Influence of Ball Properties on Simulated Ball-to-Head Impacts

The risk of injury is an unfortunate reality in sporting events of all types and all levels of competition. In many sports, ball properties are held to strict standards to maintain high levels of consistency and performance. Quantitative knowledge of how materials affect player safety is important in the development of ball performance standards. To increase our understanding of the relationship between the properties of sports balls and the potential for player injury, we constructed a finite element model of ball-to-head impacts. Our simulations combined leading finite element models of softballs and the Total Human Model for Safety (THUMS). Frontal and lateral impacts to the head were simulated using two different ball models, and for initial ball velocities ranging from 26.8 m/s to 53.6 m/s. While the ball models were approved for the same level of play, their stiffness differed by 30%, resulting in up to a 63.7% difference in skull impact stress for the same impact conditions. The results show that injury severity is a strong function of ball material properties and can differ measurably with ball model, even with balls designed for the same level of play.