TIME TO EXHAUSTION AT VO2MAX AND LACTATE STEADY-STATE VELOCITY IN SUBELITE LONG-DISTANCE RUNNERS

The aim of the present study was to estimate the importance of lactate steady state velocity (WCL) of the running velocity at maximal oxygen uptake (Va max) and its time to exhaustion (Tlim), in the performance of a half marathon stated by the velocity over 21.1 km sustained by t he runners during 1 h 12 min +/- 2 min 27 s. The population consisting of ten sub-elite male long distance runners (32 +/- 4 years old) was homogeneous with regard to their velocities on 21 km (V21 = 17.5 +/- 0 .88 km.h-1, coefficient of variation, CV = 5 %) and their aerobic maxi mal speed (Va max) (21.6 +/- 1.2 km.h-1, CV 6%). The fractional utiliz ation of VO2max on 21 km was calculated from their own running economy (oxygen consumed per kilo of body mass and kilometer run (194 +/- 74 ml.kg-1.km-1). V21 represented 83 +/- 5% VO2max (VO2max = 68.1 +/- 4.1 ml.kg-1.min-1) and 81 +/- 3.3% Va max. The velocity corresponding to lactate steady state and called ''lactate steady state velocity'' (WCL ) was measured according to a protocol proposed by CHASSAIN (1986). Th e subjects ran twenty minutes at a constant velocity representing 70-7 5% and 85-90% VO2max. Lactatemia was measured at the fifth (Lact 5) an d the twentieth minute (Lact 20). Lactate slope was measured for two r unning velocities in order to determine the velocity (WCL) correspondi ng to lactate steady state, i.e. the lactate slope is equal to zero. T he main results showed that in the small and homogeneous sample of run ners studied, WCL (km.h-1) was related to V21 (km.h-1) (r=0.55, P<0.07 ); Va max (km.h-1 was related to V21 (km.h-1) (r=0.732, P<0.05)but tim e to exhaustion at Va max(6.11 +/- 2 min01 sec) was not related to V21 (km.h-1) (r = 0.27). However, Tlim at Va max was related to V21 expre ssed in % Va max (r = 0.775). Tlim at Va max was also related to WCL e xpressed in % VO2max (r=0.604) and to WCL expressed in % Va max (r=0.6 29). Tlim at Va max and WCL (expressed in % VO2max or in Va max) were both endurance indices but at maximal and submaximal intensities, WCL being more specific to half marathon intensity.