I’m listening to the excellent “Born to Run” (Christopher Macdougal, if memory serves), about running, and in particular about the Tarahumara Indians in Mexico. A case is made there that there is an intrinsic connection between a cheerful, generous disposition and athletic excellence.
Logically, nervous system efficiency is tied to relaxation, which is tied to non-violence. You do not force yourself to do anything you don’t WANT to do. Elite athletes WANT to perform well, they enjoy the process, so they are efficient.
Logically, too, if we consider that the brain alone uses 20% of our daily calories, a relaxed, cheerful disposition ought to use less calories than a tense, constricted one. This is likely the secret of people like the marathon monks of Mount Hiei, who eat much less than one would think they would need.