Causes and Cures of Overtraining Syndrome

By Rick Morris

The United States Olympic Committee and the American College of Sports Medicine define overtraining as an “untreated overreaching that results in chronic decreases in performance and impaired ability to train.” The Oxford Dictionary of Sports Science and Medicine defines it as “a combination of signs and symptoms of over training which typically causes the sufferer to feel mentally fatigued in absence of physical fatigue and causes deterioration of performance. Overreaching is understood to be the initial and mild precursor to over training syndrome. A slight decrease in performance due to overreaching, if left untreated, may become the more dramatic decrease in performance of over training syndrome.

Some runners believe that over training is only a problem with very long distance running such as marathons or ultra marathons. That is just not true. Over training can strike with any physical activity involving high intensity or long duration exercise.

There are several existing theories concerning the causes of over training syndrome (OTS). In all existing theories the symptoms of OTS are the same:


  • A decrease in performance
  • Generalized fatigue
  • Depression
  • Muscle pain
  • Joint pain
  • Loss of appetite
  • Insomnia
  • Mood change
  • Fear of competition
  • Lack of motivation
  • Difficulty in concentration
  •  Increases susceptibility to illness

An athlete suffering from OTS may not have all of these symptoms, but usually will be suffering from multiple symptoms in any combination. A decreased level of performance is the primary symptom, but may be preceded by more subtle symptoms such as depression and mood changes.

Existing Theories

As was mentioned above, there are several existing theories for the cause of OTS.

One popular theory involves the hypothalamus. The hypothalamus is a deep-lying portion of the brain that is responsible for regulation almost all of the processes that affect the bodies internal environment. It plays a major role in controlling the blood levels of the hormones cortisol, epinephrine, norepinephrine and testosterone. Intense and prolonged exercise causes alterations in the levels of these hormones. This theory focuses on these alterations and their effects. Latest research seems to be showing that this alteration is a result of OTS and not a cause.

Another hypothesis involves the reduction of blood levels of the amino acid glutamine. A reduction of this important amino acid has been shown to result in impaired immune system response and an increase in the incidence of infections and illnesses.

Changes in mood and the sleep cycle have been tied to a reduction in the levels of the amino acid tryptophan. It is believed that the levels of tryptophan in the blood are caused by an increased demand for this substance by the brain. The tryptophan produces a neuro-transmitter called serotonin. Increases levels of serotonin in the brain has been shown to result in mood changes and a reduction of appetite, which are symptoms of OTC.

Another common theory is glycogen depletion. High volume or high intensity training increases the glycogen demand in order to produce the energy required. If the athlete cannot supply enough carbohydrates in their diet, a decrease level of available glycogen may result. This would account for the fatigue, decreases performance and lethargy that are common with OTC.

The last theory concentrates on the psychological stress of a training program that has no variation. Performing the same workouts day after day can adversely impact psychological performance as well as placing excessive stress on the joints and muscles.

Bringing it together

Is there a way to tie all of these theories together into a neat explainable bundle? Researchers at Appalachian State University think so. In a study published in Medicine and Science in Sports & Exercise (“Cytokine hypothesis of over training: a physiological adaptation to excessive stress?,” Medicine & Science in Sports and Exercise, Vol 32, No. 2, pp 317-331, 200) researcher Lucille Lakier Smith tried to do just that.

Smith proposes that the event that initiates OTC is a trauma to muscle, joint or skeletal systems in the body.

It is well known that intense or prolonged exercise causes micro trauma to the muscles and joints. This is the reason that all properly designed training programs include a hard day/easy day routine and also includes rest days. The easy days and rest days give the muscles and joints the recovery time needed to repair and strengthen. The micro trauma causes a mild inflammation. This inflammation is a necessary function that allows the body to make these repairs and improvements in strength. If proper rest and recovery days are included in the training program, the body completes the healing/strengthening and the inflammation withdraws.

Smith suggests that, in the presence of insufficient recovery time, the body does not completely heal/strengthen and the inflammation becomes chronic. This is the point at which a condition of “overreaching” is present. There may be mild symptoms of OTC, which a couple of days off will probably take care of. If the situation is ignored at this level, Smith suggests that the inflammation can progress to a system wide inflammation. At this point the athlete has full-blown OTC and the recovery time has increased substantially.

Smiths’ Cytokine hypothesis concentrates on the effect of hormone like messengers called cytokines. These cytokines are heavily involved in both pro-inflammatory and anti-inflammatory responses. When the mild, local inflammation of micro trauma is ignored, it becomes a chronic inflammation. At this point a large amount of pro-inflammatory cytokines are produced, which causes a system wide inflammation.

The purpose of inflammation in the body is healing. The central nervous system is activated by the cytokines involved in the inflammatory response and causes a series of “sickness” or “recuperative” behaviors, which include depression, reduced appetite, weight loss, lethargy, fear of competition and sleep disturbances. All of these are symptoms of OTC.

Cytokines binding in the hypothalamus also cause the release of cortisol. Increased levels of cortisol have been tied to mood changes and reduced lean muscle mass. Again, all symptoms of OTC.

The effects of cytokines can also explain low glycogen levels. The cytokines act on the hunger centers of the hypothalamus. They cause a decrease in hunger and appetite, which results in a decrease in calorie intake. This contributes to low levels of glycogen in the blood. Recall that low glycogen levels is a major factor in the overall feelings of fatigue involved in OTC.

In summary, Smiths’ Cytokine hypothesis suggests that over training syndrome is a healing response to the micro trauma associated with all intense and prolonged training or racing combined with insufficient rest and recovery. Coaches and trainers have known for years that intense exercise, without proper rest and recovery, may lead to OTC. Up to this point, there have been a number of separate theories to explain the cause of OTC. Smiths’ cytokine hypothesis, while a preliminary study, neatly explains a likely systematic cause of OTC and makes the treatment and avoidance of this syndrome an easier process.