A fundamental question in the theory of psychobiological adaptation and specifically of sports training is the problem of how adaptation to sports performance demands occurs as a consequence of systematic exercise. In this position paper, we review some results of our previous and current research conducted on several different levels of exercise-induced effects. Based on these results, we contend that the control of psychobiological systems during exercise is constraints based. Constraints direct the flow of behavioral changes on a rugged metastable landscape. Such adaptive behavior is soft-assembled, consisting of context-sensitive cooperative configurations of system components that dwell on different time scales.