Biologically, exercise conditions the body to deal with stress more effectively. It forces the body’s physiological systems to communicate more closely than usual. The cardio-vascular system communicates with renal system which communicates with the muscular system etc. All this is controlled by the central and sympathetic nervous system which serves as the command center for the bodies functions. As the body functions more efficiently, in all it’s individual capacities, it is better able to combat the destructive forces that attack our overall health and wellbeing.