Abstract des Autors

The aim of the paper is to discuss the results of studies on endocrine activities in muscular activity in order to evaluate the principal factors which determine hormonal responses during the exercise. Special attention has been paid to conditions which modulate the influence of principal determinants. A great part of exercise-induced hormonal responses are related to exercise intensity. It is possible to define the threshold intensity of exercise as the minimum intensity needed to evoke hormonal changes in blood. However, a considerable amount of results demonstrate the dependence of the magnitude of hormonal responses on exercise duration. In this connection, the threshold duration of exercise comes into focus. It follows the fact that exercise of underthreshold intensity may result in hormonal responses when a given amount of work has been done. At intensities above the threshold, the threshold duration is expressed by a further increase of the hormonal response or by a secondary activation of the endocrine system. Systematic adaptation to exercise (training) induces (1) an increase in threshold intensity in terms of power output, thus the training reduces, partially or totally, the previously observed hormonal responses, (2) an elevated functional capacity of endocrine systems thus making possible very pronounced hormonal responses to extreme exercises. The significance of exercise intensity and fitness appears first of all in activities of endocrine systems responsible for a rapid mobilisation of energy reserves and protein resources. The activities of hormones controlling the water-electrolyte balance depends, first of all, on shifts in this balance. Consequently, homeostatic needs constitute the fourth determinant of hormonal responses besides exercise intensity, duration and fitness. The actualisation of the effect of principal determinants is modulated by several conditions, among those most striking is the influence of emotional state, environmental conditions and diet (availability of carbohydrates). Verf.-Referat