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In sports, an increased training load can cause a source of pressure on the individual athlete. Frequently, inadequate loading and high training magnitudes are associated with the body’s inability to adapt to the desired load. That can affect performance and increase the risk of injury among athletes.

High-intensity training causes stress build-up, which eventually alters the physical and psychological aspects of the athlete. For example, prolonged training with increased load is associated with an increased risk factor for illnesses. This relationship between the athlete’s health status and increased loading is represented in the medical literature as a continuum paradigm. This paradigm shifts between acute fatigue symptoms, overreaching conditions, and lastly, overtraining syndrome (OTS).


OTS is defined as conditions of prolonged fatigue and decreased performance present for more than two weeks. Also, in OTS, the persistent exposure to high-stress levels can weaken the immune system, making the athlete more vulnerable to acute illnesses.

Overreaching is essentially an earlier stage before OTS develops. In this condition, prolonged exposure to training load would result in underperformance and fatigue. If such a state continues, it can develop into OTS. An adequate recovery can shift and reverse the process of overtraining development. However, the amount of time of recovery required to return to prior performance would ultimately determine the diagnosis of overreaching versus OTS. For instance, a decreased performance that is longer than two months is associated with OTS.

What are the symptoms of overtraining?

OTS is characterized as prolonged, unexplained underperformance and increased incidence of illness, along with other physical symptoms, such as chronic fatigue and high-stress levels. Symptoms of OTS can also be detected by examining an athlete’s behavioral characteristics and emotional state. Hence, loss of motivation, mood disturbances, anxiety, insomnia, restlessness, weight loss, inability to maintain concentration, depression, and other inadequate physical signs are potential symptoms of OTS.

What are the causes of overtraining?

The shift from a homeostatic condition to an OTS state is described on a continuum spectrum. Two crucial factors that can affect this spectrum of conditions are load and recovery. When the two elements are not synergistically coupled, it increases the stress on the body’s systems. Eventually, if balance is not reached, more severe conditions may develop, such as overreaching and OTS.

Hence, the cause of OTS is linked to the build-up of physiological and psychological stress factors. In addition, maladaptive nutrition programs and low-quality sleep routines can increase physiological stress on the body. Finally, inadequate responses to uncontrolled emotional states from excessive training have the potential risk to elevate psychological stress factors.

What are the possible hazards of overtraining?

The inability to cope with a high training load can have a negative influence on athletes’ health. Potential hazards of OTS are linked to the physical and psychological aspects of athletes’ well-being. Neglected or untreated signs of physical symptoms can progress from acute fatigue conditions, overreaching, and OTS, and can eventually lead to severe clinical injuries and illnesses.

For example, this progression, if overlooked, may lead to chronic immune dysfunction and immune suppression that makes athletes more prone to infectious diseases. Thus, early and appropriate diagnosis of OTS symptoms reduces the potential health risks. Another possible hazard is related to impaired psychological behavior that leads to underperformance of athletes with OTS. This reduced ability to maintain normal performance negatively affects athletes’ mood, sleep quality, and appetite.

Relationship between overtraining and oxidative stress:

High-intensity physical exercise generates reactive oxygen species (ROS), resulting in elevated oxidative stress at the molecular level affecting multiple organs. In this state, inflammatory responses are elevated, and it alters the body’s immunity status. Dysfunction of the body’s immune system increases vulnerability to infectious agents and, consequently, enhances the risk of illness.

In OTS, ROS production occurs at a proportional ratio to the load or stress applied to the body. Furthermore, inflammation responses during OTS occur at a higher rate. For example, white blood cells like neutrophils and macrophages generate free radicals that can increase oxidative stress accumulation.

Interestingly, oxidative stress biomarkers at rest are also shown to be higher in OTS athletes. This long exposure to ROS accumulation in OTS not only alters and promotes immune dysfunction but also weakens the antioxidant defense system. As a result, oxidative stress can become pathological, making the OTS athletes more prone to oxidative damage.

Physiological biomarkers used to detect OTS:

Oxidative stress and immunologic biomarkers can be used to investigate the occurrence of OTS. Various studies have examined the ratio of oxidized glutathione and urinary levels of isoprostanes to detect the relationship between training load and oxidative stress. Therefore, oxidative stress biomarkers, along with other biochemical measurements, can provide the necessary information regarding the accumulation of ROS and the activity of the antioxidant defense system during OTS. Moreover, to detect immunity alterations and the existence of inflammation response, a leukocyte count can be used.

Treatment/ Prevention:

It is suggested that during recovery, the athlete would stop all participation in his/her sport. However, to maintain an adequate fitness level, during the resting period, it is recommended that the athlete participates in low-level aerobic activities. Returning to a sport would be allowed when all symptoms are completely resolved. An appropriate training regime with adequate breaks and recovery period would reduce the risk of developing OTS.