Maximal Fat Metabolism Explained by Lactate-Carbohydrate Model

(1) Background: Maximal fat oxidation (MFO), its associated exercise intensity (Fatmax) and the cross-over point (COP) are known indirect calorimetry-based diagnostics for whole-body metabolic health exercise. However, large inter- intra-individual variability in determining their corresponding makes use inconsistent, whether is based on power output or oxygen uptake. Blood lactate concentration (BLC) has often reflected a range MFO COP, which may offer another non-indirect calorimetry dimension near equilibrium between pyruvate at molecular level, biochemically determines an interchange relative rate of carbohydrate (relCHO) utilization (relFAO). This paper proposes new testing approach describing relCHO as function BLC, with individualized half-maximal activation constant (kel), to explain predict MFO, Fatmax COP. (2) Methods: Following ethical approval, twenty-one healthy males participated incremental cardiorespiratory maximal test, capillary BLC was measured. Indirect relFAO were calculated, kel that 50% CHO saturation level estimated sigmoid (mmol·L?1): = 100/(1 + kel/BLC2). (3) Results: 86% explained by levels. The estimations, 1.82 ± 0.95 (min/max 0.54/4.4) (mmol·L?1)2 independently 55% 44% COP variabilities. Multiple regression analysis resulted highest independent predictor (adjusted r-square 22.3%, p < 0.05), whilst classic intensity-based predictors (peak power, uptake, fixed 4 mmol·L?1) not significant predictors. (4) Conclusions: BLC-relCHO model, explains outs through dynamic changes carbohydrates regardless takes place. capability intensities provides diagnostic tool physiological performance.