Factors affecting performance in an ultraendurance triathlon

In the recent past, researchers have found many key physiological variables that correlate highly with endurance performance. These include maximal ox ygen uptake ((V) over dot O-2max), anaerobic threshold (AT), economy of mot ion and the fractional utilisation of oxygen uptake ((V) over dot O-2). How ever, beyond typical endurance events such as the marathon, termed 'ultraen durance' (i.e. >4 hours), performance becomes harder to predict. The ultrae ndurance triathlon (UET) is a 9-sport event consisting of a 3.8km swim and a 180km cycle, followed by a 42.2km marathon run. It has been hypothesised that these triathletes ride at approximately their ventilatory threshold (T -vent during the UET cycling phase. However, laboratory assessments of cycl ing time to exhaustion at a subject's AT peak at 255 minutes. This suggests that the AT is too great an intensity to be maintained during a UET, and t hat other factors cause detriments in prolonged performance. Potential defe ating factors include the provision of fuels and fluids due to finite gastr ic emptying rates causing changes in substrate utilisation, as well as flui d and electrolyte imbalances. Thus, an optimum ultraendurance intensity tha t may be relative to the AT intensity is needed to establish ultraendurance intensity guidelines. This optimal UET intensity could be referred to as t he ultraendurance threshold.