Overtraining syndrome

Autonomic imbalance hypothesis and overtraining syndrome

PURPOSE

The parasympathetic, Addison type, overtraining syndrome represents the dominant modern type of this syndrome. Beside additional mechanisms, an autonomic or neuroendocrine imbalance is hypothesized as underlying.

METHODS/RESULTS

Several findings support this thesis. During heavy endurance training or overreaching periods, the majority of findings give evidence of a reduced adrenal responsiveness to ACTH. This is compensated by an increased pituitary ACTH release. In an early stage of the overtraining syndrome, despite increased pituitary ACTH release, the decreased adrenal responsiveness is no longer compensated. The cortisol response decreases. In an advanced stage of overtraining syndrome, the pituitary ACTH release also decreases. In this stage, there is additionally evidence for decreased intrinsic sympathetic activity and sensitivity of target organs to catecholamines. This is indicated by decreased catecholamine excretion during night rest, decreased beta-adrenoreceptor density, decreased beta-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 at high caloric demands.

CONCLUSION

The described functional alterations of pituitary-adrenal axis and sympathetic system can explain persistent performance incompetence in affected athletes.

Overtraining and the BCAA hypothesis

The purpose of this review was to give an answer to the question whether there are convincing data to support the hypothesis of an amino acid imbalance as one possible mechanism to explain overtraining syndrome. Animal studies point to an enhanced synthesis of the neurotransmitter 5-hydroxytryptamine through an amino acid imbalance at the blood-brain barrier with a preferable tryptophan uptake into the brain, resulting in premature fatigue. Human studies, however, show contradictory results, mainly because of nonstandardized methodology, so that a final conclusion cannot be made at present. BCAA supplementation in addition to standard carbohydrate ingestion during sustained exercise seems to be of no eminent advantage to delay fatigue. The overall results concerning the BCAA hypothesis to explain overtraining are inconclusive and require more controlled experimental research.

Overtraining and recovery. A conceptual model

Fiercer competition between athletes and a wider knowledge of optimal training regimens dramatically influence current training methods. A single training bout per day was previously considered sufficient, whereas today athletes regularly train twice a day or more. Consequently, the number of athletes who are overtraining and have insufficient rest is increasing. Positive overtraining can be regarded as a natural process when the end result is adaptation and improved performance: the supercompensation principle--which includes the breakdown process (training) followed by the recovery process (rest)--is well known in sports. However, negative overtraining, causing maladaptation and other negative consequences such as staleness, can occur. Physiological, psychological, biochemical and immunological symptoms must be considered, both independently and together, to fully understand the 'staleness' syndrome. However, psychological testing may reveal early-warning signs more readily than the various physiological or immunological markers. The time frame of training and recovery is also important since the consequences of negative overtraining comprise an overtraining-response continuum from short to long term effects. An athlete failing to recover within 72 hours has presumably negatively overtrained and is in an overreached state. For an elite athlete to refrain from training for > 72 hours is extremely undesirable, highlighting the importance of a carefully monitored recovery process. There are many methods used to measure the training process but few with which to match the recovery process against it. One such framework for this is referred to as the total quality recovery (TQR) process. By using a TQR scale, structured around the scale developed for ratings of perceived exertion (RPE), the recovery process can be monitored and matched against the breakdown (training) process (TQR versus RPE). The TQR scale emphasises both the athlete's perception of recovery and the importance of active measures to improve the recovery process. Furthermore, directing attention to psychophysiological cues serves the same purpose as in RPE, i.e. increasing self-awareness. This article reviews and conceptualises the whole overtraining process. In doing so, it (i) aims to differentiate between the types of stress affecting an athlete's performance: (ii) identifies factors influencing an athlete's ability to adapt to physical training: (iii) structures the recovery process. The TQR method to facilitate monitoring of the recovery process is then suggested and a conceptual model that incorporates all of the important parameters for performance gain (adaptation) and loss (maladaptation).

Fatigue and underperformance in athletes: the overtraining syndrome

The overtraining syndrome affects mainly endurance athletes. It is a condition of chronic fatigue, underperformance, and an increased vulnerability to infection leading to recurrent infections. It is not yet known exactly how the stress of hard training and competition leads to the observed spectrum of symptoms. Psychological, endocrinogical, physiological, and immunological factors all play a role in the failure to recover from exercise. Careful monitoring of athletes and their response to training may help to prevent the overtraining syndrome. With a very careful exercise regimen and regeneration strategies, symptoms normally resolve in 6-12 weeks but may continue much longer or recur if athletes return to hard training too soon.

Resistance exercise overtraining and overreaching. Neuroendocrine responses

Overtraining is defined as an increase in training volume and/or intensity of exercise resulting in performance decrements. Recovery from this condition often requires many weeks or months. A shorter or less severe variation of overtraining is referred to as overreaching, which is easily recovered from in just a few days. Many structured training programmes utilise phases of overreaching to provide variety of the training stimulus. Much of the scientific literature on overtraining is based on aerobic activities, despite the fact that resistance exercise is a large component of many exercise programmes. Chronic resistance exercise can result in differential responses to overtraining depending on whether either training volume or training intensity is excessive. The neuroendocrine system is a complex physiological entity that can influence many other systems. Neuroendocrine responses to high volume resistance exercise overtraining appear to be somewhat similar to overtraining for aerobic activities. On the other hand, excessive resistance training intensity produces a distinctly different neuroendocrine profile. As a result, some of the neuroendocrine characteristics often suggested as markers of overtraining may not be applicable to some overtraining scenarios. Further research will permit elucidation of the interactions between the neuroendocrine system and other physiological systems in the aetiology of performance decrements from overtraining.

The emerging role of glutamine as an indicator of exercise stress and overtraining

Glutamine is an amino acid essential for many important homeostatic functions and for the optimal functioning of a number of tissues in the body, particularly the immune system and the gut. However, during various catabolic states, such as infection, surgery, trauma and acidosis, glutamine homeostasis is placed under stress, and glutamine reserves, particularly in the skeletal muscle, are depleted. With regard to glutamine metabolism, exercise stress may be viewed in a similar light to other catabolic stresses. Plasma glutamine responses to both prolonged and high intensity exercise are characterised by increased levels during exercise followed by significant decreases during the post-exercise recovery period, with several hours of recovery required for restoration of pre-exercise levels, depending on the intensity and duration of exercise. If recovery between exercise bouts is inadequate, the acute effects of exercise on plasma glutamine level may be cumulative, since overload training has been shown to result in low plasma glutamine levels requiring prolonged recovery. Athletes suffering from the overtraining syndrome (OTS) appear to maintain low plasma glutamine levels for months or years. All these observations have important implications for organ functions in these athletes, particularly with regard to the gut and the cells of the immune system, which may be adversely affected. In conclusion, if methodological issues are carefully considered, plasma glutamine level may be useful as an indicator of an overtrained state.

Cardiorespiratory, hormonal and haematological responses to submaximal cycling performed 2 days after eccentric or concentric exercise bouts

Eccentric muscle actions are known to induce delayed-onset muscle soreness (DOMS) and muscle weakness (reduced static strength and dynamic peak power output) that may persist for several days. The aim of the present study was to determine whether DOMS-inducing exercise affects physiological responses to subsequent submaximal dynamic exercise. Physiological and metabolic responses to a standardized exercise task were measured 2 days after the performance of an eccentric or concentric exercise bout. Six healthy, untrained male subjects aged 30 +/- 7 years (mean +/- S.D.) performed repeated eccentric contractions during 30 min of bench stepping (47-cm step, 15 steps min-1). On another occasion, they performed concentric contractions by walking uphill (8% incline) for 30 min at 5 km h-1, which elicited a similar heart rate response to bench stepping. Two days after the eccentric or concentric exercise, the subjects cycled for 15 min on an electrically braked cycle ergometer at a work rate (172 +/- 37 W) equivalent to 80% VO2 max. The order of the preceding treatments was randomized and the treatments were carried out 2 weeks apart. Two days after the eccentric exercise, all subjects reported leg muscle soreness and exhibited elevated levels of serum creatine kinase activity (P < 0.01) and plasma cortisol concentration (P < 0.05). After uphill walking, the subjects were not sore and serum creatine kinase activity was unchanged. Minute volume, breathing frequency, respiratory exchange ratio, heart rate, rating of perceived exertion, venous blood lactate concentration and plasma cortisol concentration were all higher (P < 0.05) during cycling after eccentric exercise compared with after uphill walking. Increases in plasma catecholamine concentrations and numbers of circulating leucocytes after cycling at 80% VO2 max for 15 min were similar under both experimental conditions, but the delayed leucocytosis (at 150 min post-exercise) was significantly greater (P < 0.01) for the post-eccentric exercise condition. We conclude that dynamic submaximal exercise performed 2 days following exercise with a large eccentric component produces physiological responses that are indicative of a higher relative exercise stress. It is likely that such effects will significantly limit the level and duration of exercise that can be achieved in subsequent training bouts over several days.

Overtraining: consequences and prevention

Overtraining refers to prolonged fatigue and reduced performance despite increased training. Its roots include muscle damage, cytokine actions, the acute phase response, improper nutrition, mood disturbances, and diverse consequences of stress hormone responses. The clinical features are varied, non-specific, anecdotal and legion. No single test is diagnostic. The best treatment is prevention, which means (1) balancing training and rest, (2) monitoring mood, fatigue, symptoms and performance, (3) reducing distress and (4) ensuring optimal nutrition, especially total energy and carbohydrate intake.

Equine pleuropneumonia

Pleuropneumonia is a clinically important equine disease, predisposed by a number of identifiable factors. Successful management is largely dependent on early identification and prompt initiation of appropriate treatment strategies. Rapid resolution of the disease process is associated with appropriate treatment commenced within 48 h of the causative insult. Lower airway contamination by oropharyngeal organisms and subsequent extension into the pulmonary parenchyma results in respiratory dysfunction and systemic toxaemia. Acute disease is associated with the isolation of facultatively anaerobic organisms, especially beta-haemolytic Streptococcus spp. and Pasteurellaceae. Delayed or inappropriate treatment is likely to result in chronic disease characterized by the involvement of anaerobic bacteria and a poor response to therapy. The primary mode of treatment for anaerobic infection of the human thorax is surgical drainage and resection of necrotic tissue but whilst such techniques have been described for the management of equine pleuropneumonia, the size of the equine thoracic cavity hinders accurate diagnostic evaluation and successful completion of such intervention. The chronic nature and cost of ongoing treatment and limitations on choice of antimicrobial agents warrant a poor prognosis for survival and a poorer prognosis for return to athletic endeavour.

Depression of plasma glutamine concentration after exercise stress and its possible influence on the immune system

OBJECTIVE

To determine whether plasma glutamine levels can be used as an indicator of exercise-induced stress, and to consider the possible effects of low plasma glutamine concentrations on the immune system.

METHODS

We used two exercise regimens: in Trial 1 seven male subjects were randomly stressed on a treadmill at 0, 30%, 60%, 90% and 120% of their maximal oxygen uptake (VO2max); in Trial 2 five highly trained male subjects underwent intensive interval training sessions twice daily for ten days, followed by a six-day recovery period.

RESULTS

Plasma glutamine concentrations decreased significantly from an average of 1244 +/- 121 mumol/L to 702 +/- 101 mumol/L after acute exercise at 90% VO2max (P < 0.05) and to 560 +/- 79 mumol/L at 120% VO2max (P < 0.001). Four of the five subjects showed reduced plasma glutamine concentrations by Day 6 of the overload training trial, with all subjects displaying significantly lower glutamine levels by Day 11. However, glutamine levels showed a variable rate of recovery over the six-day recovery period, with two subjects' levels remaining low by Day 16.

CONCLUSIONS

Reduced plasma glutamine concentrations may provide a good indication of severe exercise stress.

The haematological, biochemical and immunological profile of athletes suffering from the overtraining syndrome

To help clarify the overtraining syndrome (OTS), a combination of parameters were measured in ten athletes who were suffering from OTS. Blood samples were obtained at rest and a range of haematological, biochemical and immunological tests were carried out on the samples. For each parameter, the mean value for the group was compared to an established normal range amongst age-matched controls. The subjects were also asked to complete a questionnaire to establish the severity of their condition. The data indicated that the debilitating fatigue experienced by the OTS sufferers was not related to any of the blood parameters traditionally associated with chronic exercise stress, since levels were normal in OTS. The only parameter measured which deviated significantly from the normal range for both the sedentary controls and the athletes was the plasma concentration of glutamine. Although the data in this study would suggest that plasma glutamine concentrations represented an objective, measurable difference between OTS subjects and normal controls, it remains to be shown that there is any correlation between glutamine concentrations and other clinical symptoms of OTS such as physical capability.

Unaccustomed high mileage compared to intensity training-related neuromuscular excitability in distance runners

The influence of a 4-week unaccustomed average 103% mileage increase (ITV, increase in training volume; n = 8; average baseline mileage 85.9 km.week-1, final mileage 174.6 km.week-1) on performance and neuromuscular excitability (NME) was tested in experienced distance runners and controlled 1 year later by a 4-week unaccustomed average 152% increase in tempo-pace and interval-runs (ITI, increase in training intensity; n = 9; baseline 9 km.week-1 final 22.7 km.week-1) with an average total mileage of 61.7 km.week-1 (week 1) to 84.7 km.week-1 (week 4). Seven athletes participated in ITV as (week 4). Seven athletes participated in ITV as well as in ITI. During incremental treadmill test performance at a lactate concentration of 2 mmol.1-1 (2 LP) increased, and at 4 mmol.1-1 (4 LP) performance did not change, whereas total running distance (TD) during the incremental test decreased in ITV compared to an increase in 2 LP, 4 LP and TD during ITI which may indicate that there was an ITV-related overtraining. The NME of the reference muscles vastus medialis and rectus femoris deteriorated in ITV (day 28 compared to 0) compared to constant values during ITI, reflecting an ITV-related overload of neuromuscular structures.

Psychological and immunological correlates of acute overtraining

Five men undertook two intensive interval training sessions per day for 10 days, followed by 5 days of active recovery. Subjects supplied a venous blood sample and completed a mood-state questionnaire on days 1, 6, 11 and 16 of the study. Performance capabilities were assessed on days 1, 11 and 16 using a timed treadmill test to exhaustion at 18 kmh-1 and 1% grade. These individuals became acutely overtrained as indicated by significant reductions in running performance from day 1 to day 11. The overtrained state was accompanied by severe fatigue, immune system deficits, mood disturbance, physical complaints, sleep difficulties, and reduced appetite. Mood states moved toward baseline during recovery, but feelings of fatigue and immune system deficits persisted throughout the study.

A review of research in sports physiology

The physiology of sport encompasses a wide and diverse range of scientific interests. The intention, and major challenge of the review, is to collate the most pertinent of these interests into a coherent strategy for future research in sports physiology. The unifying concept of this review is the potential contribution of future research in sports physiology to the development of the elite competitor. The review promotes this theme through an indepth appraisal of current knowledge and identification of key areas of research that would most profitably advance the understanding and application of sports physiology. Central to this theme are the physiological limitations to exercise performance of the elite competitor and the adaptation of these physiological systems to further training, possibly leading to overtraining. Indeed, the potential to adapt to, or recover from, the ever increasing demands of training and competition is considered in sections on the development of strength and power, the child athlete and the limitations to performance in multiple sprint activities such as hockey and football. Throughout the review it is recognized that sports physiology is increasingly reliant upon advances in analytical techniques and quantitative measurement. Physiological measurement, the validity and accuracy of present and future procedures, and the correct interpretation of these data are therefore considered in detail in the final section of the review.

Endocrine and performance responses to high volume training and amino acid supplementation in elite junior weightlifters

To examine the effects of 1 week of high volume weightlifting and amino acid supplementation, 28 elite junior male weightlifters received either amino acid (protein) or lactose (placebo) capsules using double-blind procedures. Weightlifting test sessions were performed before and after 7 days of high volume training sessions. Serum concentrations of testosterone (Tes), cortisol (Cort), and growth hormone (GH) as well as whole blood lactate (HLa) were determined from blood draws. Lifting performance was not altered for either group after training, although vertical jump performance was not altered for either group after training, although vertical jump performance decreased for both groups. Both tests elicited significantly elevated exercise-induced hormonal and HLa concentrations. Significant decreases in postexercise hormonal and HLa concentrations from Test 1 to Test 2 were observed for both groups. Tes concentrations at 7 a.m. and preexercise decreased for both groups from Test 1 to Test 2, while the placebo group exhibited a decreased 7 a.m. Tes/Cort. These data suggest that amino acid supplementation does not influence resting or exercise-induced hormonal responses to 1 week of high volume weight training, but endocrine responses did suggest an impending over-training syndrome.

A review of overtraining syndrome-recognizing the signs and symptoms

Overtraining syndrome is common in athletes. It manifests itself with both physiological and psychological symptoms, and can adversely affect an athlete's performance. This article reviews the physiological and psychological signs and symptoms of overtraining syndrome in order to help the athletic trainer recognize the condition. With an understanding of overtraining syndrome, the athletic trainer can better aid coaches and athletes in preventing and treating this phenomenon, and thus maintain the athlete's optimal performance level.