Table. Head Impact Exposure per Player in the Preseason vs Regular Season and in Football Practices vs Games.
| Exposure type | Median (IQR) | Estimated meana (95% CI) | P value |
|---|---|---|---|
| Weekly exposures | |||
| Preseason | 36.0 (14.0-66.3) | 46.9 (45.1-48.6) | <.001 |
| Regular season | 25.0 (10.0-48.0) | 32.4 (30.7-34.0) | |
| Season-long exposures (regular season) | |||
| Practices | 175.0 (76.0-340.5) | 243.2 (230.8-255.7) | <.001 |
| Games | 95.0 (32.0-206.0) | 138.3 (125.3-151.3) |
Abbreviations: HIE, head impact exposure; IQR, interquartile range; LMM, linear mixed model.
Estimated means and 95% confidence intervals from the LMM estimation. Comparison of exposure was conducted by regressing the average daily HIE per team per season on the preseason vs season binary variable: 66.7% in preseason and 33.3% in regular season (P value for the difference between preseason and season <.001). Preseason was defined as the period from the first day of football training through the last day of the week before the week of first scheduled regular season football game; regular season was defined as the period from the first day of the week leading up to the first scheduled game throughout the last day of the regular season. Using these parameters, preseason and regular season are nonoverlapping. Preseason includes practices and intrasquad scrimmages. Regular season includes practices, intrasquad scrimmages, and games.