Abstract
To assess the relationship of exercise test variables to each other and to bike race times in an ultra-distance triathlon, we studied 24 participants (14 men, 10 women) in the 1985 Hawaii Ironman Triathlon, using a graded, maximal cycle ergometer test with gas exchange and blood lactate (LA) measurements at each work load. Exercise test variables were oxygen uptake (V̇O2) and heart rate (HR) at the lactate and ventilatory thresholds. Lactate threshold (LT-1) was defined as the exercise intensity that elicited a 1 mM increase in blood lactate concentration above the value measured during the first work load for each subject. Variables were also examined at the lactate thresholds of 2 mM and 4 mM. Ventilatory thresholds (V̇T) were identified as the points at which the ventilatory equivalent of oxygen (V̇E/ V̇O2) increased without a corresponding increase in the ventilatory equivalent of carbon dioxide (V̇E/ V̇CO2). Mean peak oxygen uptake (peak V̇O2) for this sample of Ironman triathletes was 57.4 ml·kg-1 · min-1. Cycle peak V̇O2 was inversely correlated, r=-0.68 (P<0.0002) with bike finish time. V̇O2 and HR as well as the respective percentages of maximum were higher at all lactate thresholds than at V̇T (P<0.0001). Therefore V̇T should not be used to identify a lactate threshold in utra-endurance triathletes. V̇O2 values at the lactate and ventilatory thesholds were not highly related to bike finish time (r=-0.26 to -0.58). Fractional utilization of peak V̇O2 (% peak V̇O2), HR, and % peak HR at thresholds were not related to bike finish time (r=-0.01 to 0.06). Cycle peak V̇O2 and cycling economy (r=0.61) were related to bike finish time in an ultra-distance triathlon, but physiologic variables at lactate or ventilatory thresholds were not useful to the athlete in predicting performance.
Key words
lactate threshold - ventilatory threshold - peak V̇O2
- cycling economy - ultra-endurance exercise
