314 Heading a soccer ball and the characterization of parameters that influence its peak impact force

Background As participation in soccer increases in the United States, with an estimated 16 million registered players, the possibility of athletes being exposed to injuries, more specifically traumatic brain injuries, increases as well. All levels of soccer play have been associated with a high risk of TBI, predominantly through the mechanism of injury known as heading. Objective This study aims to model impacts between a soccer ball and head to determine what factors are most influential during a heading action. Design Dimensional analysis was utilized as a means to construct a model that would define the peak impact force as a function of four variables of interest: pressure inflation, incoming ball velocity, mass and diameter of a soccer ball. To characterize the model, a soccer ball was kicked at a force platform, while varying the ball size (size 4, 4.5 and 5) and pressure at which it was inflated (4, 8, 12 and 16 PSI). Main outcome measurements A Cotter’s method sensitivity analysis was used to determine which factors were most influential under the constructed model. Results Velocity and inflation pressure were found to be the most influential factors affecting peak impact force. In addition, a direct relationship was found between the force and velocity; the force and ball size and; the force and inflation pressure. Moreover, by controlling these parameters it is possible to reduce the amount of cumulative impacts a player receives in-game to a range at which the risk of TBI is much lower. These include lowering the pressure from 16–8 PSI, utilizing a smaller sized ball and reducing the number of impacts per season. Conclusions The model proposed determined that a reduction of injury risk due to TBI in soccer is possible through the control of specific in-game factors such as ball inflation pressure and controlling the number of impact events.