No Difference in Blood Lactate and Pyruvate Combustion at Aerobic Performance in Boys and Adolescents

Abstract

The blood lactate concentration (BLC) reflects the combined effect of whole body glycolytic rate and pyruvate combustion. At termination of an exhausting incremental load test the BLC (BLCpeak) is lower in children than in adolescents. However, during prolonged constant exercise at the transition from the heavy to the severe intensity domain both BLC and exercise intensity are independent of age. The latter is not fully understood. Pyruvate is an activator of the pyruvate dehydrogenase complex regulating the relative rates of pyruvate combustion (RPY). PURPOSE: To test the hypothesis that up to the transition from the heavy to the severe intensity domain, BLC and RPY are similarly regulated in children and adolescents. METHODS: 11 pre-pubertal boys (median (25%-/75%-percentiles); 11.7(11.4/12.0) yrs, 1.51(1.49/1.56) m, 38.0(35.9/41.2) kg) and 11 male adolescents (17(16/17) yrs, 1.83(1.76/1.85) m, 68.0(63.0/71.1) kg) performed an incremental cycle ergometry. BLC was measured at the end of each 2 min stage (increment 0.5 Wkg-1) and after test termination. Oxygen uptake and carbon dioxyd production was determined for each stage for the indirect determination of RPY at RQ values below 1.0. RPY was individually described as a function of the BLC (RPY = 100 / (1 + kel/BLC2), where kel is the half maximal constant of RPY. RESULTS: The BLCpeak was lower (p < 0.05) in the boys (8.6(8.1/10.1) mmol 1-1) than in the adolescents (11.9(11.5/12.7) mmol 1-1). The kel was not different between boys (1.03(0.71/1.33) (mmol 1-1)2) and adolescents (1.11(0.74/1.80) (mmol 1-1)2). RPY was not different at any intensity, whilst at intensities above 75 % of peak power the BLC was higher (p < 0.05) in the adolescents than in the boys. CONCLUSION: The results indicate that RPY is similarly regulated in boys and adolescents which results in an almost identical BLC response at given exercise intensities up to the transition from the heavy to the severe intensity domain. At severe and maximal exercise intensities adolescents have higher levels of BLC.