Exercise, psychological stress, physiologic stress, and immune function are interconnected. The immune system is closely related to the body's adaptive response to exercise.During the experience of stress, the hypothalamus activates the adrenal glands and thyroid gland (via the pituitary gland or via direct nerve pathways), which begin to produce cortisol, aldosterone, adrenaline, noradrenaline, and thyroxine. These hormones, in turn, induce a state of readiness for an active physical response by means of bodily processes.Conversely, in response to exercise and stress, cortisol and other hormones can suppress immune function. Conversely, in the presence of illness, the body's reaction to exercise is deleterious. The effect can be exacerbated by other stressors, including inadequate sleep, poor nutrition, alcohol consumption, and mental stress. The nature of the exercise modality also influences stress levels. Moderate exercise and slow-paced activities, such as yoga, have been shown to reduce cortisol levels and enhance emotional well-being. However, in the presence of underlying medical conditions and the engagement in exercises that stimulate the sympathetic nervous system, cortisol levels can exhibit both decreases and increases.
