Curvilinear sprint acceleration-speed profile in youth soccer players is constrained by tighter radii and sprinting side dominance

This study investigated how the acceleration-speed profile (ASP) of the weaker and stronger side changes at different radii. Twenty male youth soccer players completed 30 m linear and curvilinear sprints (12.15, 11.15, 9.15, 7.15, and 6.15 m radius) in three training sessions. Sprint speed and acceleration over time and distance were recorded using a GNSS device. The maximum theoretical speed (S₀), the acceleration (A₀), slope of the ASP (AS_slope), the area under the AS_slope (ASP_area), the acceleration at a sprint speed of 3 m/s (A₃), and the curvilinear sprint deficit (ASP_deficit) of the individual sprints were analyzed. The effects of side, radius, and their interaction were evaluated with 2 × 5 ANOVA and the post hoc tests. A significant effect of radius and side was observed for all variables (F ≥ 3.50, p ≤ 0.037, η² ≥ 0.15). The ASP_area and S₀ decreased at tighter radii. The A₃ and A₀ remained relatively unchanged, resulting in a steeper AS_slope, and a larger ASP_deficit. At the same radius, the weaker side CS had a smaller ASP_area, S₀, A₃, and a larger ASP_deficit. The ASP of the curvilinear sprint in youth soccer players is side-dependent at both ends (acceleration and top speed), while radii mainly affect late acceleration and top speed performance. These observations should be considered when adapting soccer players' sprint training and monitoring external load based on acceleration.