Testing modality affects lactate threshold assessed with different methods

Aim: The lactate threshold (LaT) is an important physiological parameter in the laboratory and on the field. Continuous incremental ramp tests are commonly used for LaT determination (Bosquet et al. 2007). The aim of the study was to compare two incremental ramp tests on the treadmill, with different velocity increments in time and to determine to what extent protocol would affect LaT assessment. Moreover, we investigated also which of the five methods (DMAX, DMAX MOD, 4 mM, Δ1 mM and Log-Log) commonly utilized to assess LaT was less affected by differences in testing modality. Methods: Sixteen physically active males (age 22.5±1.8 yrs; stature 1.75±0.04 m; body mass 68.7± 4.0kg; mean±SD) reported to the laboratory on different days to perform two maximum incremental continuous ramp protocols (1 km⋅h-1 per min, R1, and 2 km⋅h-1 per min, R2), in random order. max and LaT were assessed on a motorised treadmill. At rest and during exercise, cardiorespiratory and metabolic parameters were collected breath-by-breath. Blood lactate concentration [La-] was measured at rest, during, and at peak exercise. In both protocols, LaT was calculated by DMAX, DMAX MOD, 4 mM, Δ1 mM and Log-Log methods. Results: LaT was found at significantly higher velocities in R1 vs R2 for DMAX (16.5±0.4 vs 15.1±0.4 km⋅h-1), DMAX MOD (17.7±0.5 vs 15.6±0.4 km⋅h-1), 4mM (17.0±0.6 vs 15.5±0.5 km⋅h-1), Δ1mM (17.1±0.5 vs 15.1±0.4 km⋅h-1), but not for Log-Log. Conclusions The testing modality influenced significantly LaT assessment. Indeed, with the only exception of Log-Log method, all the other methods for LaT determination presented significantly higher velocities at LaT when the steeper slope (R1) of the velocity vs time relationship was utilized. This was probably due to a delayed La- accumulation in R1 because of the insufficient time for La- equilibration between muscle and blood. Therefore, care must be taken with the protocol choice and the method used for LaT determination when precise assessments are needed.