A Comprehensive Analysis of Overtraining Syndrome in Athletes and Recreational Exercisers.

Overtraining syndrome (OTS) is characterised by persistent fatigue and performance decline, but it currently lacks specific diagnostic criteria and medical coding. Diagnosis is primarily based on a decline in maximal performance and a subjective feeling of 'staleness', after ruling out other medical conditions. This study aimed to identify physiological and self-reported predictors of OTS by comparing individuals diagnosed with OTS (n=110; 2008-2022) with a healthy control group (n=447; 2005-2023). Both groups consisted of athletes and recreational exercisers assessed at the Helsinki Sports and Exercise Medicine Clinic (HULA). Data were collected through questionnaires and spiroergometric testing and subsequently analysed using logistic regression, adjusting for age and sex. The results of this study suggest that fatigue, dizziness and shortness of breath, along with decreased maximum oxygen uptake (V̇O2_max), peak blood lactate value (La_max) and oxygen uptake at both ventilatory thresholds (V̇O_2VT1 and V̇O_2VT2), are significant predictors of OTS (p<0.05/54). Among reported health conditions, asthma, allergy, anaemia and mental health issues were statistically significant predictors of OTS at the 0.05 level, but not after Bonferroni correction. In conclusion, regular spiroergometric testing and symptom monitoring may support earlier diagnosis and improved management of OTS in athletes and recreational exercisers.