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Characterization of the Biomechanical and Situational Aspects of High Magnitude Subconcussive Impacts in Collegiate Football.

OBJECTIVE
The objective of this study was to characterize high magnitude subconcussive impacts in football to identify injurious relationships between player/game-based characteristics and impact magnitude and frequency.


BACKGROUND
Subconcussive impacts are asymptomatic head impacts thought to induce alterations in the brain after repetitive exposure. Understanding factors that lead to higher magnitude or frequency of head impacts in football is crucial to develop harm reduction and prevention strategies.


DESIGN/METHODS
Eighty-one male university level football players were equipped with helmet accelerometers to capture linear acceleration (LA), impact frequency and helmet impact location. Impacts with LA = 60 g were included in the analysis. Video footage from 15 games over three seasons was analyzed to characterize aspects of play including play type, position, closing distance, player technique, tackling versus blocking and impact type (helmet-to-helmet/body/ground).


RESULTS
A total of 570 impacts were included in the analysis with a mean LA of 83.44 g ± 23.60. Impacts with a closing distance of = 10 yards resulted in higher LA compared to <10 yards and occurred most frequently in run plays. Wide receivers and defensive backs were most often involved in impacts with a larger closing distance and experienced the highest average LA behind quarterbacks. Helmet-to-body impacts generated significantly higher LA compared to helmet-to-helmet, though helmet-to-helmet occurred more often. Players involved in a tackle sustained significantly higher LAs than those involved in a block. Impacts in which players exhibited poor technique lead to higher LA and occurred more frequently in tackling versus blocking impacts.


CONCLUSIONS
The results of this work suggest that rules regarding offensive backfield running starts could be adjusted to decrease risk of impact after a larger closing distance. Behavioral modifications and coaching approaches aimed at improving tackling technique could decrease exposure to threshold impacts at the level of the individual player.