Biomechanicl factors in mild traumatic brain injuries based on american football and soccer players

The complete biomechanical assessment of head impact includes not only investigations on players' head kinematics and brain tolerances, but also improvements in the design of protective headgear for head impact sports. Although these issues have been studied, there are related areas that have not been addressed in the literature. The purpose of this paper is to address some of the related issues and to demonstrate their relevance. The objectives of this study were 1) to quantify the brain injury likelihood for the struck players in an American football game and 2) to determine the effect of shock attenuating material, with different shear moduli, on the brain tissue deformation in head impact sports. An analysis was performed based on a subset of original National Football League (NFL) data for struck players only. The univariate analysis for each biomechanical parameter and the injury risk curves for selected biomechanical parameters were determined. Characteristics of the helmet material were assessed using a finite element (FE) elliptical head model. Cumulative strain damage measure (CSDM) data sets, corresponding to the strain levels of 0.01, 0.02, and 0.03, were utilized. Injury risk curves for HIC, SI, peak translational acceleration and peak rotational acceleration indicated a significant difference between the struck NFL players and analysis based on of all of the players. For all studied biomechanical parameters, injury risk was higher for struck NFL players. The percentage of reduction in brain volume, experiencing the strain level of 0.03, was reduced with the decrease of shear moduli. The highest reduction (24%) can be seen with the lowest shear moduli of 2.0 MPa. Injury risk is higher for struck NFL players in comparison to the striking players. For helmeted struck players, the threshold of brain injury risk is suggested as HIC-110, SI-130, peak translational acc-55 g; and peak rotational ace.-3300 rad/s ². The headgear made of shock attenuating material, with low shear moduli, can reduce the strain on brain tissue for players of head impact sports.