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Abstract
Statement of the Problem: Previous research has focused on mitigating head impacts to improve sport safety through rule changes and enforcing tackling techniques. However, there is limited information on pre-season factors that could be modified to further reduce head impact severity. We aimed to predict head impact biomechanics on factors such as: (1) head protection time, (2) cervical strength, and (3) anthropometric characteristics and helmet dimensions. Methods: Twenty-seven youth tackle football players (age=12.2±0.4yrs, height=161.5±9.7m, mass=55.5±15.2kg) participated in this study. Participants completed a pre-season protocol to analyze all objectives. The first objective included a motion capture analysis of a head protection reaction time and eye movement time protocol during a single- and dual-task performance using a light stimulus. The head protection time consisted of a player strategy, head turn, and hand reaction time (s) while eye movement time (s) was recorded using videography. The second objective used a Multi-Cervical Unit to assess cervical isometric strength (N/kg) and time to peak (s) in flexion, extension, left and right lateral flexion. We also captured time to peak in all 4 directions. The third objective captured anthropometric characteristics and helmet dimensions. We used univariate linear regression model with random intercepts to determine if there were associations between our predictors and head impact outcomes. We also performed separate linear regression models to determine the association of predictors and number of impacts.
Results: Our results from the first aim suggests slower eye movement time is associated with an increase in rotational velocity. Our results for aim two indicated stronger cervical strength in the left and right lateral flexion were associated with decreased peak rotational velocity. Slower time to peak left lateral flexion was associated with increased linear acceleration. Lastly, slower time to peak flexion and extension were associated with increased rotational velocity. For our third aim we discovered several anthropometric characteristics and helmet dimensions to influence head impact severity and frequency.
Conclusions: Several factors were found to be associated with increased head impact frequency and severity. Our study found potential modifiable factors, interventions, and designs to improve sport safety and mitigate head impacts among youth players.