Objective: To study if a two bout exercise protocol can be used to make an objective, immediately available distinction between non-functional overreaching (NFO) and overtraining syndrome (OTS).
Design: Underperforming athletes who were diagnosed with the suspicion of NFO or OTS were included in the study. Recovery of the athletes was monitored by a sports physician to retrospectively distinguish NFO from OTS.
Setting: Sports medicine laboratory.
Participants: Ten underperforming athletes started and completed the protocol. Five athletes were retrospectively diagnosed with NFO and five were diagnosed with OTS.
Interventions: A two bout maximal exercise protocol was used to measure physical performance and stress induced hormonal reactions.
Main outcome measurements: Exercise duration, heart rate and blood lactate concentration were measured at the end of both exercise tests. Venous concentrations cortisol, adrenocorticotrophic hormone (ACTH), prolactin and growth hormone were measured both before and after both exercise tests.
Results: Maximal blood lactate concentration was lower in OTS compared to NFO, while resting concentrations of cortisol, ACTH and prolactin concentrations were higher. However, sensitivity of these measures was low. The ACTH and prolactin reactions to the second exercise bout were much higher in NFO athletes compared to OTS and showed the highest sensitivity for making the distinction.