MECHANISM OF LACTATE ACCUMULATION DURING THE LACTATE MINIMUM' TEST

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1857 The purpose of this study was to critically appraise the assumption of Tegtbur et al. (1993) that the lactate minimum test represents the individual equilibrium between lactate production and removal. This was investigated through simultaneous measurement of blood lactate, blood pyruvate and resulting lactate / pyruvate concentration ratio (L / P). Ten endurance trained subjects (5 male and 5 females) performed three exercise tests on a motorised treadmill: 1) an incremental test to determine lactate threshold(Tlac); 2) two supramaximal sprints at 120% ˙VO2 max velocity with 30 minutes passive recovery; 3) a lactate minimum(Lacmin) test according to Tegtbur et al. (1993). Fingertip capillary blood samples were taken for blood lactate and pyruvate concentration every 5 minutes in the incremental test and Lacmin test; and every 3 minutes during the passive recovery test. The velocity at Lacmin (Vlac min) was significantly lower than the velocity at Tlac (12.0± 0.4 km.h-1 vs 12.4 ± 0.5 km.h-1, P<0.05). In test 1, both blood [lactate] and L / P showed a sudden increase at the same velocity, [pyruvate] increasing one stage later. In test 2, both [lactate] and[pyruvate] showed an exponential decay (y = 5.64e-0.031, R2=0.99). In test 3, following the sprints, both [lactate] and[pyruvate] were elevated, but L / P remained at a similar value to rest (10.3± 1.0), decreasing in the incremental stages (to 5.6 ± 1.1 in increment 1). The L / P continued to decrease to the point of Vlac min presumably as a consequence of the slower disappearance rate of pyruvate compared to lactate. Pyruvate concentration in the Vlac min test was elevated above that at the same time in the recovery condition (0.32 ± 0.01 mmol.l-1 vs 0.28 ± 0.01 mmol.l-1 at minute 20). The maintained [pyruvate] elevation may partly explain the apparent discrepancy between Vlac min and Tlac.