LAUSR

Objective The purpose of this study was to investigate the difference between arterialized and venous blood lactate concentrations [La] during constant-load exercises at different intensities. Methods Fifteen physically active men cycled for 30 minutes (or until exhaustion) at the first lactate threshold (LT1), at 50% of the difference between the first and second lactate threshold (TT50%), at the second lactate threshold (LT2), and at 25% of the difference between LT2 and maximal aerobic power output (TW25%). Samples of both arterialized and venous blood were collected simultaneously at rest and every 5 minutes during the exercise. Results The arterialized blood [La] was higher at minute 5 than venous blood [La] for all exercise intensities (p < 0.05). After this period, the arterialized and venous [La] samples became similar until the end of the exercise (p > 0.05). The arterialized-venous difference during the first 10 minutes was greater for the two highest exercise intensities (LT2 and TW25%) compared with the two lowest (LT1 and TT50%, p < 0.05). Thereafter, arterialized-venous difference decreased progressively, reaching values close to zero for all exercise intensities (p > 0.05). Conclusion These results suggest a delayed lactate appearance in the venous blood, which is accentuated at higher exercise intensities. The lactate measured in arterialized and venous blood is interchangeable only when blood samples are collected at least 10 minutes after the exercise starts.