Polynomial modeling for the identification of lactate minimum velocity by different methods

摘要

The lactate minimum (LM) protocol has been used to assess aerobic fitness and to predict exercise intensity associated with the maximal blood lactate steady state. The aim of this study was to compare different methods to identify the lactate minimum velocity (LMV) on cycling. Fourteen male cyclists (26.8±4.5 years; 173.2±6.1 cm; 67.3±5.2 kg; 5,8±2.9 years of training) performed the LM test in a velodrome. The protocol consisted of an all out 2 km time trial to elevate blood lactate (bLAC), followed by 8 min of recovery and then 6 bouts of 2 km starting 5 km*h^sup -1^ below the individual mean velocity for the 6 km performance. The velocity was incremented by 1 km*h^sup -1^ at each bout with 25 µL of capillary blood being collected for bLAC measurements (YSI 2700 STAT). The LMV was identified visually (vLMV), and by applying a second grade polynomial function on 6 (pLMV^sub 6^) and 3 (pLMV^sub 3^) incremental bouts. Additionally, a method where the bLAC*work velocity^sup -1^ quotients (LMVQ) were plotted against the correspondent velocity during the incremental test, identified the LMV by considering 6 (LMVQ^sub 6^) or 3 bouts (LMVQ^sub 3^). Results. ANOVA showed no differences between vLMV (33.1±2.5 km*h^sup -1^), pLMV^sub 6^ (32.9±2.5 km*h^sup -1^), pLMV^sub 3^ (33.2±2.3 km*h^sup -1^), LMVQ^sub 6^ (32.8±2.5 km*h^sup -1^) and LMVQ^sub 3^ (33.4±2.3 km*h^sup -1^), with high correlation among them. It was possible to identify the LMV by the methods proposed in the present study, even when the results of only 3 bouts of the test were modeled by polynomial function. Such an approach enables a more practical and economical test in addition to minimizing the discomfort due to several blood collections.