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Objectives—To evaluate the hormonal response to strenuous endurance exercise performed by elite athletes.
Methods—Nine professional cyclists (mean (SD) age 28 (1) years; mean (SD) VO2MAX 75.3 (2.3) ml/kg/min) who participated in a three week tour race (Vuelta a España 1999) were selected as subjects. Morning urinary levels of 6-sulphatoxymelatonin (aMT6s) and morning serum levels of testosterone, follicle stimulating (FSH), luteinising hormone (LH), and cortisol were measured in each subject at t0 (before the competition), t1 (end of first week), t2 (end of second week), and t3 (end of third week). Urine samples of aMT6s were also evaluated in the evening at t0, t1, t2, and t3.
Results—Mean urinary aMT6s levels had increased significantly (p<0.01) during the day after each stage (1091 (33) v 683 (68) ng/ml at t1; 955 (19) v 473 (53) ng/ml at t2; 647 (61) v 337 (47) ng/ml at t3). Both morning and evening aMT6s levels decreased significantly during the study. A similar pattern was observed for morning serum levels of cortisol and testosterone.
Conclusions—The results suggest that the basal activity of the pineal gland, adrenal glands, and testis may be decreased after consecutive days of intense, long term exercise.
Key Words: melatonin; gonadotrophins; testosterone; cortisol; endurance exercise