Unexplained underperformance in athletes is a common problem, occurring in around 10–20% of elite endurance squads.¹ The terms “overtraining syndrome”, “staleness”, “chronic fatigue in athletes”, and “sports fatigue syndrome” have been used.² “Burn out” with depressed mood state may occur in power athletes. There has been some confusion in the literature on the definition and diagnostic criteria. On 19 April 1999 the authors held a round table discussion at St Catherine's College, Oxford in order to clarify the diagnostic criteria to be used in the future. The format of the meeting was modelled on the consensus meeting held at Green College, Oxford on 23 March 1990 on the criteria for diagnosis of patients with chronic fatigue.³

Unfortunately the term overtraining syndrome implies causation, which limits investigations of this …