Investigation of the metabolic responses during the cycling phase of an ultraendurance triathlon

The purpose of this study was to investigate the premise that ultraendurance triathletes perform the cycling portion of the Ironman Triathlon at an intensity near ventilatory threshold (T[sub vent]). Eleven highly-trained ultraendurance triathletes ( x ± SEM: age = 35.8 ± 1.6 yrs; body fat = 11.7%; VO₂[sub max] = 67.5 ± 1.0 ml•kg⁻¹•min⁻¹) completed two randomly assigned trials. The first trial consisted of a ride to volitional fatigue (BiT[sub vent]) at the subjects Tv e nt power output (PO[sub Tvent]) calculated from a preliminary cycling V02 m a xtest. The second trial was a 5 h bike time trial at a self-selected pace (Bi[sub SSP])- The endurance time for the BiT[sub vent] was 130.7 ± 18.6 min. Significant differences between trials existed on the measures: power output = 273.6 ± 8.6 vs. 188.0 ± 8.6 W; VO₂ = 3.61 ± 0.15 vs. 2.64 + 0.09 Lmin⁻¹ ; % T[sub vent] VO₂ = 110.7 ± 2.6 vs. 80.5 ± 3.3%; HR = 159 ± 3 vs. 130 ±4 bpm; RER = 0.95 ± 0.01 vs. 0.91 ± 0.01; and V[sub E]= 103.4 ± 4.7 vs. 66.7 ± 2.8 Lmin⁻¹; BiT[sub vent] vs. Bi[sub SSP] respectively. While these results suggest that ultraendurance triathletes do not perform at their PO[sub Tvent] during the cycling phase, mean HR data (146 ± 2 bpm) from seven of these subjects during the bike portion of the Canadian Ironman Triathlon (IMC) demonstrate that ultraendurance triathletes do perform at an intensity near their T[sub vent] HR (150 ± 4 bpm; r = .873; p < 0.05). A treadmill run V₂[sub max] subsequent to Bi[sub SSP] significantly reduced T[sub vent]speed (8.9 ± 0.3 mph vs. 8.4 ± 0.2 mph; p < .05), however, did not improve the ability to predict IMC marathon run pace (IMC marathon = 5.9 ± 0.3 mph; r= .425; p > .05).Education, Faculty ofKinesiology, School ofGraduat