Standardisation of the Dmax method for calculating lactate threshold

Purpose: The purpose of this study was to test the reliability and validity of two standardised methods for calculating speed at the second lactate threshold point (LT2) based upon the pre-existing Dmax (LTD) and modified Dmax (LTMOD) procedures.\ud \ud Methods: 13 trained male road runners and triathletes completed two incremental laboratory running tests to determine LT2 followed by separate time-trials (5, 10, 15 km) on an outdoor running track. Two new methods were proposed for calculating the speed at LT2; 1) the single standardised lactate threshold (LTSDs), and 2) the paired standardised lactate threshold (LTSDp) for quantifying changes over time.\ud \ud Results: The LTSDs and LTSDp methods had high relative (ICC≥0.98) and absolute (CV≥1.9 %) reliability in identifying the speed at LT2. The speed at LT2 according to the LTSDs and LTSDp methods had a strong correlation and was not different to the performance speed during the 10 and 15 km time-trials (≥2.4 %; ρc>0.8; p>0.05). The following natural log-based formula was created to estimate the percentage of LT2 speed (using the LTSDs method) that could be sustained for events ~15-75 min: y= -7.256 (lnx) + 157.64 (y=%LT2 speed, x=time-trial performance [s], ln=natural log).\ud \ud Conclusions: The standardised methods are reliable for determining LT2. The LTSDs and LTSDp methods for calculating the speed at LT2 from a near-maximal incremental test calculated speeds similar to those exhibited in 10 and 15 km running time-trials. A prediction equation for estimating the percentage of LT2 that can be sustained for events of ~15-75 min was generated