Plasma hormones and physical exercise.

The analysis of published data allowed us to establish main traits of blood hormone responses to exercises: There are stable changes in hormone levels that are common to all persons, as well as changes which are characterized by a polyphasic pattern and exhibiting inter-individual variability. By the response rate it is possible to discriminate fast responses, responses of a modest rate and delayed responses. Accordingly, mechanisms for a rapid and for a delayed activation exist. The changes mediated through the mechanism for a rapid activation depend on the intensity of exercise, revealing the threshold intensity for endocrine response. When a certain amount of exercise is done, the hormonal responses are triggered despite the under-threshold intensity of exercise. Consequently, a threshold duration of exercise also exists. Through training the threshold intensity of exercise increases and the functional capacities of the endocrine systems augment. The former results in the disappearance of hormonal responses during exercise intensity which was previously above the threshold. The latter makes it possible to achieve especially pronounced and long-lasting hormonal changes during extreme exercises. Emotional states as well as environmental conditions, and carbohydrate supply modulate the hormonal changes in exercise.