Hormonal responses in athletes: the use of a two bout exercise protocol to detect subtle differences in (over)training status

Eur J Appl Physiol. 2004 Mar;91(2-3):140-6. doi: 10.1007/s00421-003-0940-1. Epub 2003 Oct 2.


In overtrained athletes, several signs and symptoms have been associated with the imbalance between training and recovery. However, reliable diagnostic markers for distinguishing between well-trained, overreached (OR) and overtrained (OT) athletes are lacking. A hallmark feature of overtraining syndrome (OTS) is the inability to sustain intense exercise and recover for the next training or competition session. We therefore devised a test protocol utilizing two bouts of maximal work. With this test protocol we tried to establish a difference in hormonal responses between the training status of T and OR athletes. Seven well-trained cyclists participated in this study and were tested before and after a training camp. We also present the data of one OT motocross athlete who was clinically diagnosed as overtrained. All athletes performed two maximal exercise tests separated by 4 h. Blood was analyzed for cortisol, adrenocorticotrophic hormone (ACTH), growth hormone and prolactin (PRL). Performance decreased by 6% between the first and the second exercise test in the OR group and by 11% in the OT subject. Moreover, during the second exercise test there were more marked differences between the T and OR athletes; in particular, the OT subject did not show an increase in some of the hormonal responses. PRL increased only by 14% in the OT subject's second test and there was a 7% decrease in ACTH. The two exercise approach enables us to detect subtle performance decrements that will not be identified by one exercise trigger. The hormonal responses to the second exercise test were different between the T and OR athletes (the increase in the T group was higher than in the OR that was higher than in the OT). The results of the case presentation of an overtrained athlete provide evidence of an altered and dysfunctional hypothalamic-pituitary axis response to two bouts of maximal exercise. These findings can be used to develop markers for diagnosis of OTS and to begin to address the pathologic mechanism operative in the syndrome, as well as providing an outcome measure to evaluate possible therapeutic regimes.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Adaptation, Physiological / physiology
  • Adrenocorticotropic Hormone / blood
  • Adult
  • Bicycling / physiology*
  • Exercise / physiology*
  • Exercise Test / methods*
  • Exercise Tolerance / physiology*
  • Growth Hormone / blood
  • Hormones / blood*
  • Humans
  • Hydrocortisone / blood
  • Male
  • Muscle Fatigue / physiology*
  • Physical Education and Training / methods*
  • Prolactin / blood
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Sports / physiology


  • Hormones
  • Adrenocorticotropic Hormone
  • Prolactin
  • Growth Hormone
  • Hydrocortisone