This study examined the influence of the regression model and initial intensity of an incremental test on the relationship between the lactate threshold estimated by the maximal-deviation method and the endurance performance. Sixteen non-competitive, recreational female runners performed a discontinuous incremental treadmill test. The initial speed was set at 7 km/h, and increased every 3 min by 1 km/h with a 30-s rest between the stages used for earlobe capillary blood sample collection. Lactate-speed data were fitted by an exponential-plus-constant and a third-order polynomial equation. The lactate threshold was determined for both regression equations, using all the coordinates, excluding the first and excluding the first and second initial points. Mean speed of a 10-km road race was the performance index (3.04 ± 0.22 m/s). The exponentially-derived lactate threshold had a higher correlation (0.98 = r = 0.99) and smaller standard error of estimate (SEE) (0.04 = SEE = 0.05 m · s-1) with performance than the polynomially-derived equivalent (0.83 = r = 0.89; 0.10 = SEE = 0.13 m/ s). The exponential lactate threshold was greater than the polynomial equivalent (P < 0.05). The results suggest that the exponential lactate threshold is a valid performance index that is independent of the initial intensity of the incremental test and better than the polynomial equivalent.
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