Simple kinetic model for the study of lactate metabolic adaptation to exercise in sportsmen routine evaluation

The interindividual specific lactate metabolic adaptation to exercise has been studied. A simple kinetic model was used which did not require labelled molecules. An one open compartment model with a first-order release rate constant described the release of lactate from the muscle. Six volunteers performed five times the same session: pedaling as long as possible at 400 W and 110 rpm. The lactate concentration was measured along the 60 min of recovery. The theoretical curve corresponding to the model was fitted to the experimental data using a non-linear regression method. The values of the following kinetic parameters were obtained: elimination rate constant (ke), release rate constant (ka), apparent amount released into the compartment divided by the volume of distribution (FQo/Vd) and area under the lactate concentration-time curve (AUC). Two way-ANOVA, Scheffé test and discriminant analysis were used to test the statistical significance of these parameters. No significant intra-individual variations were shown. Significant differences were observed between subjects (ke: P = 0.0020; ka: P less than 0.0001; FQo/Vd: P = 0.0002; AUC: P = 0.0395). A correlation was also found between FQo/Vd and ke (r = 0.72; P less than 0.001). In conclusion, the computed parameters provided by the model are sufficient to discriminate and characterize the metabolic response of each subject after short and intensive exercises.