Does size matter for sports performance researchers?

soccer. Our aim was to develop a mathematical model of the ballʹs flight incorporating aerodynamic lift and drag forces to explore this important ʹset-playʹ. Trajectories derived from the model have been compared with those obtained from detailed video analysis of experimental kicks. Representative values for the drag and lift coefficients have been obtained, together with the implied orientation of the ballʹs spin axis in flight. The drag coefficient varied from 0.25 to 0.30 and the lift coefficient from 0.23 to 0.29. These values, used with a simple model of a defensive wall, have enabled free kicks to be simulated under realistic conditions, typical of match-play. The results reveal how carefully attackers must engineer the dynamics of a successful kick. For a central free kick some 18.3 m (20 yards) from goal with a conventional wall, and initial speed of 25 m·s-1, the ballʹs initial elevation must be constrained between 16.5° and 17.5° and the ball kicked with almost perfect sidespin.