Roose, de Vries, Schmikli, Backx, and van Doornen

ing-recovery balance Overtraining (OT) refers to a process based on its pre- sumed cause: OT as overtraining, meaning too much or excessive training. Numerous studies tried to find pre-dictive parameters for maladaptive signs during OT. Until now, this search did not lead to criteria for early diagnosis. Moreover, lack of consensus on definitions of OT, differ-ent study protocols, and absence of the gold standard (an undesired performance decline) led to confusion in interpreting results and conclusions, making interstudy comparisons difficult. As a tool for classification, OT research can be divided into two main approaches: single stressor (SSA), and mul-tistressor (MSA). The SSA states that too much training and/or insufficient recovery causes OT, whereas the MSA suggests that an excessive load of many stressors in life