I am well aware of the methodology for determining lactate threshold; that is not my question. My doubts concern the physiology of lactate transportation to the blood. Once lactate is formed in the muscle, it takes a few minutes for it to enter the bloodstream. After high-intensity exercise, the highest levels of lactate in the blood are reported within a few minutes of rest. So, how can we accurately determine lactate threshold, considering this delay? For example, if we measure lactate at 2, 4, 6, 8, 10, and 12 minutes during a graded exercise test (GXT), assuming a 4-minute delay in lactate appearance in the blood for simplicity, the measurement at minute 4 would represent the starting point. The measurement at minute 6 would reflect minute 2, the measurement at minute 8 would represent minute 4, and so on.

Therefore, the actual lactate threshold (measured as the intensity of exercise) should be determined earlier during the GXT. For instance, if we determined the lactate threshold at 12 minutes (corresponding to 70% VO2max), assuming a 4-minute delay for this example, at the muscular level, it was at the 8th minute of the GXT. The intensity at the 8th minute was lower (approximately 60% VO2max). Consequently, there is a discrepancy between the lactate threshold measured at the blood level (70% VO2max at 12 minutes) and the muscular level (60% VO2max at 8 minutes). The challenge lies in determining which value, 70% or 60% VO2max, accurately represents the lactate threshold for this individual.