According to the Oxford Journals, exercise causes the body's homeostasis balance to increase the body's oxygen consumption, temperature, release of carbon dioxide and oxygen delivery. The body expends more energy during increased physical exertion, which results in increased breathing, sweating and heart rate.
Britannica defines homeostasis as the balance that the body maintains between several regulatory systems as a means of survival. This internal regulatory system kicks in as a response to outside stimuli. Homeostasis is a vital component of the body's in-house mechanistic nature and is literally a matter of life and death. If the body's homeostatic responses were to ever falter, it could potentially suffer a great deal of damage or even reach death.
According to the Oxford Journals, exercise is one example of an external stimulus which requires the body to increase its systematic response of several of its internal operations. For example, the energy created by exercise requires a drastic increase in the amount of oxygen which the body depends upon. As a homeostatic response to this increased oxygen demand, the body must also increase the rate at which oxygen is introduced into the bloodstream. The human body seeks to maintain this homeostatic balance at all times throughout the day, including when the body is asleep.