BACKGROUND: Girls' lacrosse headgear that met the ASTM International performance standard (ASTM F3137) became available in 2017. However, the effects of headgear use on impact forces during game play are unknown. PURPOSE: To evaluate potential differences in rates, magnitudes, and game-play characteristics associated with verified impacts among players with and without headgear during competition. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 49 female high school participants (mean age, 16.2 ± 1.2 years; mean height, 1.66 ± 0.05 m; mean weight, 61.2 ± 6.4 kg) volunteered for this study, which took place during the 2016 (no headgear; 18 games) and 2017 (headgear; 15 games) seasons. Wearable sensors synchronized with video verification were used. Descriptive statistics, impact rates, and chi-square analyses described impacts and game-play characteristics among players with and without headgear. Differences in mean peak linear acceleration (PLA) and peak rotational velocity (PRV) between the no headgear and headgear conditions were evaluated using a linear generalized estimating equation regression model to control for repeated within-player measurements. RESULTS: Overall, 649 sensor-instrumented player-games were recorded. A total of 204 impacts ≥20g recorded by the wearable sensors were verified with video analysis (102 no headgear; 102 headgear). Most impacts were imparted to the player's body (n = 152; 74.5%) rather than to the player's head (n = 52; 25.5%). Impact rates per player-game did not vary between the no headgear and headgear conditions (0.30 vs 0.34, respectively; impact rate ratio, 0.88 [95% CI, 0.37-2.08]). There was no association between impact frequency by mechanism or penalties administered between the no headgear and headgear conditions for overall or direct head impacts. The generalized estimating equation model estimated a significant reduction in mean impact magnitudes overall (PLA: -7.9g [95% CI, -13.3 to -2.5]; PRV: -212 deg/s [95% CI, -359 to -64]) with headgear relative to no headgear. No game-related concussions were reported during this study. CONCLUSION: Lacrosse headgear use was associated with a reduction in the magnitude of overall impacts but not a significant change in the rate of impacts, how they occur, or how penalties were administered for impacts sustained during competition. Further research is needed with a larger sample and different levels of play to evaluate the consequences of headgear use in girls' lacrosse.
