A model to predict maximal lactate steady state

Abstract

Maximal lactate steady state (MLSS) is an important measure of athletic performance. It is defined as the highest intensity of a constant load exercise that elicits an equilibrium between lactate accumulation and removal. Currently no consensus exists regarding the test duration of MLSS, or the criterion change in [BLa⁻] that constitutes MLSS. Theoretically the attainment of MLSS could be mathematically defined as a slope of zero when [BLa⁻] or [HCO₃⁻] is expressed as a function of time. The aim of this study was to compare: (i) the observed MLSSw to the slope model predicted MLSSw; (ii) the observed MLSSw to the lactate minimum power output (LMPO); and (iii) the finger and catheter [BLa⁻]. Twenty-three male trained cyclists performed an incremental V˙O_2max test to determine maximum aerobic power (MAP) (mean MAP = 5.2 W•kg⁻¹ and V˙O_2max = 58.3 ml•kg⁻¹•min ⁻¹) a lactate minimum test to determine LMPO and two to three 20-45 min constant load rides. Finger blood samples and venous blood from an indwelling catheter were sampled every 5 min during the constant load rides and analysed for [BLa⁻] and [HCO₃⁻ ]. The proposed models were: (a) (%MLSSw = 45.356*[BLa ⁻] slope + 100.62) catheter [BLa⁻] ; (b) (%MLSSw = −44.759* [HCO₃⁻ ] slope − 100.19) catheter [HCO₃⁻ ]; and (c) (%MLSSw = 46.353*[BLa⁻] slope + 100.35) finger [BLa⁻]. The 95% limits of agreement between the observed and slope model predicted MLSSw were (a) 2.3 ± 8.9 W; (b) 2.8 ± 9.3 W; (c) 1.7 ± 10.5 W and −1.4 ± 22.8 W for LMPO, no significant differences were found (p<0.05). Calculated MLSSw was defined as the x intercept of the power output versus slope relationship for each participant. Mean values of [BLa⁻] and [HCO₃⁻] at the observed MLSSw (252 ± 27 W) were (a) 4.7 ± 1.3 mmol•L ⁻¹; (b) 20.8 ± 1.3 mmol•L⁻¹; and (c) 4.7 ± 1.2 mmol•L⁻¹. No significant differences were noted between the finger and catheter [BLa⁻ ] (p<0.05). These findings suggest that given MAP the models could be used for predicting MLSSw in trained cyclists from a single constant load ride above MLSSw.