GLOSSARY

Homeostasis is the body’s ability to maintain a stable internal environment despite changes in the external environment or those caused by physical activity.
The word comes from the Greek homoios, meaning “similar,” and stasis, meaning “standing still.” Variables such as body temperature, blood glucose, blood pH, blood pressure, and water and electrolyte balance are kept within a narrow range.

Mechanism

Every regulatory system has three components: a receptor that senses the change, a control center, usually the brain or a gland, and an effector that produces the response.
Most of this regulation works through negative feedback, meaning the body’s response acts in the opposite direction to the change.

Relevance to Sport

Exercise is one of the greatest challenges to homeostasis; when running in hot weather, for example, the rise in body temperature is sensed by the hypothalamus, and the body dissipates heat through sweating and widening the skin’s blood vessels.
In intense activity, the accumulation of hydrogen ions lowers muscle pH, and the respiratory system removes carbon dioxide through faster breathing to maintain acid-base balance.

Key Teaching Point

Regular training increases the body’s ability to maintain homeostasis; a trained athlete sweats earlier, has a larger plasma volume, and is more resistant to heat and fatigue. A severe disruption of homeostasis, such as heat stroke, is a medical emergency.