When training makes you ill: the downside of ambitious sport
Regular training is one of the most effective measures for physical and mental health. However, anyone who consistently trains more than the body can recover from risks the opposite: a state of chronic exhaustion summarised under the term overtraining syndrome. Those affected are by no means only professional athletes – chronic overload also occurs repeatedly among recreational athletes, such as marathon runners, triathletes or in intensive strength training.
This article explains how overtraining can be recognised early, how overreaching in sport differs from overtraining syndrome, and why a medical assessment can be useful.
Overreaching versus overtraining syndrome: what is the difference?
A temporary dip in performance after intensive training phases is normal and even intended – experts refer to this as functional overreaching. After a few days to two weeks of recovery, an increase in performance usually follows (supercompensation).
Three stages of overload
- Functional overreaching: Short-term exhaustion that subsides within a few days with planned recovery. It is part of a well-designed training plan.
- Non-functional overreaching: Performance remains reduced over weeks. Initial hormonal and psychological changes occur.
- Overtraining syndrome (OTS): A sustained state of exhaustion that can often last for months. Other causes (e.g. infections, deficiency states, thyroid disorders) must be ruled out medically.
The transitions are fluid, which is why careful observation of one's own training and well-being is important.
Symptoms of overtraining: physical warning signs
The symptoms of overtraining are varied and affect virtually all organ systems. They are characteristically slow to develop and are easily overlooked at first.
Typical physical signs
- Performance drop despite training: Familiar loads feel harder, personal bests move out of reach.
- Prolonged recovery times: Muscle soreness lasts longer, the pulse takes considerably longer to normalise after exertion.
- Altered resting heart rate: Both a persistently elevated morning pulse and an unusually low value can be indications.
- Sleep disturbances: Difficulty falling asleep, restless sleep or the feeling of not being rested in the morning.
- Frequent infections: Colds, sore throats or flu-like illnesses become more common – the immune system is weakened.
- Muscle and joint complaints: Diffuse pain, frequent minor injuries or a susceptibility to tendon irritation.
- Changes in appetite and weight: Loss of appetite or unintentional weight loss can occur.
- Hormonal abnormalities: Women may experience menstrual cycle disturbances; men may experience a loss of libido.
Mental and emotional warning signs
In addition to physical complaints, clear psychological changes often appear in overtraining syndrome. They are often the first indications – but are rarely associated with sport.
Psychological signs
- Persistent fatigue and lack of drive
- Irritability, mood swings or depressive moods
- Loss of enjoyment in training and declining motivation
- Concentration problems in everyday life or at work
- Inner restlessness, sometimes accompanied by anxiety
- Feelings of emotional emptiness or "burnout"
These symptoms resemble a depressive episode and can in fact overlap with one. It is all the more important to have the connection to sporting load assessed professionally.
How does overtraining syndrome develop?
Overtraining usually does not result from a single hard training session, but from a mismatch between load and recovery over a longer period. Contributing factors include:
- Excessive training volumes or intensities without sufficient recovery
- Monotonous training design
- Inadequate energy intake (relative energy deficiency in sport, RED-S)
- Lack of sleep
- Occupational or private stress adding to physical strain
- Frequent competitions without recovery phases
- Previous infections that have not been fully cured
The combination of several factors – such as intensive training during phases of high occupational strain – is particularly risky.
Why medical assessment is important
Many symptoms of overtraining syndrome are non-specific and can have other causes. These include iron deficiency, vitamin D deficiency, thyroid dysfunction, cardiovascular conditions, chronic infections or depressive disorders. A medical examination can help to clarify these differential diagnoses.
Possible components of an assessment
- Detailed discussion of training, nutrition, sleep and stress
- Physical examination
- Laboratory tests (e.g. blood count, iron status, thyroid values, inflammatory parameters, hormone status)
- Exercise ECG or performance diagnostics if required
- Recording of heart rate variability as a supplementary indicator of recovery status
Early assessment can prevent a manageable phase of non-functional overreaching from developing into a prolonged overtraining syndrome that impairs athletic performance or quality of life for months.
What those affected can do themselves
Anyone who notices signs of overtraining should not continue their training programme unchanged. Proven measures are:
- Reducing or pausing training, coordinated with medical or sports medicine advice
- Improving sleep hygiene: regular times, sufficient darkness, no late evening training before bed
- Reviewing energy and nutrient intake: sufficient calories, enough carbohydrates, protein and micronutrients
- Stress management: deliberate recovery phases, relaxation techniques
- Keeping a training log: documenting load, well-being, resting heart rate and sleep
- Involving the social environment: family, coaches or training partners often notice changes earlier
Prevention is better than cure
A well-thought-out training plan with targeted recovery phases, regular reassessments and realistic goals is the best prevention. Anyone who plans load and recovery in a balanced way benefits in the long term – both in performance development and in health.
In the case of persistent complaints, an unclear drop in performance or symptoms lasting longer than two weeks, a sports or general medical assessment is advisable. It can contribute to clarification and helps in planning individually appropriate measures.
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This article does not replace medical advice.