Laboratory and Field Studies in Sports-Related Brain Injury

The studies presented in this dissertation investigated biomechanical factors associated with sports-related brain injuries on the field and in the laboratory. In the first study, head impact exposure in youth football was observed using a helmet mounted accelerometer system to measure head kinematics. The results suggest that restriction on contact in practice at the youth level can translate into reduced head impact exposure over the course of a season. A second study investigated the effect of measurement error in the head impact kinematic data collected by the helmet mounted system have on subsequent analyses. The objective of this study was to characterize the propagation of random measurement error through data analyses by quantifying descriptive statistic uncertainties and biases for biomechanical datasets with random measurement error. For distribution analyses, uncertainties tend to decrease as sample sizes grow such that for a typical player, the uncertainties would be around 5% for peak linear acceleration and 10% for peak angular (rotational) acceleration. The third and fourth studies looked at comparisons between two headforms commonly used in athletic helmet testing, the Hybrid III and NOCSAE headforms. One study compared the headform shape, particularly looking at regions that are likely to affect helmet fit. Major differences were found at the nape of the neck and in the check/jaw regions that may contribute to difficulty with fitting a helmet to the Hybrid III headform. For the final study, the impact responses of the two headforms were compared. Both headforms were mounted on a Hybrid III neck and impacted at various magnitudes and locations that are representative of impacts observed on the football field. Some condition-specific differences in kinematic parameters were found between the two headforms though they tended to be small. Both headforms showed reasonable repeatability.