Melatonin levels and exercise in adolescent boys and girls

Saliva concentrations of the indolamine melatonin were measured in adolesce nts of both genders who were typed as sedentary (only performing school phy sical activities) and sport-loving (school physical activity and at least 3 hours/week extracurricular exercise) after they had carried out an uninter rupted physical trial at an intensity between moderate (pulse-rate 120 beat s/min) and submaximal (180 beats/min). Samples were collected before and af ter the physical trial and again at 23:00 h. The saliva melatonin levels we re determined by radioimmunoassay. The results indicated that the sports gi rls presented higher melatonin levels than the sedentary girls in basal con ditions, and that the physical trial raised these levels in both groups of girls. Extracurricular physical activity led to no differences in the basal melatonin levels between the two groups of boys, and there were no signifi cant changes observed after the exercise trial in either group. The nocturn al levels of melatonin were the highest in all four groups.