Arrival velocities for headers from corner kicks are comparable between modern and historic association footballs

Through different “eras of play,” association footballers have headed different types of footballs, in dry and wet conditions. With concern surrounding neurodegenerative disease development in footballers, much consideration is being given to heading impact severity, where inbound ball velocity is a key determinant. It is commonly hypothesised that modern ball types arrive at the head with significantly faster inbound velocities than historic counterparts. This study modelled a corner kick trajectory, which commonly precedes a header, using three different ball types, in both dry and wet conditions. Ball aerodynamic coefficients were attained through wind tunnel experimentation and were used to generate representative flight paths through a computational flight model with backspin, to determine the finite range of combinations of launch speeds, elevation angles, and spin rates for a given ball that resulted in corner kick trajectories that passed above the penalty spot, at a reasonable range of heights for heading interception. This study concluded that, between each ball type and condition, the inbound ball velocity was very similar. Launch conditions achieved by players had a greater influence on inbound velocity than the differences between ball type or wet conditions.