Overtraining Syndrome
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Introduction[edit | edit source]
The purpose of training competitive athletes is to provide training loads that will improve performance. During this process, athletes can undergo various stages that may range from ‘undertraining’, during the period between competitive seasons or active rest and taper, to ‘overreaching’ (OR) and ‘overtraining’ (OT) which comprises maladaptations and diminished competitive performance.[1][2]When excessive training occurs concomitant with other stressors and inadequate recovery time, performance decrements will cause chronic maladaptations which can lead to the ‘Overtraining Syndrome’ (OTS).[3]
In the sports physiology, the overtraining syndrome is observed as the outcome of a training plan that is not balanced in the levels of exercise stress load, non-training (life) stress load, and rest period. The athlete proceeds from an appropriate training state to overreaching (OR) and eventually to the overtraining (OT) state if adjustments are not executed. Preventative management and early recognition are imperative to ensure the condition does not progress to a potentially serious and sport-ending stage.
Epidemiology[edit | edit source]
It is most commonly seen in endurance events like swimming, cycling, or running etc. Prevalence and incidence data for true OTS are lacking [4]; Prevalence of affected individuals at one time approaches 10% in elite collegiate endurance athletes (range 7-21%). The incidence of OTS in elite runners approaches 60% and even in non-elite competitive runners, nearly one third will experience OTS at some point during their running lifetime.[5] Outside of running, the incidence across all sports for high-level athletes is approximately 30-40%.[6]
Risk Factors[edit | edit source]
- Early single-sport specialization
- Significant increase in training load over a short period of time
- Training preparation for an important event
- Excessive parental and/or coach pressure to succeed
- Also, the risk of OTS has positively correlated with skill level as well as the prior incidence of OTS.[7]
Types of Overtraining Syndrome[edit | edit source]
Two types of OTS have been proposed:
- Hypoarousal form
- Hyperarousal form
Hypoarousal is also known as parasympathetic or Addison’s OTS. It is usually seen in endurance athletes (long-distance runners, rowers, cross-country skiers, cyclists, and swimmers). Hyperarousal is likewise called sympathetic or Basedow’s OTS. It is commonly seen in power athletes (sprinters, jumpers, and weight lifters) and occurs somewhat less frequently than the hypoarousal form.[8]
Difference between Overreaching (OR) and Overtraining (OT)[edit | edit source]
- Overreaching occurs from an accumulation of training and/or non-training stress leading to a short-term decrement in performance capacity with or without associated physiological and psychological signs of maladaptation (see table 1 below), during which restoration of performance can take up to several days to weeks.[9]
- Overtraining results from an increase in training and/or non-training stress leading to a long-term decrement in performance capacity with or without related physiological and psychological signs of maladaptation, in which restoration of performance can take up to several weeks or several months. Hence, OTS is a consequence of OT.[10] The syndrome is a continuum from training fatigue to overload and ultimately leading to full overtraining syndrome.
| Parasympathetic, Hypoarousal | Sympathetic, Hyperarousal |
|---|---|
| Decreased physical performance | Decreased physical performance |
| Easily fatigued or lethargic | Easily fatigued |
| Depression | Hyperexcitability |
| Normal or disturbed sleep | Disturbed sleep |
| Normal constant weight or weight loss | Weight loss |
| Low resting HR | Increased resting HR and BP |
| Hypoglycemia during exercise | slow recovery of HR and BP after exercise |
| Loss of competitive desire | Loss of competitive desire |
| Amenorrhea in women | Amenorrhea in women |
| Hypogonadism in men | Hypogonadism in men |
| Increased incidence of infections | Increased incidence of infections |
| Decreased maximal lactate response to exercise | Decreased maximal lactate response to exercise |
Table 1: Pathophysiologic Characteristics in Hypoarousal and Hyperarousal forms of Overtraining Syndrome
OR is practised by elite-level athletes and their coaches to improve sporting performance. These periods of intensified training may lead to a transient decline in performance capacity; however, when an appropriate recovery period is fulfilled a "Super Compensation" (the positively adaptive response of the body to physical stress) occurs and athletes performance is greatly enhanced compared to baseline. This short term, effective form of OR is termed as functional OR (FOR). But if FOR lasts for too long (that is for several weeks) [11]it becomes nonfunctional OR (NFOR), which becomes OT, and the athlete moves toward OTS.[1] These events and the progression can be compounded by inadequate nutrition, illness, and sleep disturbances.
So, the difference between these two training conditions is the amount of time required for the restoration of performance, and not the duration or the type of training stress or levels of physiological impairment.
Causes[edit | edit source]
There are plenty of theories but the Cytokine and Autonomic Dysfunction hypotheses are the most accepted and comprehensive in terms of identified symptoms and pathologies. These two theories overlap as Hypothalamic-pituitary-adrenal (HPA) axis dysfunction inevitably results in chronic inflammation.
Theories of OTS:[edit | edit source]
- Glycogen Hypothesis – Depleted glycogen stores are associated with fatigue and poor performance. Likely a contributing factor and linked with several genotypes and poor nutrition but does not explain the majority of associated pathologies.[5][4]
- Glutamine Hypothesis – Glutamine is necessary for immune cell function, DNA/RNA synthesis, nitrogen transport, gluconeogenesis and acid/base balance. Prolonged or repeated bouts of high-intensity exercise are associated with a reduction in plasma glutamine. Current evidence is inconclusive and shows only a weak relation with OTS. However, there is a possible role for glutamine supplementation.
- Oxidative Stress Hypothesis – Reactive oxygen species occur from exercise and cause inflammation, muscle fatigue and soreness. Higher levels are detected in overstrained athletes. It is not clear if this is a trigger or a result of OTS.[4]
- Cytokine Hypothesis – The repetitive micro-trauma occurring from strenuous exercise leads to the release of pro-inflammatory cytokines. Inadequate recovery and failed resolution of the inflammatory cascade results in a chronic, systemic inflammatory response involving increased levels of IL-1-alpha and TNF-alpha. This is an attractive hypothesis as it explains several hallmarks of OTS including reduced glycogen, low glutamine, reduced tryptophan/serotonin, decreased appetite, sleep disturbance and depression. It also explains altered immunity.[4][5]
- Autonomic Nervous System and HPA Hypothesis – Imbalance between the sympathetic/parasympathetic nervous system followed by alterations in HPA axis activity and feedback lead to numerous effects consistent with the exhaustion phase of Hans Selye’s adaptation theory.[4] Dysregulation in HPA feedback leads to persistent cortisol secretion and cortisol resistance (similar to insulin resistance), which results in extensive neurochemical, hormonal and immune abnormalities.[12]
Resources[edit | edit source]
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References[edit | edit source]
- ↑ 1.0 1.1 Meeusen R, Duclos M, Foster C, Fry A, Gleeson M, Nieman D, Raglin J, Rietjens G, Steinacker J, Urhausen A. Prevention, diagnosis and treatment of the overtraining syndrome: Joint consensus statement of the European College of Sport Science (ECSS) and the American College of Sports Medicine (ACSM). European Journal of Sport Science. 2013 Jan 1;13(1):1-24.
- ↑ Meeusen R, Duclos M, Gleeson M, Rietjens G, Steinacker J, Urhausen A. Prevention, diagnosis and treatment of the overtraining syndrome: ECSS position statement ‘task force’. European Journal of Sport Science. 2006 Mar 1;6(01):1-4.
- ↑ Cadegiani F. Overtraining Syndrome in Athletes: A Comprehensive Review and Novel Perspectives.
- ↑ 4.0 4.1 4.2 4.3 4.4 Kreher JB, Schwartz JB. Overtraining syndrome: a practical guide. Sports health. 2012 Mar;4(2):128-38.
- ↑ 5.0 5.1 5.2 Cardoos N. Overtraining syndrome. Current sports medicine reports. 2015 May 1;14(3):157-8.
- ↑ Raglin JS, Morgan WP. Development of a scale for use in monitoring training-induced distress in athletes. International journal of sports medicine. 1994 Feb;15(02):84-8.
- ↑ DiFiori JP, Benjamin HJ, Brenner JS, Gregory A, Jayanthi N, Landry GL, Luke A. Overuse injuries and burnout in youth sports: a position statement from the American Medical Society for Sports Medicine. British journal of sports medicine. 2014 Feb 1;48(4):287-8.
- ↑ Cadegiani F. Classical Understanding of Overtraining Syndrome. InOvertraining Syndrome in Athletes 2020 (pp. 9-23). Springer, Cham.
- ↑ Myrick KM. Overtraining and overreaching syndrome in athletes. The Journal for Nurse Practitioners. 2015 Nov 1;11(10):1018-22.
- ↑ Carfagno DG, Hendrix JC. Overtraining syndrome in the athlete: current clinical practice. Current sports medicine reports. 2014 Jan 1;13(1):45-51.
- ↑ Grandou C, Wallace L, Impellizzeri FM, Allen NG, Coutts AJ. Overtraining in resistance exercise: an exploratory systematic review and methodological appraisal of the literature. Sports Medicine. 2020 Apr;50(4):815-28.
- ↑ Cadegiani F. Introduction, Historical Perspective, and Basic Concepts on Overtraining Syndrome. InOvertraining Syndrome in Athletes 2020 (pp. 1-7). Springer, Cham.
