- 1 Introduction
- 2 Epidemiology
- 3 Types of Overtraining Syndrome
- 4 Difference Between Overreaching and Overtraining
- 5 Stages of Overtraining Syndrome
- 6 Aetiology
- 7 Risk Factors
- 8 Clinical Presentation
- 9 Diagnostic Tests
- 10 Treatment
- 11 Prevention
- 12 References
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. When excessive training occurs concomitant with other stressors and inadequate recovery time, performance decrements will cause chronic maladaptations which can lead to ‘Overtraining Syndrome’ (OTS) also called Paradoxical Deconditioning Syndrome (PDS).
In 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.
It is most commonly seen in endurance events like swimming, cycling, or running etc. Prevalence and incidence data for true OTS are lacking ; Prevalence of affected individuals at one time approaches 10% in elite collegiate endurance athletes (range 7-21%). The incidence of overtraining syndrome 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. Outside of running, the incidence across all sports for high-level athletes is approximately 30-40%.
Types of Overtraining Syndrome
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.
Difference Between Overreaching and Overtraining
- Overreaching (OR) 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. Overreaching (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.
- Overtraining (OT) 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. The syndrome is a continuum from training fatigue to overload and ultimately leading to full overtraining syndrome.
This short term, effective form of overreaching (OR) is termed as functional OR (FOR). But if FOR lasts for too long (that is for several weeks)  it becomes nonfunctional OR (NFOR), which becomes OT, and the athlete moves toward OTS. 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.
|Parasympathetic, Hypoarousal||Sympathetic, Hyperarousal|
|Decreased physical performance||Decreased physical performance|
|Easily fatigued or lethargic||Easily fatigued|
|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
Stages of Overtraining Syndrome
The overtraining syndrome can occur in three different stages:
- Stage 1: Also called Functional Overtraining. The early-stage where very subtle signs and symptoms can indicate an athlete is starting to overtrain.
- Stage 2: Also termed as Sympathetic Overtraining. A more obvious stage linked with specific nervous, hormonal and mechanical imbalances causing different signs and symptoms.
- Stage 3: Also termed as Parasympathetic Overtraining. A serious end-stage of overtraining linked with the exhaustion of nervous and hormonal factors.
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
- 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.
- 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 overtraining syndrome.
- 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.
- 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. 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.
- 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 overtraining syndrome.
One of the most important challenges in overtraining syndrome is early recognization. Once established, treatment becomes much harder and prolonged. Diagnosis relies on various areas of evaluation.
When taking a history look for potential triggers:
- Increased training load without adequate rest
- Training monotony
- Multiple competitions
- Sleep abnormalities
- Additional stressors – personal, work etc.
- Recent illness or injuries
- Environmental exposure – altitude, heat, cold
Rule Out Organic Disease
- Several organic diseases can present in a similar way to overtraining syndrome and are often overlooked as the population tends to be younger and disease uncommon.
- Undiagnosed lung disease (asthma)
- Hormonal Disease (Thyroid, Diabetes)
- Infection (hepatitis, HIV, myocarditis, Lyme, EBV)
- Malnutrition/Eating Disorders (RED-S or Relative Energy Deficiency Sport) is a low-energy state resulting from inadequate nutrition relative to the degree of training. Originally recognized as the Female Athlete Triad (anorexia, amenorrhoea, osteoporosis) it is presently known to affect both men and women equally. Although alike in presentation, it can be distinguished from the overtraining syndrome. RED-S is predominantly a low-energy rather than a low-performance state; there are stronger food anxiety and body image concerns; bone injury (stress fractures) occurs rather than muscle injury; RED-S is quickly reversed with appropriate nutrition.
Signs and Symptoms
Symptoms are quite variable among individuals and may occur in any order. However, even one or two can indicate early OTS and should not be ignored. The more symptoms there are the more advanced the condition.
- Inability to complete a training session
- Tired but unable to sleep
- Loss of “finishing kick”
- Increased irritability
- Depressed mood/Enhanced PMS
- Weight loss/Weight Gain
- Persistent thirst
- Recurrent colds
- These findings are quite variable between individuals. A high resting heart rate (10-30 bpm above normal range) is the most reliable and usually occurs in the early stages of OTS:
- Increased resting heart rate
- Increased fatigued/Sickly appearance
- Muscle tenderness/tightness
- Vague muscle and/or joint pain
- Weak hair/nails
A variety of measurement tools have been developed to correctly monitor the training load and quantify the recovery rate. An important characteristic of these measurement tools is that they should be easy to administer, non-invasive and sensitive to change.
Ratings of perceived exertion scale is a valuable determinant of impending fatigue during exercise testing and are universally accepted as a useful tool for prescribing aerobic exercise intensity. One study introduced the concept of session ratings of perceived exertion (sRPE), in which an athlete subjectively estimates the overall complexity of a whole workout after its completion. Ideally, weekly RPE totals must change to ensure varied intensity. Also, monitoring the RPE for a specific workout allows performance and fatigue to be followed. If a certain routine is rated a 6 at the beginning of the season but becomes an 8 halfway through, then the athlete may be showing signs of the paradoxical deconditioning syndrome (PDS).
The measurement of recovery heart rate has also been recommended as a valuable tool. A study showed that the chosen exercise intensity of a sub-maximal test must elicit a heart rate of between 85 to 90% of HRmax because the lowest day-to-day variations were found at this intensity. From test to test a change in heart rate recovery of >6 bpm or a change in sub-maximal heart rate of >3 bpm can be marked as a significant change under controlled conditions. These changes can be caused by an improved/decreased training status or the accumulation of fatigue as a result of functional overreaching (FOR).
- Physical and Mental testing seems to be the most reliable and helpful method of assessing impending or established OTS. These tests include time-to fatigue tests, sport-specific maximum aerobic function tests, and strength or power tests for particular sports.
- A research study showed that the use of the two maximal incremental exercise tests separated by 4 hours can be helpful tools to assess the performance decrements usually observed in OTS athletes. A reduction in exercise time of at least 10% is required to be significant. Furthermore, this decrease in performance needs to be validated by specific changes in hormone concentrations.
- The Profile of Mood State questionnaire (or POMS) is a simple and easy test with good reliability in confirming the diagnosis of OTS. By assigning values to self-perceived issues covering components like fatigue, vigour, tension, anger, confusion, depression, and overall emotional state score can be documented and monitored.
- Other tests include the Multi-Component Training Distress Scale (MTDS), and Recovery-Stress Questionnaire for Athletes (REST-Q) assessments, etc. They consolidate both mental and physical self-assessments of stress and recovery. The REST-Q questionnaire is more accessible and is available in a general version as well as specific versions for athletes.
- Psychomotor speed tests are becoming increasingly beneficial. They are simple, non-invasive, and readily available. They seem to have high validity in evaluating athletic performance, combining mental and motor skills. Examples comprise Zig-zag tracking, the Gibson Spiral Maze, and the STROOP test.
Blood tests that have been used to diagnose OTS include blood sugar levels (frequently elevated due to the mild insulin resistance that occurs in few individuals), lactate, Glutamine, cortisol but are invasive, hard to interpret, and often unreliable. Each hormone has a pre-defined exercise-induced pattern. When investigating hormonal markers of training adaptation it is very important to focus on particular hormones for their informational potential and synchronize their sampling in accordance with their response patterns. However, testing of central hypothalamic/pituitary regulation needs functional tests that are considered invasive and require diagnostic expertise and these tests are time-consuming and expensive. Although, there is no one biomarker for OTS, there are promising biomarkers that remain in the field of investigation and research. Due to the oxidative stress of excessive exercise, many have studied the redox status of athletes. Oxidative stress biomarkers like reduced oxidized glutathione ratio and urinary isoprostanes are promising for scaling training load and overreached status.
Once an athlete presents with signs of OTS then treatment needs to be initiated promptly and thoroughly in order to be effective. Ignoring signs or taking half-measures will result in further deterioration and will take a longer time for recovery.
No treatment is required for stage 1 OTS other than adjusting overload training with the appropriate recovery period. This often provides improvements in symptoms and even training within one to four weeks. This rapid progress will be demonstrated in the Maximum Aerobic Function (MAF) test  or other evaluations, including reductions in injuries and mental states. MAF test consists of measuring an athlete’s workout while maintaining a sub-maximal heart rate. (The sub-max heart rate corresponds with low- to moderate-intensity training using the "MAF 180 Formula". This enables athletes to find the ideal maximum aerobic heart rate in which to base all aerobic training. When overdone, this number shows a rapid transition towards anaerobic work. A typical issue in Stage 1 overtraining is the imbalance between aerobic and anaerobic capacity. While this can be determined by several tests, it is not difficult to compare maximum aerobic function versus maximum anaerobic function. Aerobic capacity can be determined with the MAF Test, while anaerobic function by competitive performance. An imbalance is quite evident, for instance, if you can perform the MAF Test at 7 minutes per mile but run a 5 or 10K race under 5 minutes per mile. It is not uncommon for skilled athletes in Stage 1 (or the start of Stage 2) to compete at high levels but has a poor aerobic function. (Reduced performance levels can not be evident until the middle and later stages of overtraining syndrome).
Treatment of nonfunctional overreaching (NFO) and OTS is relative rest. It is suggested to build up volume prior to intensity, starting from 5-10 minutes daily until 1 hour is tolerated. It is unclear which strategy is the best, so the motivation for exercise, internal versus external factors should be taken into consideration when recommending complete versus relative rest. Allowing cross-training may overcome some of the inevitable despondency resulting from a halted season. Restoring sleep is one of the most vital factors in healing as well as improve nutrition ad hydration. This is often difficult for an athlete to accept so involving a sports psychologist can be beneficial.
Reduction in activity and training needs to be quite profound and surprises most athletes. However, failure to adhere to a proper rest and recovery protocol will result in a high likelihood of relapse. Recommended time frames differ according to the stage of OTS and are shown in Table 2 below. However, in Stage 1, participation in competition does not have to stop, the frequency of events should undoubtedly be minimized.
|Stage 1||Stage 2||Stage 3|
|Reduce Training 50-70%||Yes||Yes||Yes|
|Eliminate High Intensity||Yes||Yes||Yes|
|Recovery time||1-4 weeks||4-12 weeks||12-52 weeks|
Table 2: Treatment protocol for the stages of OTS.
Major components of the prevention of OTS are regular screening and education. One should educate athletes about the risk for overtraining which is the initial signs of overreaching that can be identified by an increased rating of perceived exertion for a given workload. There are no evidence-based means of preventing PDS/ OTS. However, observation of training load, performance measures, and mood questionnaires can be helpful to interrupt the progression from functional overreaching (FO) to nonfunctional overreaching (NFO) and finally to OTS. Research has shown a decrease in “burnout” in swimmers from 10% to zero when adjusting the training load in response to the Profile of Mood States questionnaire. They found when the mood state was decreased, the training load was also decreased.
Major components of prevention are screening and education. One should educate athletes at risk for overtraining that one of the initial signs of overreaching is an increased rating of perceived exertion for a given workload.
The most frequently used methods to monitor training and prevent overtraining syndrome are:
- Retrospective Questionnaires
- Training diaries: It is useful for detecting not only slight differences in training load but also the subjective parameters like muscle soreness, mental and physical well being. Modify training volume and intensity based on performance and mood. Ensure adequate carbohydrate ingestion during exercise and keep a rest period of >6 hours between exercise bouts.
- Physiological screening
- The direct observational method
- The MAF Test can be the most powerful and helpful tool for evaluating overtraining in the earliest stage and can give the first objective sign, even prior to symptoms. This test should be conducted every four weeks for the early detection of OTS.
- Early identification and treatment of adrenal dysfunction are important for the prevention of overtraining (and is easily done with regular salivary testing).
- Psychological screening  of athletes and the ratings of perceived exertion  have received more and more recognition recently.
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