Determination of Blood Lactate Concentration: Reliability and Validity of a Lactate Oxidase-based Method

Int J Exerc Sci 2(2): 83-93, 2009. 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. Differences in blood lactate concentrations between the three methods were analyzed using ANOVA (a=0.05). Although all three experimental protocols yielded similarly shaped lactate curves, the actual values for the LDH method was significantly lower than the HPO and the YSI at every intensity level (bias p<0.05). We conclude that the HPO 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.