Lactate, respiratory compensation thresholds, and distance running performance in runners of both sexes.

To examine the possible gender differences in lactate threshold (LT) and respiratory compensation threshold (RCT) and their relations to running performance, ten male and eight female college distance runners performed an incremental running test on the level treadmill. Both groups of runners were matched as closely as possible on the basis of maximal aerobic power relative to lean body mass (VO2.max.LBM-1). LT, determined from an inflection point in blood lactate, was significantly higher in males than in females (49.2 vs 45.5 ml.kg-1 LBM.min-1 P less than 0.05), while RCT, determined from a marked increase in ventilatory equivalent for CO2 (VE.VCO2(-1], was not significantly different between the two groups (51.5 vs 52.3 ml.kg-1 LBM.min-1). No significant difference was observed either in LT or in RCT expressed as %VO2max. RCT and running velocity at RCT were strongly related to the run times of 800 and 1500 m in females and 5000 and 10000 min males (r = -0.76 approximately 0.95; P less than 0.05 approximately 0.001), while it was not the case with VO2max and LT. These results suggest that there are no remarkable gender differences in LT and RCT when compared in relative terms and that RCT is a sensitive parameter for evaluating an endurance performance despite its controversial status.