The Effect of Exercise on the Hypothalamic–Pituitary–Adrenal Axis

Current knowledge of the relationship between the HPA axis and physical exercise in normal and highly trained individuals highlights the importance of adequate preparation for exercise. The activation of the HPA (hypothalamic–pituitary–adrenal) axis in response to physical activity in humans has been abundantly reported. The HPA axis consists of three structurally independent components including the hypothalamus, the anterior pituitary, and the adrenal cortex. These structures are intimately interacting through the release of neuroendocrine messengers and the activation or the inhibition of the nervous system influencing the functions of most organs and tissues in the body. Such interactions imply among others peptide hormones CRF (corticotrophin-releasing factor), ACTH (adrenocorticotropic hormone), and arginine vasopressin (AVP) and their specific receptors, as well as smaller molecular species such as corticosteroids. The information summarized in this chapter points out that the HPA axis importantly influences stress-induced functions and that the intensity of HPA axis activation is intimately related to the type of training and the intensity at which it is performed. Altogether, these effects indicate the influences of the activation of the HPA axis in physical activity.