The overtraining syndrome is caused by excess frequency, volume or intensity of physical training, in addition to lack of rest and recovery after exercise. It causes fatigue and a sharp decline in performance. It usually occurs in professional athletes due to poor training planning, sometimes it lasts up to 6 months and can ruin a sports career.
One of the clearest symptoms is a sharp rise in the concentration of epinephrine and norepinephrine beyond normal levels induced by exercise. In addition, scientists have recently proposed that overtraining could be caused by an overproduction of the neurotransmitter serotonin , the "hormone of good humor", which when produced in excess is associated with sleep and tiredness.
