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School of Physiotherapy

Overtraining

Proposition for Debate - by Angela Peterson

Contents

Statement of the Topic

Overtraining

Introduction

In sports, performance results are dependant on maintaining an optimal balance between training and recovery. The traditionally accepted training principle is based on the idea that exercise results in a disturbance in cellular homeostasis, and these exercise induced changes are assumed to be the main stimulus for initiating the physiological responses that induce training adaptations by restoring cellular homeostasis. Although no strong evidence is available, it is assumed that the recovery processes do not stop when homeostasis is restored to original levels, but continue until a slight overcompensation is attained. The points at which recovery and overcompensation are complete are unknown, since no obtainable measurements of training are available to gain insight into the different components of the recovery process. This leads to possible errors in judgement regarding when it is appropriate to resume training following recovery periods. If insufficient recovery occurs over a long period of time, overtraining may result. This paper will attempt to define overtraining, identify the clinical features, aetiology and pathophysiology and discuss the methods of diagnosis and treatment.

Definition

Overtraining, also described as chronic fatigue, burnout and staleness has been defined as an imbalance between training/competition, versus recovery. Alternatively stated, it is too much training or competition combined with tool little time for regeneration.

Budgett (1998) defines the overtraining syndrome as a condition of fatigue and underperformance, often associated with frequent infections and depression that occurs following hard training and competition. The symptoms do not resolve despite two weeks of adequate rest, and there is no other identifiable medical cause.

The symptoms and consequences of overtraining have been reported to affect more than 60% of distance runners at least once during their career, 21% of athletes in the Australian swimming team during a half-year season, and more than 50% of semi-professional soccer players after a 4 month season.

Classification

Over-reaching

Overtraining is a syndrome that occurs on a fatigue continuum, with over-reaching at the lower end, and overtraining syndrome at the more severe end of the fatigue scale.

Short-term overtraining is called over-reaching, and can be seen as a normal part of athletic training or peaking for performance, and must be distinguished from long-term overtraining.

Over-reaching is usually encountered after several days of intense training and is generally associated with muscle fatigue. During the hard training or overload period, transient symptoms and signs may occur including changes in the profile of mood state (POMS) where tension, depression, anger, fatigue and confusion may be present. Other signs include depleted muscle glycogen stores, increased resting heart rate, increased testosterone:cortisol ratio, and increased creatine kinase levels indicating microscopic muscle damage if eccentric exercise has occurred. All these changes are normal physiological responses if recovery occurs within two weeks, and over-reaching is an important component of training for improved athletic performance.

Short-term over-reaching is thought to be associated with insufficient metabolic recovery resulting in a decline in ATP levels. When high intensity exercise is performed in a glycogen-depleted state, this may lead to an imbalance between ATP splitting and ATP regeneration. This early phase of overtraining is quickly reversible with sufficient recovery time to allow replenishment of the energy rich phosphate pool. Hence, over-reaching is thought to be related to insufficient metabolic recovery.

The remainder of this paper will discuss the long-term overtraining syndrome.

Overtraining

Some athletes are in a chronic state of insufficient recovery that occurs as a result of excessively prolonged and/or intense exercise, stressful competition or other stresses. Overtraining, or staleness is characterised by premature fatigue, decline in performance, mood changes, emotional instability and decreased motivation.

Systemic overtraining has been classified into a sympathetic and parasympathetic form. These are assumed to express different stages of overtraining. Although the pathophysiology of both forms of overtraining are poorly understood, it is thought that the sympathetic form is dominant in the early stages of overtraining, and in more advanced stages, the sympathetic system is inhibited resulting in marked dominance of the parasympathetic system.

Sympathetic

The sympathetic form of overtraining is characterised by increased sympathetic tone in the resting state. The symptoms include hyperexcitability, restlessness, and performance incompetence. It is most often observed in team sports, explosive, anaerobic events such as sprinting or secondary to additional significant non-training stress.

Parasympathetic

The parasympathetic form is characterised by domination of parasympathetic tone in the resting state as well as during exercise causing fatigue and apathy, and is most commonly seen in endurance athletes. It is the most common form of chronic overtraining syndrome and will be referred to from this point unless otherwise stated.

Clinical Features

Symptoms

The athletes' main complaint is underperformance , however increased susceptibility to infection, persistent high fatigue ratings, heavy muscles and depression are common symptoms. These are often ignored until performance is chronically affected. The athletes' reaction to underperformance is often an increase in training rather than rest, and this only serves to further exaggerate the recovery deficit.

Sleep disturbances, including difficulty in getting to sleep, nightmares, waking during the night and waking unrefreshed, are experienced by 90% of athletes suffering from overtraining syndrome.

Other symptoms include loss of appetite, weight loss, loss of competitive drive, increased emotional lability, anxiety and irritability , as well as mental exhaustion, poor attitude to training, injury and muscle soreness and joint pain.

Signs

Raised resting pulse rate, excessive sweating and upper respiratory tract infections or other minor infections are common signs. The infections tend to recur each time the athlete attempts to return to training and competition before they have fully recovered, resulting in recurrent cycles of infection. Cervical lymphadenopathy is reported to be a common finding in overtrained athletes. Other findings may include an increased postural fall in blood pressure and rise in postural heart rate.

Physiological testing may reveal reduced maximal oxygen uptake (VO2 max), reduced maximum power output and an increase in sub-maximum VO2 and heart rate, the heart rate taking a longer time than normal to return to the resting level following exercise.

Many of the other signs associated with overtraining are a result of the associated illness and as a result are variable and generally of little diagnostic value.

Aetiology

Training alone is seldom the primary cause of overtraining, rather it appears to be the total amount of stress on the athlete, which exceeds their capacity to cope. Additional non-training related stress factors that can lead to an increased risk of overtraining syndrome include social, educational, occupational, economical, nutritional, travel as well as monotony of training.

Training intensity or volume?

The sympathetic type of overtraining syndrome is assumed to be primarily the consequence of inappropriately intensive training sessions, however non-training related stress factors may play more of a role in the development of this type of overtraining syndrome, which has not been consistently identified by other authors.

The parasympathetic type of overtraining is assumed to be the consequence of an imbalance between long-term inappropriately high training volume in endurance sports, and too little time for regeneration, as well as non-training related stress factors. An increased risk of overtraining syndrome may be expected around 3 weeks of intensified and prolonged endurance training at a high training load level. Heavy training loads may be tolerated for extensive periods of time if athletes take a rest day every week and use alternating hard and easy days of training.

It has been suggested that intense interval training in which one to six minutes of hard exercise is repeated several times with a short rest is most likely to precipitate overtraining. There may also be a history of a sudden increase in training, prolonged heavy monotonous training, and commonly, additional non-training related stress. Regardless of the intensity or volume of training, most athletes will recover fully after two weeks of rest, which is built into the training programme using the principles of periodisation. This normally allows recovery and the full benefits of hard exercise. It is when the state of fatigue becomes so severe that recovery does not occur within two weeks that the diagnosis of overtraining is made.

Pathophysiology

There is a gradual transition from over-reaching to overtraining, and systemic overtraining is attributed to the failure of the hypothalamus to cope with the total amount of stress placed on the body. The hypothalamus is responsible for integration and control of the endocrine and autonomic nervous system, enabling the body to cope with the stresses placed upon it. The regulatory response from the hypothalamus can be expressed via the endocrine system, the autonomic nervous system and behaviour.

Endocrine

Recovery is initiated by the disturbance in homeostasis, however there is evidence that the recovery processes are modulated by the endocrine system, the resulting hormonal response enabling modification and amplification of the recovery and adaptation processes.

Studies investigating the hormonal response in overtraining show widely conflicting results. The most commonly reported findings are discussed below.

Early studies found a reduced response of the stressor hormones gonadotrophin hormone (GH), ACTH and cortisol, to insulin-induced hypoglycaemia in overtrained athletes. In a study conducted on swimmers, higher nor-adrenaline levels were found during the tapering phase, the levels generally proportional to training stress. Higher nor-adrenaline levels and the fall in basal nocturnal plasma dopamine, and adrenaline levels have been shown to correlate well with symptoms of overtraining, and have therefore been proposed as methods of monitoring overtraining. The role of hormones in the overtraining syndrome remains poorly understood.

Increased salivary cortisol levels and lowered testosterone:cortisol ratio are other reported findings in overtrained athletes , however other authors have not been able to confirm this finding, with progressively lower testosterone:cortisol ratios also reported in over-reaching states. It is thought that workout-related increases in stress hormones may suppress the hypothalamic-pituitary-adrenal-testicular axis (the male equivalent of female amenorrhea), resulting in reduced ratios in endurance athletes.

While there is no literary consensus on the hormonal response associated with overtraining, the clinical features of the syndrome, including changes in mood state, recovery rate, reproductive state and sleep disturbances, are reported to be consistent with maladaptation in certain parts of the brain with consequent changes in hypothalamic effector output.

Autonomic Imbalance Theory

Clinically, it has been suggested that prolonged training produces an autonomic imbalance. During heavy endurance training or over-reaching periods, there is evidence of reduced adrenal responsiveness to ACTH. This is compensated by an increased pituitary ACTH release. In the early stages of the overtraining syndrome, despite increased pituitary ACTH release, the decreased adrenal responsiveness is no longer compensated and the cortisol response decreases. In an advanced stage of overtraining syndrome, the pituitary ACTH release also decreases. In this stage there is additional evidence for decreased intrinsic sympathetic activity and sensitivity of target organs to catecholamines. Plasma levels and urinary excretion of free catecholamines are indicators of the sympathetic nervous systems' activity and decreased sensitivity is indicated by decreased catecholamine excretion during night rest, decreased ß-adrenoreceptor density, decreased ß-adrenoreceptor-mediated responses and increased resting plasma norepinephrine levels and responses to exercise. However this complete pattern is only observed subsequent to high-volume endurance overtraining.

Hooper (1995), recounts 2 case studies, one of a middle-distance runner who showed markedly elevated catecholamine excretion during the weeks prior to the 1984 Olympic Games, for which he qualified, but later withdrew for non-training related stress and personal reasons. Other key findings during this period included restlessness, hyperexcitability and performance incompetence. The second case involved a tennis professional who presented with burnout syndrome and showed low catecholamine excretion levels within the range normally only observed in patients suffering from sympathetic insufficiency.

Another study had previously found that performance incompetence was correlated with a significant decrease in basal catecholamine excretion and also with athlete complaint rating. However, the marked decrease seen was a late finding, and was not found to be an early indicator of overtraining syndrome.

In view of these results, it was postulated that the parasympathetic type of overtraining syndrome results in a decrease in sympathetic activity that may explain fatigue originating in the brain (central fatigue).

Central Fatigue

Central fatigue has been postulated as another physiological mechanism of overtraining. A study on Olympic overtrained athletes found reduced peak power output using a 20 second Wingate Bike test, and weaker isometric and concentric quadriceps contraction compared to controls. However, a rise in isometric power was produced by tetanic stimulation of the quadriceps muscle. The authors suggest this indicates a failure to maximally activate fast twitch muscle fibres and is consistent with the common report from athletes, where at the end of the race, they "step on the gas, but there's nothing there".

The amino acid theory is another possible physiological explanation for central fatigue. In a study on rats, the amino acid tryptophan was shown to be converted to the neurotransmitter 5-hydroxytryptamine (5-HT) in the brain. The neurotransmitter 5-HT is important in tiredness and sleep. Tryptophan competes with other branched chain amino acids for entry into the brain on the same amino acid carrier. Increased utilisation of branched chain amino acids by exercising muscle in the presence of low muscle glycogen, results in decreased blood amino acid levels, increasing the ratio of tryptophan:amino acids, and resultant preferential entry of tryptophan into the brain. In endurance exercise, there is a rise in fatty acids and a decrease in amino acids and it was suggested that the increase in 5-HT may account for many of the features of overtraining, including sleep disturbance, central fatigue, loss of appetite, and inhibition of release of factors which control pituitary hormones from the hypothalamus. This study was, however conducted on rats, and human studies have not confirmed these results, mainly due to methodological differences.

Immunosuppression

There is evidence to show that intense, heavy exercise increases the incidence of infection. A correlation has been shown between the rate of upper respiratory tract infections and the level of fitness of the athlete, degree of intensity of exercise , higher training mileage, and following marathon runs. Factors reported to be associated with this finding include raised cortisol levels, reduced salivary immunoglobulin levels, and low glutamine levels.

A study by Gleeson et al (1999) found that immunosuppression, as measured by lowered salivary immunoglobulin (IgA) levels in a group of elite swimmers, was shown to be predictive of risk of infection when measured over the period of a swimming season. The same was found in their moderately exercising control subjects. Their results indicated that the lower the level of salivary IgA, the higher the risk of infection and suggest that athletes with preseason salivary IgA levels below 40mg/L may be at risk. They found that the rate of decline in levels over the season was also predictive. These authors report that secretory IgA plays a major role in immune protection at mucosal surfaces by providing specific antibodies in response to pathogens, and a lack of, or inability to produce specific IgA antibodies can lead to increased risk of infection.

Glutamine in an essential amino acid for rapidly dividing cells such as lymphocytes, and was found to be deficient in overtrained athletes, and significantly reduced following hard training efforts. It has been suggested that low plasma glutamine levels associated with intense training and overtraining may compromise lymphocyte function and that this may be related to an increased incidence of infection.

Diagnosis: Markers of Excessive Exercise

Because the transition from over-reaching to overtraining is a gradual one, and symptoms are highly variable, no clear diagnostic criteria are available for overtraining syndrome. Athletes will tolerate differing amounts of training, competition and stress at different times depending on their level of fitness and general health during the season. In practice it is difficult to distinguish overtraining from over-reaching.

Many attempts have been made to detect over-reaching and overtraining in the earliest stage. Tests such as time to volitional fatigue on a cycle ergometer at 110% of anaerobic threshold, salivary IgA levels, plasma glutamine levels and psychological assessment tools are currently the most promising methods for detecting overtraining. Several factors including ethical issues of inducing overtraining in an elite athlete, and the absence of human generalisability from animal models present consistent research limitations.

Psychological Markers

Overtraining has been reported to involve a complex interaction of psychological stresses including individual cognitive, behavioural and emotional characteristics, as well as the skills of the athlete, environmental and social stresses.

The most promising tool for identifying the overtrained state, is reported to be the psychological mood state, and several validated tools have been used for this purpose. American collegiate swimmers were studied using the profile of mood state (POMS) questionnaire. When the mood state improved, training was increased, and when the mood state deteriorated, training was decreased. Using this method, the rate of overtraining was reduced from 10% to zero. They determined that the mood state was significant if it does not improve during tapering in the lead up to competition. Unfortunately, at this late stage, it may be too late for intervention and reversal of the syndrome. The recommendation from this study was that tapering and recovery is best performed throughout the season to enable regular monitoring of recovery.

Immunological Markers

Salivary IgA levels may be a useful immunological marker of excessive exercise, and further research is needed to determine the validity of plasma glutamine levels as a blood marker.

Physiological Markers

A recent study found that a cycle ergometer test performed at an intensity of 110% of the athletes' anaerobic threshold resulted in a 27% decrease in time to exhaustion in the overtrained state, when other laboratory variables could not detect a difference between well trained and overtrained athletes.

Many athletes monitor their heart rate, and while this is a non-specific, it can indicate when there is a change in the physiological state. There remains a lack of consensus in the literature on the usefulness of heart rate and blood pressure measures in monitoring the training of endurance athletes.

Biological Markers

Haematological, biochemical, hormonal and immunological markers have been extensively studied. The difficulties in these studies, lie in that many of these variables change with acute and chronic exercise, and their relationship to the overtrained state has not been clearly identified. No single biological parameter has been identified as a reliable marker of excessive exercise.

McKenzie (1999) states that the pattern of change in these various markers in the overtraining athlete involves firstly a change in the psychological markers, followed by medical condition then performance. It appears that this monitoring method has been used effectively to follow athletes, and has allowed intervention to prevent full-blown overtraining.

Differential Diagnosis

There is no diagnostic test available to detect overtraining, therefore it is important to screen the athlete to exclude other causes of chronic fatigue. This may involve simply a routine haematological screening test. It is important to note that athletic anaemia is a common physiological finding. It is due to haemodilution and does not affect performance. Recurrent upper respiratory tract infections may be indicative of allergic rhinitis or exercise-induced asthma. Important differential diagnoses include viral myocarditis, cardiac arrhythmia and post-viral illness.

Treatment

An holistic approach to the treatment of overtraining is essential, since evidence shows it has more than a purely physiological cause.

Physiological recovery is an important aspect in the treatment of overtraining syndrome. Athletes will not comply when instructed to rest. Low-level exercise has been shown to speed the recovery from overtraining syndrome. Therefore, it has been suggested that in the initial phase of recovery, aerobic exercise at heart rates of 120-140 beats per minute for 5-10 minutes each day be prescribed, and this can be slowly built up over the period of 6-12 weeks. The emphasis is increasing volume rather than intensity, and volume should be increased gradually up to one hour per day. Once this is volume is reached, intensity can be gradually increased above the lactate threshold. Interruption of the cycle of partial recovery following hard training, resulting in cumulative breakdown is required and care must be taken when increasing intensity, to allow recovery following the harder sessions. It is recommended that athletes recover completely at least once per week. Cross training is recommended to reduce the temptation to increase training too rapidly in the athletes' own sport.

Periodisation of training parameters plays an important role in the prevention of overtraining. Many training programmes are designed to alternate hard and light training days within the normal training programme. Training intensity and the intervals between training sessions have been reported to be the most important factors in optimising performance and reducing the risk of overtraining.

Prevention

Prevention is the best treatment for overtraining, and because exercise tolerance shows high inter and intra-individual variability, each athlete must be monitored and the training load adjusted according to individual requirements. The maintenance of a training diary can be of use in monitoring training intensity and volume as well as mood, fatigue, symptoms and performance. This serves to ensure a balance between training and rest, and identify early signs of psychological or performance changes. Other strategies reported to be of use in the prevention of overtraining syndrome include a reducing distress, optimal diet including total energy and carbohydrate intake and full hydration.

Regeneration strategies are used widely in Eastern Block countries , however no trials were found testing these strategies. They are reported to include rest, relaxation, massage, hydrotherapy, nutritional analysis, counselling and psychotherapy.

Environmental and social stressors must be addressed, and concurrent illness may be treated medically.

Clinical Implications

The progression of short-term over-reaching to overtraining is a gradual one, and can easily go unrecognised until chronic under-performance becomes evident. Monitoring of the athletes' psychological profile, training methods, and performance by means of a training diary are required and will enable early detection of overtraining. The volume of training and subsequent rest periods, are of particular interest. As a physiotherapist, overtraining may be suspected with presentation for treatment of recurrent, overuse injuries, where the athlete may be in a chronic form of acute injury response.

Often, patients confide physiotherapists who they see regularly, and identification of significant non-training related stress factors is important. Recurrent upper respiratory tract, or other minor infections should also alert the medical personnel to the possibility of overtraining.

Physiological adaptation requires overload balanced with adequate recovery. An increased risk of overtraining syndrome may be expected around 3 weeks of intensified and prolonged endurance training at a high training load level. Heavy training loads may be tolerated for extensive periods of time if athletes take a rest day every week and use alternating hard and easy days of training.

Travel schedules must also be structured to allow adjustment to different time zones, and allow sufficient rest and recovery time while on tour. Coaches need to be educated while on tour and in tournament situations regarding duration and intensity of additional training sessions and adequate rest and recovery times. Management need to be made aware of the nutritional issues facing touring athletes who are away from their normal dietary routine and ensure that the food provided has high energy, particularly carbohydrate content.

In the event of overtraining, the athlete must be educated, and reassured that less training rather than more, is the only way to improve their performance, and that it could take up to 12 weeks. Significantly less training is required, and the volume must be gradually increased to one hour of aerobic work prior to increasing the intensity. Cross training is recommended to avoid temptation of the athlete to over-train in their familiar sport.

Conclusion

Overtraining is a syndrome affecting mainly endurance athletes, characterised by chronic fatigue and under-performance, and increased susceptibility to infection. It is the result of either too much training or too little recovery or a combination of both. It remains unclear how the stress of hard training and competition result in these signs and symptoms, however dysfunction of the hypothalamus from repeated stress of a physical or non-physical nature is the most widely accepted explanation. Factors including psychological, endocrinological, physiological and immunological are reported to be responsible for the observed signs and symptoms, all resulting in a failure to recover adequately from exercise. Careful monitoring of the athletes' response to training may help prevent, or at least recognise the early signs of overtraining. Treatment should involve 6-12 weeks of a carefully controlled exercise regimen initially increasing aerobic training volume, and then intensity, with care taken to allow sufficient recovery following hard training sessions and one bout of full recovery every week.

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Exercise Physiology Educational Resources 2000