Comparison of modeled lactate threshold 2 with MLSS in running and cycling.

Abstract

The study investigated 1.The agreement of modeled lactate threshold 2 (_modLT2) using maximal oxygen uptake (V̇O_2peak),cost of locomotion (C), and fractional utilization of (V̇O_2peak) at LT2 (LT2_%) with maximal lactate steady state (MLSS) in running and cycling. 2.The impact of different C determination methods on the accuracy of the model. 3.The contributions of V̇O_2peak,C, and LT2_% to work rate at MLSS. Thirty-four endurance-trained athletes (27.7±6.9 yrs, 56.2±5.5 ml∙kg^-1∙min^-1) completed an incremental step test on a treadmill or cycling ergometer.V̇O_2peak,C at lactate threshold 1, 80% of V̇O_2peak and LT2 (C_LT2), and LT2_% were assessed.Two to five 30 min constant work rate tests were performed for MLSS determination. Moderate to good agreement was found between _modLT2 and MLSS for running and cycling (ICC ≥ 0.698) with the smallest mean difference (± limits of agreement) for C_LT2 with -2.0±5.2% and -0.9±6.0%, respectively.83% and 79% of the total variance of MLSS was explained by V̇O_2peak,C_LT2 and LT2_%, respectively.V̇O_2peak and C_LT2 contributed the most to the regression R² in running (54% and 40%) and cycling (74% and 51%), while LT2_% had the smallest contribution (4% and 5%). Based on the high accuracy of the model with the major contribution of V̇O_2peak and C_LT2, MLSS could be improved focusing on these two variables during training.