Functional overreaching (FOR): intensified training results in a temporary decline in performance. When appropriate periods of recovery are provided, a positive “supercompensation” effect occurs, with the athlete exhibiting enhanced performance.
Nonfunctional overreaching (NFOR): an accumulation of training and/or nontraining stress resulting in short-term decrement in performance capacity with or without related physiological and psychological signs and symptoms of maladaptation in which restoration of performance capacity may take from several days to several weeks.
Overtraining syndrome (OTS): same as NFOR, except decrement is long-term and restoration takes several weeks or months.
Key point: the difference between NFOR and OTS is the amount of time needed for performance restoration; therefore, the diagnosis of OTS can often only be made retrospectively (3).
- Unknown, biochemical/hormonal hypotheses include the following: glycogen depletion, central fatigue/branched chain fatty acid depletion, glutamine depletion/immune dysfunction, autonomic imbalance, oxidative stress, hypothalamic dysregulation, and cytokine release/inflammation (1,2).
- The mechanism triggering these changes often involves a training error that results in imbalance between energy expenditure load and recovery. This typically occurs in combination with a complex set of psychological factors and environmental stressors (e.g., monotony of training, excessive competitions, sleep disturbances, interpersonal difficulties, academic/occupational stressors, illness, altitude exposure, heat or cold injury, etc.).
- Most commonly seen in endurance events such as swimming, cycling, or running
- Prevalence and incidence data for true OTS are lacking; the lifetime prevalence of NFOR/OTS is estimated to be approximately 30% for nonelite endurance athletes and 60% for elite athletes (2,3).
Important Differential Diagnoses
- NFOR/OTS is a diagnosis of exclusion (1).
- Common: caffeine withdrawal, environmental allergies, exercise-induced bronchospasm, infectious mononucleosis, insufficient sleep, anemia, performance anxiety, inadequate carbohydrate or protein intake, mood disorder, psychosocial stress, upper respiratory infection.
- Less common: dehydration, diabetes mellitus, eating disorder, hepatitis, hypothyroidism, lower respiratory infection, medication side effect (antidepressant, anxiolytic, antihistamine, β-blocker), post-concussive syndrome, pregnancy, substance abuse.
- Rare but important: adrenocortical insufficiency or excess, congenital or acquired heart disease, arrhythmia, bacterial endocarditis, congestive heart failure, coronary heart disease, human immunodeficiency virus, malabsorption syndrome, chronic lung disease, Lyme disease, malaria, malignancy, neuromuscular disorder, chronic renal disease, syphilis.
- Thorough history including chief complaint, training program, diet, medications, nutrition, illness, review of systems, and assessment of training goals.
- Hallmark feature in history: athletes with NFOR/OTS are usually able to start a normal training sequence or a race at their normal pace but are not able to complete the training load they are given or race as usual (3).
- Initial laboratory examinations: complete blood count, complete metabolic panel, Erythrocyte Sedimentation Rate/C-reactive protein, thyroid-stimulating hormone, iron studies, creatine kinase, urinalysis, and beta-human chorionic gonadotropin. Consider monospot, hepatitis panel, Lyme titer, toxicology screen, and chest x-ray.
- Prescribe absolute rest for 2 wk.
- ○ If mood is adversely affected with full rest, consider relative rest with well-defined expectations.
- If improved at follow-up, focus on adjustments to training and prevention (as follows).
- If no improvement, consider NFOR/OTS:
- ○ Will require prolonged training rest and further workup
- ○ Consider consulting with a sports psychologist and nutritionist.
- ○ Sequence of advancing activity should focus on frequency, then duration, then intensity (1,2).
- Monitor performance in time trials and standard exercise challenges.
- There are currently no good practical biomarkers for NFOR/OTS (2).
- Psychiatric indicators may be most useful. Examples include the Profile of Mood States and Recovery-Stress Questionnaire for Athletes (1).
- A two-bout maximal exercise protocol has shown differences in hypothalamic-pituitary-adrenal response for athletes with FOR, NFOR, and OTS and may have prognostic value (2).
Considerations for coaches, athletic trainers, and health care providers (2,3):
- Maintain accurate records of performance and encourage athletes to keep a diary of training load.
- Emphasize adequate rest and “time out” periods when performance declines, when an athlete complains of fatigue, or after illness or injury.
- Individualize and supervise training program.
- Avoid monotony of training.
- Encourage and reinforce optimal nutrition, hydration, and sleep.
- Be aware of life stressors, and communicate with athletes about physical, mental, and emotional concerns. Consider regular psychological questionnaires.
- Schedule regular health checks with a multidisciplinary team.
1. Gannon E, Howard TM. Overtraining syndrome. In: O’Connor FG, Casa DJ, Davis BA, St. Pierre P, Sallis RE, Wilder RP, editors. ACSM’s Sports Medicine: A Comprehensive Review
. Philadelphia (PA): Lippincott Williams & Wilkins; 2013. p. 265–8.
2. Kreher JB, Schwartz JB. Overtraining syndrome: a practical guide. Sports Health
. 2012; 4: 128–38.
3. Meeusen R, Duclos M, Foster C, et al. Prevention, diagnosis, and treatment of the overtraining syndrome: joint consensus statement of the European College of Sport Science and the American College of Sports Medicine. Med. Sci. Sports Exerc.
2013; 45: 186–205.