| Staying On Track
Recognition of Overtraining Syndrome in Endurance Athletics Originally Published in Techniques Magazine
Definitions A description of successful training is the introduction of a stimulus that causes a disturbance in the body's homeostasis, followed by a period of regeneration and adaptation to that exercise. Therefore, it is not the stimulus that supplies the improvement in performance but the stimulus followed by a period for regeneration. Successful training must involve overload but also must avoid the combination of excessive overload with inadequate recovery (16). The phases of training are often viewed as a continuum and range from undertraining, the period between competitive seasons or during active rest to overtraining which results in various maladaptations, a decrease in work capacity, and performance (1,7,16). There is a lack of consistent terminology in the study of overtraining, and for this reason, it is important to clarify the vocabulary used throughout the rest of this article. This terminology is based from work by Halson and Jeukendrup and compiled by Meeusen et al. Overtraining (OT) is an accumulation of training and/or non-training stress resulting in long-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 several weeks or months (7,16). Overreaching (OR) is an accumulation of training and/or non-training 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 (7,16). It should be noted that OT and OR are considered the process (the "verbs") and the following are definitions of the outcomes: Functional Overreaching (FOR) occurs when OR is employed by an athlete who intensifies training and undergoes a temporary performance decrement followed by improved performance. This is in contrast to Non-Functional Overreaching (NFOR), which leads to a stagnation or decrease in performance that will not resume for several weeks or months (16). Overtraining Syndrome (OTS) is the most extreme outcome produced by excessive training overload and/or non-training stresses. Two additional words are described to supplement the purpose of recognizing the early signs and symptoms of OTS in athletes respective to training programs and performance. Raglin and Morgan introduced the following terms in their extensive research on collegiate swimmers: Staleness is a state where an athlete is unable to train at customary levels and suffers a persistent decrement in performance. Distress is defined as an athlete experiencing one or more signs or symptoms of OT, which serves as an indicator for staleness if recovery remains inadequate (18,21). Causes for Overtraining Syndrome There are many proposed hypotheses in the scientific literature on the causes of OTS. Kirwan and colleagues studied the effect of inadequate carbohydrate replacement following repeated days of intense exercise and observed decreased VO2max, decreased running economy, and increased ratings of perceived effort (12). This theory, deemed the glycogen hypothesis, suggests general fatigue and the feeling of "heavy legs" are due to reduced muscle glycogen (12,22). Several hypotheses suggest disruptions in the hypothalamic pituitary axis cause a cascade of hormonal responses associated with OTS (2,9,10,13,24). Additionally, the glutamine hypothesis describes immune-related responses linked with OTS to be caused by reduced levels of plasma glutamine, an essential amino acid in immune function (25). The pathophysiology of OTS is unknown, and these are only a few of the existing hypotheses. OTS remains an elusive topic because signs and symptoms vary from one individual to the next and some "markers" of OTS have inconsistent results in various studies. Furthermore, OTS is difficult to diagnose concretely and not enough studies show how it affects performance directly. The following sections will address observable responses that may indicate OTS or the extent to which an athlete is OR. Physiological responses will also be discussed, however, these measures are more difficult to quantify without the necessary laboratory equipment or expertise in testing. If there is persistent occurrence of these signs and symptoms accompanied with an inability to train or perform at their baseline levels (distress) it is recommended that training load be reduced and/or recovery be enhanced to prevent staleness or the more serious OTS. Observable Responses The most basic of observable symptoms of OR is a decline in performance despite an increase in training load. This will usually capture the eye of a coach, however, it needn't be the first sign. Ideally, if these performance drops can be avoided, an athlete can experience less breaks in momentum and leave less to question about what is achievable on a consistent basis. In general, one of the first observable signs of OR is a change in mood (18,21,22). Although exercise promotes positive mental health on the whole, some types of training are known to have detrimental psychological effects (21). Periods of OT have been associated with worsened mood; furthermore there is a relationship between increasing training load and worsening mood, and when training was reduced, mood improved (18,21). Another observable sign is constant fatigue. The mechanism behind chronic fatigue in athletes is very similar to the mechanism behind mood disturbance. Lucille Smith suggests in her work that repeated tissue trauma results in elevated blood levels of pro-inflammatory cytokines that communicate with cells in the brain and induce a behavior change that is more appropriate for a sick or injured person in the body's attempt to recover (22). This can explain an array of mood and behavioral changes seen in OTS such as: depression, changes in sleep patterns, reduced appetite, difficulty concentrating, easily distracted, and decreased self-esteem (22). Cytokines may also affect another area of the brain, the hippocampus, which could disrupt memory and learning. Besides impaired academic performance, other observable information processing skills can be affected including loss of coordination, difficulty concentrating, decreased ability to deal with large amounts of information, and reduced capacity to correct technical faults (22). One final observable sign of OTS that should be mentioned is injury. Intense exercise can lead to muscle fiber damage with indicators such as soreness, edema, and protein release into plasma (5). If damage continues a muscle injury may result from continued breakdown of tissue and inadequate means for repair. Excessive tissue damage can lead to overuse injuries, pain, loss of function, and changes in biomechanics affecting economy and VO2max. If that isn't enough, since the immune system has to redirect its' efforts to heal the injury, the injured athlete is more susceptible to illness, infections, allergies, headaches, and gastrointestinal disturbances (22). Phsiological Responses Heart Rate Variability (HRV) has been extensively researched in the area of OTS. The theory behind this response is that intensified training results in altered autonomic cardiovascular activity towards parasympathetic inhibition and sympathetic activation (3). It has been proposed that HRV monitoring is a suitable means to detect autonomic changes due to abrupt increases in training amount and be used as a marker to detect OTS (3). However, several studies have shown no change in HRV among overtrained athletes (4, 8), so HRV is not recommended as the sole marker for OT. Other studies have measured changes in peak oxygen uptake (VO2peak) and blood lactate concentrations. Snyder and Jeukendrup examined elite cyclists and reported a reduction in VO2peak and decreased blood lactate concentrations relative to ratings of perceived exertion in OR athletes (23). Consequently total maximal workload was also significantly decreased when the athlete was OR. As previously described, diminished muscle glycogen levels for several days can serve as an indicator of the OR or OT (12). However, muscle biopsies, which are the means of this measurement, are invasive and not realistic for real-life use. Perhaps being alert to persistent complaints of "heavy legs" is a reasonable enough substitute to assume the athlete may be experiencing the symptoms of reduced muscle glycogen. Other studies have questioned whether excessive exercise-induced inflammation can cause symptoms of OTS. The body's response to tissue damage is up-regulation of acute inflammation, and the production of new acute-phase proteins due to altered liver functioning (22). Examples of acute-phase proteins include plasma DNA, creatine kinase (CK), and C-reactive protein (CRP). Fatouros et al. studied athletes for 3 weeks while increasing intensity and found measured plasma DNA levels to markedly increase, CRP levels to increase 400 percent, and CK levels increase as well (5). Hormonal responses characterize yet another area in OTS. Hormones play a role in redistributing metabolic fuels, maintaining blood glucose, and enhancing the responsiveness of the cardiovascular system. Repeated exposure to stress may lead to altered responsiveness to sub-increased or decreased neurotransmitter response and receptor function (1). Uusitalo studied the hormonal responses in female endurance athletes and found decreased sympathoadrenal and/or adrenocortical activity (or exhaustion of the adrenal gland) with heavy training- induced stress (24). Meeusen et al. (2008) found increased concentrations of cortisol, ACTH, and prolactin in athletes with OTS. Furthermore, this study used a two-bout exercise protocol and found ACTH and prolactin reactions in the second exercise bout were much higher in athletes considered to be NFOR compared with OTS (15). This is an intriguing finding because this protocol could be a useful tool in diagnosing NFOR and OTS. Additionally, researchers are also exploring the lesser-referenced hormone levels, such as leptin, adiponectin, and ghrelin in endurance athletes (10,16). Although hormonal responses appear to be strong in OTS, there are numerous problems with collecting hormonal data and controlling for various factors that may interfere with results (6,16). Recommendations for Recognizing and Preventing OTS It is apparent that diagnosing OTS is a task even researchers are struggling with. There is an abundant search to find the magi cal "marker" for OTS, but testing has its limitations and may not reflect OTS in all cases (6). Why then, would we expect athletes or coaches to diagnose OTS or distinguish OR from OT? As athletes and coaches we should shift our attention away from trying to label the condition and focus on managing signs and symptoms of training stress with recovery to avoid NFOR and OTS. This can be aided by monitoring performance, keeping meticulous records of training and competition, increasing training load gradually, and being mindful of psychological stress which may be additive to the physical stress of training (22). Furthermore, understanding physiological responses in OTS is excellent knowledge to have if you are invested in the sport, but it is unrealistic, time costly, and expensive to test for these responses in every-day life. Practical Solutions for Recognizing and Preventing OTS If there is still a yearning for more concrete information on the training status of an individual, there are a few inexpensive and non-invasive ways for that to be quantified. The Profile of Mood States (POMS), developed by Raglin and Morgan in an attempt to identify athletes at risk of training-induced distress, has become a popular reference and resource for OTS and the field of sports psychology (11). In their assessment, POMS resulted in a mean prediction rate for identifying distressed swimmers of 93.9 percent men and 100 percent for women; results were also similar among collegiate track and field athletes (21). Seven items within POMS were identified as predictor variables and had an average accuracy of 69.1 percent (37 percent above the chance rate of prediction). The findings from this paper supports suggestions that psychometric monitoring is a valuable means of preventing staleness (18,21). In conjunction with mood disturbances measured by POMS, increased salivary cortisol levels have been shown to be significantly correlated with depressed mood during overtraining, but not at baseline or taper (20). Salivary cortisol tests offer a non-invasive measure of hormonal responses and could be an excellent accompanying test to POMS. As previously mentioned, there are several symptoms of OTS associated with cognitive impairment. The affected central mechanisms are the basis for another exciting development in diagnosing OTS by testing psychomotor speed. Nederhof et al. tested athletes before and after training camp and two weeks after on reaction time. Athletes experiencing FOR had longer reaction times after camp compared to baseline levels and to the control group (19). Psychomotor speed in these studies is tested using a computer program that offers an objective and affordable measurement. Testing a similar concept, Lehman et al. examined neuromuscular excitability (NME) and found it to rapidly deteriorate in overtraining athletes (14). Psychomotor speed testing and NME could offer quick, inexpensive and practical markers for detecting early signs of OTS.
The purpose of this paper is to give athletes and coaches a better understanding of the components of successful training, how OT accumulates and escalates without proper recovery, and the observable and physiological signs and symptoms of OTS. Having a better sense for all of these consequences can prevent OTS and performance pitfalls. Further research is needed with OTS; information on how it affects performance is lacking and most researchers seem stuck on trying to find the one marker to diagnose OTS. As shown in this paper, there are almost infinite responses as a consequence of OTS and not all individuals experience the same symptoms. Meur et al. is one of the few studies to take a multidisciplinary approach to detecting OTS, understanding, that there are several variables involved in the process (17). It would be of interest to see more research like this done in future studies. Nevertheless, there are promising methods being developed to test for the training status of an individual. If these tests are unavailable to the athlete and coach, however, much can be gained from simply recognizing signs and symptoms of OTS. References 1. Armstrong, L. E. and VanHeest J.L. "The Unknown Mechanism of the Overtraining Syndrome Clues from Depression and Psychoneuroimmunology," Sports Med, 32 (3) 185-209, 2002. 2. Barron, J.L., Noakes, T.D., Levy, W, Smith, C, Millar, R.P. "Hypothalamic dysfunction in overtrained athletes," J Clin Endocrinol Metab., 60 (4):803-6, 1985. 3. Baumert, M, Brechtel, L., Lock, J., Hermsdolf, R.W., Baier, V., and Voss, A. "Heart Rate Variability, Blood Pressure Variability, and Baroreflex sensitivity in Overtrained Athletes," Clinical J Sport Med., 16:412-417,2006. 4. Bosquet, L., Papelier, Y, Leger, L., Legros, P. "Night heart rate variability in male endurance athletes," J Sports Med Phys Fitness, 43:506-12,2003. 5. Fatouros, LG., Destouni, A, Margonis, K,Jamurtas, A.Z.,Vrettou, C, Kouretas,D., Mastorakos, G. Mitrakou, A., Taxildaris, K, Kanavakis, E., and Papassotiriou, L "Cell-Free Plasma DNA as a Novel Marker of Aseptic Inflammation Severity Related to Exercise Overtraining" Clinical Chemistry, 52,(9) 1820-24,2006. 6. Gastmann, U., Petersen, KG., Bocker J., Lehmann, M 'Monitoring intensive endurance training at moderate energetic demands using resting laboratory markers failed to recognize an early overtraining stage," J Sports Med Phys Fitness, 38(3):188- 93,1998. 7. Halson, S.L. and Jeukendrup, AE. "Does Overtraining Exist? An Analysis of Overreaching and Overtraining Research," Sports Med, 34 (14): 967-981,2004. 8. Hedelin, R., Kenatta, G. Wiklund, U., Bjerle, P., HenrilcssonLarsen, K "Short-term overtraining: effects on performance, circulatory responses, and heart rate variability," Medicine & Science in Sports & Exercise, 32(8)3480-1484, 2000. 9. 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Lehmann, M, Baumgartl, P., Wiesenack, C, Seidel, A., Baumann, H., Fischer, S., Spori, U., Gendrisch, G., Kaminski, R. and Keul, J. "Training-overtraining: influence of a defined increase in training volume vs training intensity on performance, catecholamines and some metabolic parameters in experienced middle- and long-distance runners," European Journal of Applied Physiology, 64:169-177, 1992. 14. Lehmann, M, Baur, S., Netzer, N, and Gastmann, U. 'Monitoring high-intensity endurance training using neuromuscular excitability to recognize overtraining," European Journal of Applied Physiology, 76:187±191, 1997. 15. Meeusen, R., Nederhof, E., Buyse, L., Roelands, B., Schutter, G., Piacentini, M.E, "Diagnosing overtraining in athletes using the two-bout exercise protocol," British J Sports Med., 44:642-648,2008. 16. 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 and the American College of Sports Medicine," Medicine and Science in Sports and Exercise, 186-205,2012. 17. Meur, Y.L., Hausswirth, C, Natta, E, Couturier, A. Bignet, F. and Vidal, P.P. "A multidisciplinary approach to overreaching detection in endurance trained athletes," J Appl Physiol., 114:411-420, 2013. 18. Morgan, WP., Brown, D.R., Raglin, J.S., O'Connor, P.J., Ellicicson, KA "Psychological Monitoring of Overtraining and Staleness," Brit. J. Sports Med., 21(3)307-114,1987. 19. Nederhof, E., Lemmink, K, Visscher, C, Meeusen, R., and Mulder, T. "Psychomotor Speed :Possibly a New Marker for Overtraining Syndrome," Sports Med., 36(10): 817-828,2006. 20. O'Connor, P.J., Morgan, WP., Raglin, J.S., Barksdale, CM., Kahn, NH. 'Mood State and Salivary Cortisol Levels Following Overtraining in Female Swimmers," Psychoneurology, 14(4):303- 310,1989. 21. Raglin, J.S., Morgan, WP. "Development of a Scale for Use in Monitoring Training-Induced Distress in Athletes." Int J. Sports Med. (15)84- 88,1994. 22. Smith, L.L. "Tissue Trauma: The Underlying Cause of Overtraining Syndrome?" Journal of Strength and Conditioning Research, 18(1), 185-193,2004. 23. Snyder, A.G., Jeukendrup, A.E., Hesselink, MK, Kuipers, H., Foster C. "A physiologicallpsychological indicator of over-reaching during intensive training," Int J Sports Med., 14(1):29-32,1993. 24. Uusitalo, ALT., Huttunen, P., Hanin, Y, Uusitalo, A.P., Rusko, H.K "Hormonal responses to Endurance Training and Overtraining in Female Athletes," Clinical J of Sports Med., 8:178-186, 1998. 25. Walsh, NP., Blannin A.K, Robson P.J., Gleeson M "Glutamine, exercise and immune function. Links and possible mechanisms," Sports Med., 26(3):177-91, 1998. Bio Ann Detmer is the Graduate Assistant at the University of Kentucky pursuing a degree in Exercise Physiology. Prior to her arrival in Kentucky, she served as assistant coach for three years at the University of California-Berkeley. She was a part of the track and field and cross country teams at the University of Wisconsin-Madison, where she graduated in 2008.
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Staying on Track – Recognition of Overtraining Syndrome in Endurance Athletics
Final Remarks
