Steroid and pituitary hormone responses to rowing: relative significance of exercise intensity and duration and performance level.

To analyse the relative significance of exercise intensity and duration as well as performance capacity, hormone changes were recorded in 16 male rowers in two experiments separated by a year. The test exercises consisted of 7-min (at the supramaximal intensity) and 40-min rowing (at the level of the anaerobic threshold) on a rowing apparatus. In addition, somatotropin and cortisol responses were estimated in rowing for 8 x 2000 m in 14 rowers of national class. All three tests caused significant increases in somatotropin and cortisol concentrations in the blood. Follitropin concentrations were elevated in the 7-min exercise test in the second experiment and in the 40-min exercise test in both experiments. Lutropin and progesterone concentrations increased during the more prolonged exercise in the first experiment. No common change was found in testosterone concentrations. Cortisol and somatotropin response to the 40-min rowing test at anaerobic threshold were more pronounced than to the 7-min exercise test at supramaximal intensity. When the rowers achieved a national class level of performance (the second experiment) the hormone responses to 7-min supramaximal exercise were increased. During the 8 x 2000-m rowing test cortisol but not somatotropin concentration increased to an extremely high level in the rowers of national class. It is concluded that in strenuous exercise cortisol and somatotropin responses were triggered by the exercise intensity threshold. The exact magnitude of the response would seem to have depended on additional stimuli caused by exercise duration and on possibility of mobilizing hormone reserves.