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Overtraining—what happens when you do too much

Overtraining syndrome (OTS) is what can occur if you push your training regime too far. Signs of OTS are chronic fatigue and declining performance despite continued training. Recuperation can take weeks or even months.

From the Field

Is it possible to do too much training? What are the dangers of going too far?




In order to reach your peak of performance, both physically and mentally, you have to push your training beyond what’s comfortable to realize continued performance gains.. However, it is possible to do too much if you don’t take appropriate rest periods and if you don’t get optimum nutrition. The result is chronic fatigue, declining performance, and other symptoms of what is known as “overtraining syndrome” or OTS. Recovering from this condition can take a warrior out of active duty for weeks or even months while recuperating.


For Warfighters to develop the total fitness and resilience needed to face the demands placed on them, they have to train much the same as if they were elite athletes. Thus we can learn important lessons from those athletes and the studies surrounding professional athletes. One of those lessons is that it is possible to do too much, leading to extreme, persistent physical and mental fatigue. The results are known as “functional overreaching” (FO), “nonfunctional overreaching” (NFO), and, at the worst, “overtraining syndrome” (OTS). The only significant difference between the three is the severity of the symptoms and how long it takes to recuperate before training—and in the case of Warfighters, active duty—can resume.

Myths and/or Claims

The myth that generates OTS is that “more is better.” In fact, more is not always better; in training, more can reach the point of “too much.” And more training needs to be accompanied by more strategic rest periods and more optimum nutrition.


Overtraining occurs when aggressive physical training is not accompanied by appropriate periods of rest and optimum nutrition. It ranges from FO, which usually requires days to recover, through NFO, which takes weeks for recovery, to OTS, which needs months or even years of recuperation. The best course is to avoid overtraining altogether, but the difficulty is that it is hard to draw the line between enough training and too much when pushing to limit to achieve peak performance. In addition, the symptoms of overtraining are diverse, and it is only when they become chronic that NFO or OTS has set in—by which time it is too late.

The most pervasive symptoms are a decline in physical performance despite continued training accompanied by pronounced, persistent fatigue. Other symptoms include insomnia, change in appetite, irritability, restlessness, excitability, anxiousness, loss of weight, loss of motivation, inability to concentrate, depression, apathy, and changes in resting heart rate and blood pressure. In fact, some of the best warning signs that an athlete or warrior is approaching overtraining come from some of these more subjective symptoms. One useful tool is a training distress questionnaire that focuses on these mood-related symptoms.


The extreme environments and/or high-intensity operational demands to which Warfighters are routinely subjected can increase susceptibility to OTS, so military personnel need to take extra precautions to ensure that physical activities are punctuated with adequate rest periods and good nutrition. Chapter 5 of the Warfighter Nutrition Guide provides information for Warfighters both in training and deployed.

Summary for Military Relevance

Because NFO and OTS lead to significant down time for Warfighters and other military personnel, prevention is crucial. This means design of training programs that incorporate both appropriate rest periods and diet. HPRC provides information on Warfighter-specific nutritional needs on its Nutrition Resources web page. Training adaptations that target OT prevention include adjustments to running mileage, use of interval training, and graduated training periods, along with close monitoring of both physical and mental conditions of trainees. Detailed information and references to specific studies are provided in the HPRC’s Research Summary “Overtraining: How to Avoid It; How to Detect It.”

*Bottom Line Up Front

Research Summary


Key Points

  • Reaching peak performance levels usually requires that you train beyond your body’s normal comfort range.
  • Too much training without adequate recovery periods can lead to overtraining, which can require months of recuperation.
  • The most consistent symptoms of overtraining are chronic fatigue and decline in performance despite continued training.
  • Overtraining syndrome includes both physical and mental components.
  • Overtraining is difficult to diagnose and difficult to predict, so it is important to practice preventive measures during training.


    In order to achieve peak performance, it is necessary to overload—that is, push your training beyond the point of normal comfort, stressing your mind and body to continually improve your condition. However, when pushed too far and/or too long, overload can result in extreme, persistent physical and mental fatigue. This condition is known as “overtraining syndrome” (OTS), sometimes also referred to as “staleness.” The condition is well studied in the athletic community, and as is true of so much research on elite athletes, overtraining (OT) studies may apply equally well to Warfighters who are engaged in heavy and high volume training programs often coupled with high intensity operational demands.

    The symptoms of OT have been described as chronic fatigue, burnout, and staleness. The result is an overwhelming physiological and psychological burnout and a serious performance decrement that can take weeks or months—even years—to overcome. Some form of overtraining has been found to occur in anywhere from seven to 60% of athletes at some point in their careers.1,2


    Perhaps the most pervasive and dangerous myth in physical fitness training is that “more is better.” To reach the level of optimum conditioning so valuable to a Warfighter, it is necessary overload during training, but it must be accomplished without doing damage to one’s system. As a result, it is important to determine where the boundary lies between “more” and “too much.”

    Facts and Evidence

    Short-term overtraining—more correctly referred to as functional overreaching (FO), or just overreaching—is considered by many athletes and professional trainers to be an essential component in achieving optimum athletic performance. It addresses both the physical and mental aspects of conditioning and requires a careful balance of training with adequate rest and recovery. When this balance is upset by inadequate recovery periods, a range of overtraining conditions result depending on how long the imbalance continues. This range extends from FO, which usually takes just days to recover, through “nonfunctional overreaching” (NFO), with recovery periods of weeks to months, to “overtraining syndrome” (OTS), which requires months or even years to recover from.2

    OTS and NFO can be diagnosed by a set of symptoms typified by a decline in physical performance despite continued training, often accompanied by pronounced fatigue. These are often associated with one or more of the following: insomnia, change in appetite, irritability, restlessness, excitability, anxiousness, loss of weight, loss of motivation, inability to concentrate, depression, apathy, and changes in resting heart rate and blood pressure.3 Nevertheless, diagnosis can be difficult because the underlying biochemical mechanism is not understood. Identification largely depends on eliminating other possible sources of the key symptoms, including anemia, magnesium deficiency, viral infections, muscle damage with abnormal creatine kinase levels, Lyme disease, diabetes, thyroid disorders, adrenal dysfunction, eating disorders, depression, allergies, cardiovascular disease, and asthma. It is crucial that a diagnostician question a patient for subjective input as well as background of training practices in order to distinguish OTS from purely physiological fatigue. Key subjective sensations include tiredness, languor, lassitude, lethargy, and poor concentration. OTS fatigue involves both physical and mental aspects, and it is distinct from that of chronic fatigue syndrome and Epstein-Barr in that the athlete continues to train despite his or her decline in performance. One useful tool is a training distress questionnaire, which includes subject measures of mood dimensions.4 Monitoring of emotional state, including mood, stress, and anxiety, also has potential value.5

    Currently, there is no single reliable diagnostic signal that a person is on the verge of overtraining to the point of NFO or OTS. Moreover, diet and use of dietary supplements can affect the rate at which overtraining progresses and symptoms occur. And potentially useful generalizations have been hampered by the lack of rigorous definitions for overtraining and overreaching, which make it difficult to compare original research papers that cover different levels of the condition; most, in fact, seem to address conditions of overreaching rather than overtraining.6 Ideally, the athlete should be able to watch for measures of dangerous overtraining/overreaching, but to date there is no easy-to-use set of warning markers. A summary of biomarkers useful for medical professionals was recently assembled.4


    Overtraining appears to be a necessary part of achieving peak performance, so the possibility of OTS is a serious consideration in sports and military environments, particularly when coupled with extreme environments and/or high intensity operational demands. Athletes and Warfighters need to ensure that they schedule adequate rest and recovery periods in the course of overtraining procedures.

    The impact of diet, dietary supplements, and medications must be taken into consideration in evaluating whether symptoms related to OTS have been affected or even induced by these other factors. Many of the studies of OTS did not include control for these variables.4 Nutrient-based biomarkers include serotonin, tryptophan, glutamine, and glycogen, but none is entirely satisfactory, and research continues on the effects of nutrients on OTS. One easy-to-follow suggestion, however, is to ensure that adequate sources of carbohydrates are consumed to maintain energy during training. The most recent sources emphasize a combination of carbohydrates and protein in certain ratios.3,4,7-9Chapter 5 of the Warfighter Nutrition Guide provides detailed information on training-related nutrition for Warfighters.

    It is also essential that the clinician explore other possible sources of similar symptoms before making a diagnosis of OTS or even NFO.3 As mentioned above, there is a host of other possible diagnoses.

    Military Relevance

    Given the lack of early diagnostic markers for OTS and its potential long-term impact on performance, the military needs to focus on prevention. The alternative is performance decline in Warfighters who could require months to recover to optimum or even acceptable condition. Even NFO typically requires two weeks to recover.4 Few military personnel can be provided with the long-term down time required to recover from OTS, and the cost impact on the military could be considerable if the potential result of continuous overtraining is ignored.

    Prevention involves design of training programs that build in alternating periods of intense training and rest.1,9 This must be accompanied by a diet that supports this type of training, including sufficient carbohydrates, protein, and other essential nutrients, as well a proper timing of nutrient intake relative to exercise.3,8-11 Such a diet is significantly different from that of the average “weekend warrior.” Resources for Warfighter-specific nutrition such as the Warfighter Nutrition Guide are available through HPRC’s Nutrition Resources web page.

    Prevention also involves monitoring of both physical performance and mental condition1,3,12, and a recent review focusing on military training presented specific recommendations for the prevention of overtraining.8 Key recommendations include education of leaders and trainees integrated into an injury prevention program and greater command responsibility for training-related injuries to encourage monitoring of trainees and training protocols.8 Specific training points relevant to prevention of OTS include:

    • reduction of running mileage (but not marching mileage);
    • more gradual increases in running mileage to allow greater adaptation time;
    • testing new recruits for initial condition and placing them in training groups according to ability;
    • giving less-fit recruits a longer initial training period rather than more training sessions within a shorter period;
    • incorporating interval training into running programs; and
    • ensuring that carbohydrate- and protein-restoring nutrients are consumed within 60 minutes of glycogen-depleting, muscle-fatiguing activity whenever possible;

    An experimental modified Air Force PT program incorporated some of these and other considerations aimed at reducing the trainee attrition rate, including incidence of overtraining.13 Among other strongly positive results, completion of training increased 83%, overuse injuries decreased 67%, and overtraining was virtually eliminated.

    An additional consideration in prevention of OTS is that mental toughness and resilience could enable Warfighters to cope better with the increased demands of intense military training. Since OTS includes mental and emotional factors, conditioning similar to the resilience training practiced by elite athletes may be another key to prevention. Preliminary studies on the impact of mental toughness in preventing burnout are promising.4,14


    “More is better” works only when it refers to more recovery time in proportion to more training, coupled with optimum nutrition. Once overtraining syndrome (OTS), or even non-functional overreaching (NFO), has set in, the only recourse is rest, good nutrition, and reduction in stress. The result is a Warfighter who cannot serve for weeks or even months. The best solution to OTS and NFO is prevention. Training should involve adaptive methods of physical exercise, good nutrition, development of mental toughness and resilience, and good equipment.



    1. Alves RN, Costa LOP, Samulski DM. Monitoring and prevention of overtraining in athletes. Rev Bras Med Esporte. 2006;12(5):262e-6e.
    2. Nederhof E. Psychomotor speed as a marker for overtaining in athletes: A multidisciplinary approach [Doctoral]. Delft, Netherlands: University Medical Center Groningen, University of Groningen; 2007.
    3. Meeusen R, Duclos M, Gleeson M, Rietjens G, et al. Prevention, diagnosis and treatment of the overtraining syndrome:  ECSS position statement 'Task Force'. Eur J Sport Sci. 2006;6(1):1-14.
    4. Purvis D, Gonsalves S, Deuster PA. Physiological and Psychological Fatigue in Extreme Conditions: Overtraining and Elite Athletes. PM&R. 2010;2:442-50.
    5. Roose J, Vries Wd, Schmikli S, Backx F, et al. Mood scores as predictor of run performance profiles in adolescent athletes. Medicina Sportiva. 2009;13(3):163-70.
    6. Halson SL, Jeukendrup AE. Does overtraining exist? An analysis of overreaching and overtraining research. Sports Med. 2004;34(14):967-81.
    7. Campbell JA. Quantitative and qualitative recovery in trained females after an exhaustive resistance training protocol, and with a post-exercise carbohydrate-protein beverage. Tuscaloosa, Alabama: Kinesiology, University of Alabama; 2010.
    8. Bullock SH, Jones BH, Gilchrist J, Marshall SW. Prevention of Physical Training-Related Injuries: Recommendations for the Military and Other Active Populations Based on Expedited Systematic Review. American Journal of Preventive Medicine. 2010;38(1S):S156-S81.
    9. Lowery L, Forsythe CE. Protein and Overtraining: Potential Applications for Free-Living Athletes. Journal of the International Society of Sports Nutrition. 2006;3(1):42-50.
    10. Petibois C, Cazorla G, Poortmans JR, Deleris G. Biochemical aspects of overtraining in endurance sports: a review. Sports Med. 2002;32(13):867-78.
    11. Urhausen A, Kindermann W. Diagnosis of overtraining: what tools do we have? Sports Med. 2002;32(2):95-102.
    12. Kellmann M. Preventing overtraining in athletes in high-intensity sports and stress/recovery monitoring. Scandinavian Journal of Medicine & Science in Sports. 2010;20(2):95-102.Walker TB, Lennemann L, Zupan MF, Anderson V, et al. Adaptations to a New Physical Training Program in the Combat Controller Training Pipeline. Brooks City-Base, Texas: Air Force Research Laboratory;2010.
    13. Nicholls AR, Polman RCJ, Levy AR, Backhouse SH. Mental toughness, optimism, pessimism, and coping among athletes. Personality and Individual Differences. 2008;44(2008):1182-92.