Relationship of exercise test variables to cycling performance in an Ironman triathlon

The purpose of this study was, firstly, to investigate the intensity of exercise performance of highly trained ultra-endurance triathletes during the cycling portion of an Ironman triathlon, and, secondly, to examine the anaerobic threshold and its relationship to this performance. Following a peak oxygen consumption ((V) over dot (O2peak))) test on a cycle ergometer to determine the heart rate (HRTh,vent) and power Output (POTh,vent) at the ventilatory threshold (Th-vent), 11 highly trained male triathletes [mean (SEM) age 35.8 (1.6) years, body fat 11.7 (1.2)%. ((V) over dot (O2peak))) 67.5 (1.0) ml(.)kg(-1.)min(-1)] who were participating in an Ironman triathlon, in random order: (1) cycled at their POThvent (Bi-Th,Bi-vent) until they were exhausted, and (2) cycled for 5 h at a self-selected intensity (Bi-SSI). Cycling power output (PO), oxygen uptake (V) over dot (O2))), heart rate (HR) and blood lactate concentration ([La-](b)) were recorded at regular intervals during these trials, while performance HR was recorded during the cycling phase of the Ironman triathlon. Significantly greater (P < 0.05) values were attained during Bi-Th,Bi-vent than. during Bi-SSI for PO [274 (9) compared to 188 (9) W], ((V over dot (O2))) [3.61 (0.15) compared to 2.64 (0.09) 1(.)min(-1)], and [La-](b) [6.7 (0.8) compared to 2.8 (0.4) mmol(.)1(-1)]. Moreover, mean HR during the Ironman triathlon cycle phase [146.3 (2.4) beats(.)min(-1); n = 7] was significantly greater than mean HR during Bi-SSI [130 (4) beats(.)min(-1)], and significantly less than mean HR during Bi-Th,Bi-vent [159 (3) beats-min(-1); all P <0.05]. However, HR during the cycle portion of the Ironman triathlon was highly related to (r = 0.873; P <0.05) and not I significantly different to HRTh,vent [150 (4) beats(.)min(-1)]. These data suggest that ultra-endurance triathletes cycle during the Ironman triathlon at a HR intensity that approximates to HRTh,vent, but at a PO that is significantly below POTh,vent.