"On exercise and stress."

The stress-response is about preparing your body for an explosive burst of energy consumption right now; psychological stress is about doing all the same things to your body for no physical reason whatsoever. Exercise finally provides your body with the outlet that it was preparing for.

— Why Zebras Don't Get Ulcers, by Robert M. Sapolsky, p. 255.

quoted by Paul Ingraham on PainScience.com