Modelling the Blood Lactate Response to Maximal Short Term Exercise with Elevated Starting Levels

Abstract

Recently a 3-parameter bi-exponential model was proposed (Beneke et al. 2005) as a means of calculating the blood lactate concentration (BLC) response to maximal short term exercise (MSE). It approximates an extravascular increase (A) of lactate generated by exercise metabolism during MSE, which is equivalent to the subsequent return to the pre-exercise lactate concentration, and two velocity constants describing the corresponding kinetics of the appearance (k1) and the disappearance (k2) of lactate into and out of the blood compartment. Conceptually the model requires warm up procedures that do not increase BLC at the start of exercise (BLC0) compared toresting conditions. PURPOSE: We developed a new 3-parameter bi-exponential model that considers an elevated BLC0, and analysed the effect of potential inappropriate application of the previous model on tests with elevated BLC0. METHODS: 9 subjects (26.9 ± 5.1 yrs, 1.83 ± 0.06 m, 80.7 ± 7.8 kg) performed 16 Wingate anaerobic Tests following a standardized warm up. RESULTS: BLC0 was elevated compared to pre warm up (1.5 ± 0.6 mmol l−1 vs. 1.0 ± 0.4 mmol l−1, p < 0.001). Compared to the new model, use of the original model decreased the explanation of the variance of the BLC response, k2 and the predicted time of the maximum BLC (96.7 ± 2.0 vs. 96.2 ± 2.0 %, 0.0252 + 0.007 vs. 0.0246 ± 0.07 min−1 and 6.0 ± 1.0 vs. 5.8 ± 0.9 min; all p < 0.001). Both, A and k1 increased (15.2 ± 1.5 vs. 15.6 ± 1.6 mmol l−1 and 0.56 ± 0.13 vs. 0.59 ± 0.14 min−1; both p < 0.001) whilst the predicted post-test maximum BLC was not different (14.5 ± 1.6 vs. 14.5 ± 1.6 mmol l−1; p > 0.05). CONCLUSION: The results indicate that inappropriate application of the original model on tests with elevated starting BLC levels results in a misinterpretation of the dynamics of the BLC response to MSE but the predicted post- test maximum BLC remains unaffected.