Concussions and changes in neurophysiology due to sub-concussive blows are common in contact sports, motivating a need for improved safety systems. While there have been attempts to determine whether or not new helmet designs influence the incidence of concussion, the results to date have been inconclusive. Consequently, the goal of this study was to evaluate the ability of modern football helmets to mitigate linear impacts directed normal, as well as oblique, to the surface of the helmeted head using a system that quantifies both the input load and the resulting accelerations of a Hybrid III headform. The transfer function connecting the inputs and outputs of the system was developed using dimensional analysis to provide a means of comparing helmets across brands and sports. For translational accelerations, increased helmet mass and a secondary layer of padding helped mitigate the impacts. The attenuation of angular accelerations depended substantially on helmet model and impact location.

It has been documented that up to 22% of all soccer injuries are concussions. This is in part due to players purposely using their head to direct the ball during play. To provide a more complete understanding of head trauma in soccer athletes, this study characterized the effects of four soccer ball characteristics (size, inflation pressure, mass, velocity) on the resulting peak impact force as it relates to the potential for incurring neurophysiological changes. A total of six hundred trials were performed on size 4 and 5 soccer balls as well as a novel lightweight soccer ball. Impact force was measured with a force plate and ball velocity was determined using motion capture. These data were used, in conjunction with dimensional analysis to relate impact force to ball size, mass, velocity, and pressure. Reasonable reductions in allowable ball parameters resulted in a 19.7% decrease in peak impact force. Adjustments to ball parameters could reduce a high cumulative peak translational acceleration soccer athlete down into a previously defined safer low loading range. In addition, it was noted that water absorption by soccer balls can result in masses that substantially increase impact force and quickly surpass the NCAA weight limit for game play. Additional research is required to determine whether varying soccer ball characteristics will enable soccer players to avoid persistent neurophysiological deficits or what additional interventions may be necessary and the legal implications of these data are discussed.

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