EFFECTS OF ENDURANCE TRAINING ON HORMONAL RESPONSES TO PROLONGED PHYSICAL EXERCISE IN MALES

The effect of several years' endurance training on hormonal changes during acute prolonged physical exercise was studied. In trial 1, 13 cross-country skiers were studied before and after a 75-km ski race and 3 weeks later on a control day. In trial II, 10 trained and 8 untrained subjects bicycled for 4 h on the road with as high a performance level as possible. Venous blood samples were taken in both trials before and after the exercise. In trial 1, serum concentrations of luteinizing hormone (p < 0.01) and follicle-stimulating hormone (FSH, p < 0.001) decreased more from morning to afternoon samples, and cortisol (p < 0. 001) and growth hormone (GH, p < 0.001) increased more during the ski race when compared to the control day. Serum testosterone decreased during the ski race (p < 0.01) but not on the control day. In trial II, a group difference was seen in serum FSH levels which was higher in the trained than untrained subjects at all three time points (F = 4.66, p = 0.046). A significant trial-group interaction (p = 0.020) was seen in GH, the GH being lower before exercise and higher 2 h after exercise in the untrained subjects. There was a significant group contrast between pre- and post-exercise samples in testosterone (p = 0.021) and cortisol (p = 0.022). In conclusion, the higher basal FSH concentration in the trained versus untrained subjects may be a sign of compensated hypogonadism due to intensive chronic training or it may be due to dysfunction of Sertoli cells. Signs of adaptation to resist the hormonal changes caused by acute physical exercise can be seen in the trained subjects when compared to the untrained subjects.