This study aimed to simplify and optimize the distinction between nonfunctional overreaching (NFO) and overtraining syndrome (OTS) by developing a multivariate approach (discriminant analysis [DA]) including hormonal and psychological changes measured during the Training Optimization (TOP) test. Methods Sensitivity of previously defined cutoff values for hypothalamic-pituitary-adrenal axis hormonal changes were recalculated on a larger database (n = 100). Discriminant analysis including hormonal and psychological variables measured during the TOP test was used to discriminate between NFO and OTS and predict the diagnosis of new cases. Results Adrenocorticotrophic hormone (ACTH) and prolactin (PRL) responses to the second exercise test were most sensitive to NFO and OTS. Cutoff values for ACTH and PRL response to the second test (NFO > cutoff value (200%) > OTS), showed a sensitivity of 67% for ACTH and 93% for PRL in case of OTS and 74% for both ACTH and PRL in case of NFO. A DA including hormonal and psychological changes measured during the TOP test, resulted in the accurate diagnosis of NFO and OTS with 98% sensitivity. The ACTH and PRL responses to the first and second exercise tests and feeling of fatigue were the most discriminating variables. Conclusions The ACTH and PRL responses during the TOP test are the most sensitive markers to discriminate between NFO and OTS. Discriminant analysis including hormonal and psychological responses during the TOP test, can be used to optimize the diagnosis of NFO and OTS.
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