Exercise, fitness, and stress

This paper addresses whether cardiorespiratory fitness or regular exercise result in cross-stressor adaptations, such that responses by the cardiac sy mpatho-vagal, sympatho-adrenal medullary, brain noradrenergic, and hypothal amic-pituitary-adrenal cortical systems are blunted or otherwise altered du ring stress other than exercise. An early meta-analysis of 25 studies of hu mans concluded that the aggregated effect of chronic exercise on physiologi cal reactivity to psychosocial stressors was about a half standard deviatio n reduction that did nor differ according to types of stressors or stress r esponses (Crews & Landers, 1987). That conclusion notwithstanding, there is no current consensus that cardiorespiratory fitness or regular exercise ar e accompanied by decreased physiological responsiveness to non-exercise str essors. Much of the available evidence on the topic evolved from a vague un derstanding of stress physiology and is scientifically weak. Our goals in t his paper are to describe that evidence and offer suggestions for reframing the question and improving the methods used to ask it.