A Review of Overtraining Syndrome (OTS)
Table 1. ECSS terminology of overtraining syndrome (Meeusen et al)
The central fatigue hypothesis centers around the neurotransmitter serotonin. Serotonin competes with branched chain amino acids for entry into the brain and exercise has been shown in the past to create increased levels of unbound tryptophan (Budgett et al, Armstrong et al). Unfortunately, ew studies have evaluated the levels of serotonin in association with exercise. Of available literature, it has been noted that by giving serotonin reuptake inhibitors to athletes which artificially increase the levels of serotonin in the brain can have a negative impact on athletic performance (Budgett et al).
Figure 1. Symptoms of overtraining syndrome (courtesy of metrifit.com)
Overtraining syndrome is a clinical diagnosis mostly through historical information and by ruling out other possible causes, namely primary psychological diagnoses and organic causes (Meeusen et al). After ruling out other causes, history requires the following for diagnosis: worsened performance for at least two months even in the setting of appropriate rest, mood disturbance, and no other organic or psychological cause that could cause said symptoms. History should also look at possible triggers which can range from environmental exposures such as extreme heat or altitude, burnout with sport training, life stress, or insomnia among other possibilities. Nutritional history is also an important part of the evaluation.
In summary, overtraining syndrome is an entity that is not well understood and requires more research for a better understanding of its causation, pathophysiology, evaluation, and management. Recently studies have proposed using Fourier transform infrared spectroscopy as a possible way to predict changes in metabolism prior to development of symptoms; however, no clear data has been elucidated to date (Petbois et al). Other researchers such as Nederhof et al suggest psychomotor speed testing as a diagnostic test that could be utilized in the future, although, it too requires further evaluation as no clear utilization for this has been established (Nederhof et al). To date, history and ruling out other causes for symptoms remains the mainstay of diagnosis for overtraining syndrome and prevention or treatment with adequate rest post excessive exercise is the most useful management strategy to date (Meeusen et al).