Effect Of Sprint Duration On Blood Lactate Kinetics In Children, Adolescents And Adults

Abstract

A lower blood lactate concentration (BLC) response to maximal short-term high intensity exercise has been consistently reported in children compared to both adolescents and adults. Therefore, it has been proposed that pre pubertal children have a lower glycolytic rate compared with adolescents and adults. PURPOSE: The aim of the present study was to examine the effect of age on changes in BLC and rate of muscular lactate appearance (MLAR) as an indicator of net glycolytic rate under real track sprinting conditions of given durations. METHODS: 8 pre-pubertal boys (age: 10.4±0.3 yrs, height: 1.42±0.09 m, body mass: 36.1±9.7 kg) and 9 male adolescents (15.4±0.3 yrs height: 1.71±0.04m, body mass: 61.2±7.3 kg) and 8 male adults (20.6±0.7 yrs height: 1.81±0.03 m, body mass: 83.9±14.9kg) completed 3 maximal sprints: duration T1: 100m, 150m and 150m; T2: 140m. 190m and 210m and T3: 200m, 260m and 280m for children, adolescents and adults, respectively. BLC was measured pre-exercise and up to 30 minutes post-exercise. Data were analysed using a bi-exponential 4-parameter model including lactate increases in the extravascular space (A) and time constants describing the appearance and disappearance of lactate in the blood compartment. MLAR was calculated based on A and generally accepted assumptions of water space and relative muscle mass in children and adolescents. RESULTS: Test duration was not different (P>0.05) between the groups for each sprint (T1: 18.9±3.4vs. 21.6±2.1 vs. 21.8±1.2;T2: 27.7±5.1 vs. 28.2±2.6vs. 32.2±3.8;T3: 42.8±8.9vs. 42.0±3.1 vs. 45.4±2.8 s). There was a significant main effect for maximum BLC with respect to sprint duration and age (p < 0.05). However, no group difference in MLAR was found (P>0.05). MLAR decreased (p < 0.05) with each increase in sprint duration (T1: 0.91±0.21 vs. 0.99±0.24vs. 1.0±0.24; T2: 0.69±0.19vs. 0.83±0.27vs. 0.92±0.23;T3:0.56±0.21 vs. 0.56±0.12 vs. 0.70±0.14 mmol.kg-1.s-1) irrespective of age. CONCLUSIONS: The results demonstrate that in flat out sprints lasting approx. 20 to 45 s, age influences the magnitude of the post-exercise BLC as result of relative muscle mass and dilution space without relevant differences in muscular glycolytic rate.