Curvilinear VO(2):power output relationship in a ramp test in professional cyclists: possible association with blood hemoglobin concentration.

The purpose of this study was to determine (1) if there exists an additional, nonlinear increase (DeltaVO(2)) in the oxygen uptake observed (VO2 (obs)) at the maximal power output reached during a ramp cycle ergometer test and that expected (VO2 (exp)) from the linear relationship between VO(2) and power output below the lactate threshold (LT) in professional riders, and (2) the relationship between DeltaVO(2) and possible explanatory mechanisms. Each of 12 professional cyclists (25 +/- 1 years; VO(2 max): 71.3 +/- 1.2 ml x kg(-1) x min(-1)) performed a ramp test until exhaustion (power output increases of 25 W x min(-1)) during which several gas-exchange and blood variables were measured (including lactate, HCO(3)(-) and K(+)). VO(2) was linearly related to power output until the LT in all subjects. Afterward, a nonlinear deflection was observed in the VO(2):power output relationship (DeltaVO(2) = 2492 +/- 55 ml x min(-1) and p < 0.05 for VO2 (obs) vs. VO2 (exp)). A significant negative correlation was encountered between DeltaVO(2) and resting hemoglobin levels before the tests (r = 20.61; p < 0.05). In conclusion, professional cyclists exhibit an attenuation of the VO(2) rise above the LT.