulates the release of glucose from the liver. To get fuel and oxygen to your muscles, the sympathetic nervous system prompts your breathing rate to speed up and your heart to contract rapidly and forcefully. To shunt more blood to working muscles, blood supply to your digestive tract is reduced, slowing down digestion.
Heat and Fluid Regulation
The harder your muscles work, the more heat they produce. To keep your body temperature within safe limits, the sympathetic nervous system stimulates sweating, causing water loss. Rising blood pressure also forces fluid out of the bloodstream into the spaces between your cells. To maintain plasma volume, your pituitary gland releases anti-diuretic hormone and your adrenal glands secrete aldosterone. Both hormones cause water retention. Another hormone, called angiotensin II, works with aldosterone to maintain blood pressure.
Overtraining
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The goal of exercise is to overload your body just enough to disrupt homeostasis, but not so much that you can't bounce back. As long as your body gets sufficient nourishment and time for recovery, it will adapt and grow stronger. However, if the exercise is too extreme or if you don't allow for adequate recovery, exercise can become a negative stressor, leading to overtraining syndrome. Symptoms of overtraining syndrome include declining athletic performance and chronic exhaustion.
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References
- Exercise Physiology for Health, Fitness and Performance; Sharon A. Plowman and Denise L. Smith
- Exercise Physiology: Energy, Nutrition and Human Performance; William D. McArdle et al.
Writer Bio
Joe Miller started writing professionally in 1991. He specializes in writing about health and fitness and has written for "Fit Yoga" magazine and the New York Times City Room blog. He holds a master's degree in applied physiology from Columbia University, Teacher's College.