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

The effect of several years' endurance training on hormonal changes du ring acute prolonged physical exercise was studied. In trial 1, 13 cro ss-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 leve l as possible. Venous blood samples were taken in both trials before a nd 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 d uring 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 t he trained than untrained subjects at all three time points (F = 4.66, p = 0.046). A significant trial-group interaction (p = 0.020) was see n in GH, the GH being lower before exercise and higher 2 h after exerc ise 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 concentrati on in the trained versus untrained subjects may be a sign of compensat ed hypogonadism due to intensive chronic training or it may be due to dysfunction of Sertoli cells. Signs of adaptation to resist the hormon al changes caused by acute physical exercise can be seen in the traine d subjects when compared to the untrained subjects.