Curvilinear VO2: Power output relationship in a ramp test in professional cyclists: Possible association with blood hemoglobin concentration

Abstract

The purpose of this study was to determine (1) if there exists an additional, nonlinear increase (ΔVO2) in the oxygen uptake observed (VO2obs) at the maximal power output reached during a ramp cycle ergometer test and that expected (VO2exp) from the linear relationship between VO2 and power output below the lactate threshold (LT) in professional riders, and (2) the relationship between ΔVO2 and possible explanatory mechanisms. Each of 12 professional cyclists (25±1 years; VO2max: 71.3±1.2 ml· kg-1·min-1) performed a ramp test until exhaustion (power output increases of 25 W·min-1) during which several gas-exchange and blood variables were measured (including lactate, HCO3- and K+). VO2 was linearly related to power output until the LT in all subjects. Afterward, a nonlinear deflection was observed in the VO2:power output relationship (ΔVO2=-492±55 ml·min-1 and p< 0.05 for VO2obs vs. VO2exp). A significant negative correlation was encountered between ΔVO2 and resting hemoglobin levels before the tests (r=-0.61; p<0.05). In conclusion, professional cyclists exhibit an attenuation of the VO2 rise above the LT.