This essay reviews scientific literature regarding the possible effect of exercise on sleep physiology in non-clinical individuals. Exercise and sleep as research phenomena in the literature is examined, documented experimental evidence and theories on the possible mechanisms of a sleep-exercise relationship is reviewed, and suggestions for future research is made. Exercise and sleep are wide-ranging phenomena with a multitude of variables and aspects, making them difficult to research. Although exercise having historically and popularly being favorably associated with sleep, the objective scientific evidence for such a relationship is conflicting.This possibly due to studies using differing methods of various quality and focusing on different aspects of the object of research. There are several theories regarding how an exercise-sleep connection could function, none has yet to be substantiated by existing evidence.