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Abstract

The measurement of blood lactate has long been used as marker of exercise intensity and training status. We compared a commercially available lactate oxidase spectrophotometric method (LO) to determine blood lactate levels to two previously validated methods, the lactate dehydrogenase spectrophotometric method (LDH), and the YSI 1500L Sport lactate analyzer (YSI). First we established a series of calibration curves over physiological range of lactate values (1-15 mM∙l-1 for the spectrophotometric assays and 1-30 mM∙l-1 for the YSI) with high correlations (0.986 < r < 0.999). Aerobically trained participants (n = 11) performed repeated exercise bouts of varying intensities on a cycle ergometer. Capillary blood samples (n = 189) were collected from the earlobe and the blood lactate concentration was determined using each of the three methods. An ANOVA (alpha=0.05) revealed no differences in blood lactate concentrations between the three methods. The three experimental protocols yielded similarly-shaped lactate curves, although the actual values for the LDH method was somewhat lower than the LO and the YSI at every intensity level. Bland-Altman plots revealed a slight bias towards lower lactate values with the LDH method, perhaps indicative of a more conservative measure of blood lactate. We conclude that the LO method is a reliable and valid method to determine blood lactate concentrations spectrophotometrically. All three methods can provide useful within-subject lactate curves, although we caution against interchangeable use of the three methods.

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