Biomarkers, Physiological Parameters, & Prevention Strategies of Overtraining Syndrome in Male Aerobic Athletes

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Background. Overtraining syndrome (OTS) is defined as an imbalance of exercise and rest that results in maladaptive adaptations. Symptoms of OTS are multisystemic and variable among individual athletes. Biomarkers such as adrenocorticotrophic hormone (ATCH) and cortisol have been investigated as a reflection of the Hypothalamic-Pituitary-Adrenal (HPA) axis' integrity. OTS affects athletes' health and performance; therefore, it is important to develop monitoring and prevention strategies. Purpose. The purpose of this literature review is twofold, first, to summarize the responses of biomarkers (ACTH & cortisol) and physiological parameters in overtrained male aerobic athletes; second, to provide suggestions for monitoring and preventing OTS. 29 Results. Hormonal response to exercise is an indicator of the HPA-axis' integrity and the body's ability to respond to stress. The HPA-axis' integrity is altered in athletes with OTS. ACTH and cortisol levels are blunted during exercise in athletes with OTS when compared to healthy athletes. Biomarker cut-points are not standardized, therefore physiological parameters like heart rate (HR) are used when monitoring OTS. Specifically, HR is significantly increased in athletes with OTS at rest and significantly decreased during submaximal and maximal exercise compared to healthy athletes. Evidence-based prevention strategies for OTS are lacking; however, monitoring training duration and ratings of perceived exertion (RPE), athletic performance, and mood disturbances are promising strategies that could be used for preventing the development of OTS. To prevent excess duration and exertion on athletes, periodized training is suggested. Unexplained decrease in sport performance is another sign of OTS. To measure decrements in performance, it is recommended to use time-to-fatigue sport-specific testing because it will show the greatest changes in exercise capacity. Lastly, mood questionnaires, such as the Profile of Mood State (POMS), can be used to measure changes in mood disturbances. The POMS questionnaire can be utilized to predict the impact of training intensity on an athlete's mood. As intensity increases without adequate rest, an athlete's mood will decrease significantly. Mood disturbance scores should influence programing with the goal of reducing the risk of developing OTS. Conclusion. In male aerobic athletes with OTS, the integrity of HPA-axis is altered leaving them unable to respond appropriately to exercise stress. Due to the blunted cortisol response and rapidly declining ACTH levels, they fatigue faster, recover slower, and have a decrease in performance. Monitoring training duration and RPE, athletic performance, and mood disturbances throughout training are possible strategies to prevent OTS.