Description: While exercise is pretty much universally recommended as a disease-preventer and important contributor to good health, there's a surprising dearth of studies supporting this premise. Most recommendations for exercise have come from epidemiological studies, which may find associations between, say, activity and better health, but do not prove that it's the activity itself that's is causing improvement. Active individuals may, after all, smoke less or eat more healthily than less active individuals, and it may be these factors that are responsible for the apparent relationship between activity and enhanced health.