TIME TO EXHAUSTION AT VO2MAX AND LACTATE STEADY-STATE VELOCITY IN SUB ELITE 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 the 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 maximal speed (Va max) (21.6 +/- 1.2 km.h-1, CV 6%). The fractional utilization 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). The subjects ran twenty minutes at a constant velocity representing 70-75% and 85-90% VO2max. Lactatemia was measured at the fifth (Lact 5) and the twentieth minute (Lact 20). Lactate slope was measured for two running velocities in order to determine the velocity (WCL) corresponding to lactate steady state, i.e. the lactate slope is equal to zero. The main results showed that in the small and homogeneous sample of runners 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 time 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 expressed in % Va max (r = 0.775). Tlim at Va max was also related to WCL expressed in % VO2max (r=0.604) and to WCL expressed in % Va max (r=0.629). 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.