Lactate, Oxygen Uptake, and Cycling Performance in Triathletes

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