Hormonal responses to endurance training and overtraining in female athletes.

OBJECTIVE To examine different hormonal responses to heavy endurance training and overtraining in female athletes. DESIGN Submaximal and maximal treadmill tests, self-report mood measures, and stress hormone analyses were repeated at baseline, after 4 weeks and at the end of 6 to 9 weeks of experimental intensive training and after 4 to 6 weeks of recovery. SUBJECTS Fifteen healthy female endurance athletes increased their intensive training volume by 130% and base training volume by 100% (ETG, n = 9) or served as controls (CG, n = 6). MAIN OUTCOME MEASURES Maximal oxygen uptake (VO2max), mood dynamics, blood catecholamines, cortisol and testosterone at rest and after submaximal and maximal exercise, and nocturnal urine catecholamines. RESULTS Five females from the ETG demonstrated an over-training state (OA subgroup) at the end of the training period. Their VO2max decreased (mean +/- SEM) from 53.0 +/- 2.2 ml.kg-1.min-1 (range, 46.8-59.2) to 50.2 +/- 2.3 ml.kg-1.min-1 (range, 43.8-56.6) (p < 0.01). Maximal treadmill performance expressed as oxygen demand decreased (mean +/- SEM) from 56.0 +/- 1.6 ml.kg-1.min-1 (range, 51.5-60.5) to 52.2 +/- 1.1 ml kg-1.min-1 (range, 49.1-55.3) (p < 0.01). Maximal heart rate also decreased (mean +/- SEM) from 190 +/- 1 bpm (range, 185-197) to 186 +/- 2 bpm (range, 184-193) (p < 0.05), and the athletes experienced mood disturbances. Plasma adrenaline levels at maximal and noradrenaline at submaximal work rate decreased during the last 2 to 5 training weeks (p < 0.05), and serum cortisol levels at maximal work rate decreased during the first 4 training weeks (p < 0.05) in the ETG. Plasma adrenaline at maximal work rate decreased during the first 4 training weeks (p < 0.05) in the OA subgroup. There were no changes in the CG. Individual hormonal response types to heavy training and overtraining were found. CONCLUSIONS Hormone responses to exercise load are superior in indicating heavy training-induced stress when compared with resting hormone levels. These responses indicated decreased sympathoadrenal and/or adrenocortical activity (or exhaustion of the adrenal gland or the central nervous system). Individual hormonal profiles are needed to follow up training effects. Marked individual differences were found in training- and overtraining-induced hormonal changes.