Blood lactate concentrations and kinematic behavior of young runners in 50 and 100m sprints

Abstract

The purpose of this study was to verify the kinematic behavior of young runners during 50 and 100m sprints and their blood lactate concentration at the end of these sprints. Kinematic analysis was performed on the speed curve and some variables analyzed at the end of these runs. Fourteen individuals took part in this study, being 7 males (12.35 ± 0.83 years) and 7 females (12.61 ± 0.70 years). The speed curve was constructed using the panning method. The remaining kinematic variables were measured using two-dimensional videography with a Peak Motus video camera operating at 180 Hz. Blood samples were taken from the runners’ earlobes in order to assay lactate concentration. The results demonstrate that at both distances top speed is reached at 40m. This, however, corresponds to 80% of the distance of the 50m sprint, but just 40% of the 100m run. The significant differences in kinematic variables observed between the two sprints were: increased duration of the support phase in the males, decreased stride frequency among the females and lower average speed at the end of 100m in comparison to 50m, in all individuals. The highest blood lactate concentrations were observed after the 100m run. It was concluded that there was greater loss of performance during 100m, based on the differences between some kinematic variables and the major loss of speed. Moreover, despite lactate concentration being higher after this run, the values were still considered low, indicating a lack of anaerobic capacity in these individuals.