The endocrine response to physical activity.

Physical activity is characterized metabolically by a relatively greater demand for combustion of carbohydrate and in addition by increased strain on several other physiological processes. Training tends to reduce the impact of physical activity on most organ systems. Physical activity, when it is not exhaustive, usually leads to elevated blood levels of "hormones of stress and activity" (catecholamines, cortisol, growth hormone), while thyroid and gonadal secretions are less involved. Following a period of training the endocrine response seems to abate, whether due to increased peripheral hormone sensitivity or to reduced need.