In a recent systematic review, researchers evaluate the roles of hormones in overtraining syndrome.
Trained athletes are aware that recovery periods away from training are just as significant as the time spent training. Inadequate rest and nutrition can lead to overtraining syndrome (OTS) among athletes, compounding problems concerning muscle fatigue, hormone, and metabolic function. An example of overtraining is functional overreaching [FOR], and non-functional overreaching [NFOR], characterized by decreased physical or mental performance within a set time frame. Current literature offers no distinct biomarkers to aid in diagnosing OTS and its related states.
To determine which biomarkers are conclusively linked to OTS, FOR, or NFOR, studies in PUBMED, MEDLINE, and Cochrane databases were gathered using keywords specific to OTS. Studies conducted up to June 15th, 2017 were vetted under the following search criteria:
1) The entirety of the article be in English
2) Hormone profile and correlation to OTS/NFOR/FOR states as an outcome, but not necessarily the primary outcome
3) No hormone-therapy-biased articles
4) Absence of diseases that could cause impaired hormonal status unrelated to OTS
5) A subject group properly diagnosed with OTS/NFOR/FOR
6) Human subjects for study
These criteria yielded 38 studies, narrowed down from 835 articles. A mix of sports was represented across these results such as cycling, triathlons, and weightlifting, among others. The most common test for analysis (performed in 24 out of 38 studies) was a resting hormone level evaluation after inducing an NFOR/FOR state in the subject. Of the studies evaluated, 16 demonstrated acute hormone responses to stimulation tests. Among these, nine measured baseline and stimulated hormonal effects, whereas seven tested hormone responses after functional testing and a physical stress test training program.
The review, published in BMC Sports Science, Medicine and Rehabilitation, observed inconclusive evidence to build a reliable framework for overtraining syndrome diagnosis. The studies utilized were limited by the wide variety of sports evaluated, small participant numbers, and lack of consistent OTS/NFOR/FOR benchmarks. The inconsistency in the data used did not provide the research team as comprehensive a review as they had hoped. However, the data proposed that baseline hormone levels are not indicative of reliable markers for OTS/NFOR/FOR, yet acute responses measured in association with stimulated hormones such as ACTH, GH, and prolactin may good predictors.
Overtraining syndrome is a complex disorder with much minutiae in the observed variables to consider. This review should provide a foundation for future studies to draw upon to make more sound conclusions regarding this and similar illnesses.
Written by Cooper Powers, BSc
Reference: Cadegiani, F., Kater, C. (2017). Hormonal aspects of overtraining syndrome: a systematic review. BMC Sports Science, Medicine and Rehabilitation, 9(14). Retrieved from https://bmcsportsscimedrehabil.biomedcentral.com/articles/10.1186/s13102-017-0079-8