The aim of this study was to investigate head impact doses in American football.  We analyzed time-synchronized video and data collected during n=445 player-games of  American football resulting in 2851video-verified impacts.  Cases where a player sustained impacts and on video was demonstrably witnessed to meet the NFL’s “No-go” criteria were analyzed in-depth.  

In 2011, after reviewing scalar on-field kinematics data leading concussion clinicians concluded “Recent studies suggest that a concussive injury threshold is elusive, and may, in fact, be irrelevant when predicting the clinical outcome”.¹  It is likely that higher fidelity estimates of spatial and temporal impact parameters will clarify the currently unclear impact dose-response relationship.

A total of 2851 video-verified head impacts were identified from 445 player-games. Each event was time-synchronized to video. Any events collected when the athlete was not being impacted in the head were discarded.  The remaining true positive events were scrutinized based on published methods to confirm a head impact occurred in the video and the computed motion was physically realistic and matched the video.⁷

We found a median of 5 video-verified head impacts per player-game, which is far fewer than published studies without video verification.¹¹ 

For the four players with “No-go” impacts, all were to the side/rear.  Coronal plane impact sensitivity has been a hypothesized clinical injury mechanism¹² and our results support that hypothesis.  

We did not see high PLA/PAA impacts without obvious player “No-go” observations.  This finding disagrees with other studies that have reported high PLA/PAA impacts without any demonstrable “No-go” observations¹³.

High energy impacts to the side and rear of the head are more damaging than similar magnitude impacts to the forehead.  Armed with this knowledge, clinicians should have more fidelity in their understanding of real-time impact location and severity, and how it relates to athlete concussion risk.