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Biochemical and Immunological Markers of Over-Training

J Sports Sci Med. 2002 Jun; 1(2): 31–41. Published online 2002 Jun 1., PMCID: PMC3963240

Michael Gleeson


Excessive training with insufficient recovery can led to a debilitating syndrome where performance and well-being can be affected for months.

Eliminating or minimizing this can be done by providing guidelines on:

  • Training  loads.

  • Recovery time.

  • Nutrition or pharmacological intervention.

  • Regular monitoring by using certain markers.

Practical markers would be those measured routinely in the lab.

To date, no single reliable objective marker of impending overtraining has been identified.

Some research does show promise and are based on findings that overtrained athletes appear to exhibit an altered hormonal response to stress. Examples:

1. A standardized bout or repeated bouts of high intensity exercise showed a lower i) heart rate, ii) blood lactate, and iii) plasma cortisol response.

2. Several immune measures obtained from a resting blood sample (e.g., the expression of specific cell surface proteins such as CD45RO+ on T-lymphocytes) may also reveal possible overtraining.

3. Other underperformance markers include i) post-viral fatigue, ii) glandular fever, iii) clinical depression, iv) poor diet, v) anemia, vi) asthma, vii) allergies, viii) thyroid disorders, ix) myocarditis and x) other medical problems that interfere with recovery.

Conclusions And a Suggested Battery of Tests for Monitoring Athletes at Risk of Overtraining

Possible measures that include those markers for which there is good scientific evidence of being reliable in detecting overtraining is shown here:

  • Performance

  • Mood state questionnaires.

  • Diary of responses to training (fatigue, muscle soreness) and symptoms of illness.

  • Sleeping heart rate.

  • Blood lactate and plasma Cortisol response to high intensity or incremental exercise.

  • Plasma creatine kinase activity.

  • Cortisol: Testosterone ratio.

  • Nocturnal urinary noradrenaline and adrenaline secretion.

  • Routine hematology (blood hemoglobin, serum ferritin, leukocyte counts)

  • T-lymphocyte CD4+/CD45RO+ expression.

Although further research is required, it seems that regular monitoring of the heart rate, plasma cortisol, and blood lactate response to excessive high intensity exercise could provide an objective and reliable means of identifying overtraining syndrome.

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