Standardization of the Dmax method for calculating the second lactate threshold

Purpose: The purpose of this study was to test the reliability and validity of 2 standardized methods for calculating speed at the second lactate-threshold point (LTâ‚‚) based on the pre-existing Dmax (LTá´…) and modified Dmax (LTá´á´á´…) procedures. Methods: 13 trained male road runners and triathletes completed 2 incremental laboratory running tests to determine LTâ‚‚, followed by separate time trials (5, 10, 15 km) on an outdoor running track. Two new methods were proposed for calculating the speed at LTâ‚‚: (1) the single standardized lactate threshold (LTsdp) and (2) the paired standardized lactate threshold (LTsds) for quantifying changes over time. Results: The LTsds and LTsdp methods had high relative (ICC≥.98) and absolute (CV≤1.9%) reliability in identifying the speed at LTâ‚‚. The speed at LTâ‚‚ 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 (≤2.3%; Ïc ˃0.8; P ˃ .05). The following natural log-based formula was created to estimate the percentage of LTâ‚‚ speed (using the LTsds method) that could be sustained for events ~15-75 min: y=-7.256 (In x) + 157.64, where y=%LTâ‚‚ speed, x=time-trial performance (s), and In" natural log. Conclusions: The standardized methods are reliable for determining LTâ‚‚. The LTsds and LTsdp methods for calculating the speed at LTâ‚‚ 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 LTâ‚‚ that can be sustained for events of ~15-75 min was generated.