, Volume 33, Issue 10, pp 771-781
Date: 23 Sep 2012

Elucidating the Unexplained Underperformance Syndrome in Endurance Athletes

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Abstract

The unexplained underperformance syndrome (UPS), previously known as the overtraining syndrome (OTS), has been defined as a persistent decrement in athletic performance capacity despite 2 weeks of relative rest. It has been proposed that UPS may be caused by excessive cytokine release during and following exercise causing a chronic inflammatory state and ‘cytokine sickness’. This article extends that hypothesis by proposing that time-dependent sensitisation could provide a model through which the aetiology of UPS may be explained. In this model, the principal abnormal factors in UPS are an increased production of and/or intolerance to interleukin (IL)-6 during exercise. Strategies to attenuate the IL-6 response to exercise that may also reduce an athlete’s susceptibility to UPS are proposed.