Running velocities and heart rates at fixed blood lactate concentrations in young soccer players

The purpose of this study was to examine the running velocities and heart rates at fixed lactate concentrations of young soccer players according to playing position and age. A total of 223 young male soccer players participated in this study. Each player performed incremental exercise tests on a treadmill. Running velocities and heart rates at 2 mmol/L-1, 2.5 mmol/L-1, 3 mmol/L-1, and 4 mmol/L-1 blood lactate concentrations were calculated with use of the spline function. Data were analyzed through analysis of variance to examine differences among various playing positions (ie, defenders, midfielders, and forwards) and 3 age groups (U17, under 17 y; U19, under 19 y; and U21, under 21 y). No significant differences were discerned between defenders, midfielders, and forwards in terms of running velocities and heart rates in accordance with specified lactate concentrations. Running velocities corresponding to all lactate concentrations showed no significant differences at all age groups, but heart rates in soccer players in the U21 and U19 age groups were significantly lower than in the U17 age group. Following a 3-y trial of 20 players, running velocities increased and heart rates decreased at all corresponding lactate concentrations. Results of this study suggest that (1) the endurance performance level of young soccer players is similar for all positions, and (2) heart rates are lowered with age and with training.