Understanding Overtraining: Causes and Diagnostic Theories

To start, it would be useful to define the levels of training stressors in terms of their impact on adaptation as it will dovetail into our definition of overtraining:

· Level 1: Undertraining

Indicating a suboptimal training stimulus in which adaptations are negligible or reduced.

· Level 2: Acute overload

The standard output that is typically observed in a training session where exercise leads to positive adaptations.

· Level 3: Overreaching

Best understood as high-intensity training, the days in the gym where one pushes themselves to the max and try to surpass a previous best.

· Level 4: Chronic Overreaching

When someone consistently pushes themselves to their limit in the gym without adequate rest, that overtraining takes place.

Overtraining can thus be defined as the point in training when adaptations reach the point of diminishing returns. Characterized by disruptions to the immune system, hormone system, and, the way your nerves and muscles work together (neuromuscular), and mood regulation (informed by Kreher, 2012).

Symptoms for Overtraining Syndrome (OTS) relate specifically to;

Sympathetic (high-intensity)
Parasympathetic (low-intensity)

Symptoms of Resistance/Strength Overtraining Include

o Irritability

o Agitation

o Tachycardia

o Hypertension

o Restlessness; the symptoms for endurance overtraining fatigue, depression, bradycardia, and loss of motivation (Kreher, 2012).

With these symptoms presented, we can now delve into theories about the underlying physiological mechanisms of overtraining.

The Cytokine Hypothesis

The most likely and most comprehensive explanation for the underlying mechanism of overtraining syndrome.

The theory is based on two facts:

- That we experience post-exercise inflammation as a result of cytokines (proteins that regulate our immune response) and

- That cytokine levels increase to even greater extent as a result of overtraining.

-The theory; the hypothalamic center (part of brain that controls basic bodily functions and mood through hormonal release) that regulates mood in response to illness is also influenced by cytokines meaning that an increase in cytokine levels (as a result of overtraining) can over-regulate the hypothalamus and thus cause the mood disruptions seen in OTS.

-The cytokine theory also incorporates the glycogen hypothesis which suggests that low glycogen levels as seen in overtrained individuals can be correlated to fatigue and diminished performance, by which the cytokine theory adds that not only do increased cytokines decrease glucose transport to muscles thereby causing fatigue but that increased cytokines stimulate the release of cortisol and other glucose-regulator hormones, redoubling the rate of glucose metabolism leading to prolonged fatigue (Chung et al., 2021).

References

- Kreher, J. B., & Schwartz, J. B. (2012). Overtraining syndrome: a practical guide. Sports health, 4(2), 128–138. https://doi.org/10.1177/1941738111434406

- Chung, Y., Hsiao, Y. T., & Huang, W. C. (2021). Physiological and psychological effects of treadmill overtraining implementation. Biology, 10(6), 515. https://doi.org/10.3390/biology10060515