Walter Cannon (1871–1945), the first professor of physiology at Harvard University, investigated the specific mechanisms whereby the human body responds to changes in the external environment while maintaining optimal function. He began with an idea of the French physiologist Claude Bernard (1813–1878): that people exist in an inter­nalized fluid environment and have evolved mech­anisms to ensure the optimal physiologic activity of cells and organs by keeping this environment constant.

Cannon used the term homeostasis for this process of maintaining internal stability in a changing external environment. The human body, as a biologic system, is organized to respond psy­chologically and physically to constantly changing external conditions. It can tolerate only a narrow range of environmental conditions.

Within the limits of its physiology, the body activates self-regulation mechanisms to maintain homeostasis, including self-repair mechanisms when damage occurs and compensatory mechanisms when self-repair cannot be achieved. Compensatory mech­anisms ensure the continuation of body function for survival at the expense of homeostasis. These mechanisms provide a biologic response to the changing environment for the survival of the sys­tem. Sufficiently severe environmental conditions result in partial destruction of the orderly working of the body or in death, the complete cessation of systems-level function.

Homeostasis is critical to athletic performance. Homeostasis in sport and exercise which is dif­ferent from homeostasis in daily life is called sport homeostasis. It implies the balanced mechanical function of the musculoskeletal system in addition to the traditional homeostatic condition of other physiologic systems, such as the cardiovascular or endocrine system.

Human beings can experience optimal movement only when the musculoskeletal system maintains balance in both its mechanical and physiologic aspects. With optimal biomechan­ical homeostasis, body movement is at its best because all the muscles and joints are in harmoni­ous coordination without the expense of compen­satory mechanisms.

For example, sports medicine research has demonstrated that lower back pain causes weakness of the core muscle, which results in slower movement of the hips and lower limbs. Athletes with lower back pain run more slowly and consume more energy with every motion.

When the musculoskeletal system is functioning with this kind of reduced efficiency, athletes have reduced reaction time; they fatigue easily and are more vulnerable to injury; psychological depression may be present and pre-competition anxiety may be worse; and post exercise recovery may be delayed.

Therefore it should be understood that homeo­stasis of musculoskeletal mechanics is a part of physiologic homeostasis, which includes cardiovas­cular, respiratory, and metabolic physiology, and all these aspects are regulated by the same part of the brain: the hypothalamus.