Poster P15 - Assessing the ability of current men’s and women’s lacrosse helmets to manage impact energy based on helmet liner thickness.

Introduction: Lacrosse is a popular men’s and women’s team sport that saw a 226% increase in participation between the years 2001-2017. Despite both men’s and women’s lacrosse athletes wearing some form of protective head equipment, 16% of all youth lacrosse injuries were diagnosed concussions, resulting in a higher yearly mean concussion incidence per 100,000 players than youth football. While women’s lacrosse is labeled as a non-contact sport with no headgear requirements (with a few exceptions), women’s lacrosse players experience concussions at a similar rate to their male counterparts (4.99 and 5.44 concussions per 10,000 athletic exposures for women’s and men’s respectively). However, female players who wear headgear have a 59% reduction in the overall incidence of concussion compared to athletes that do not wear headgear, emphasizing the importance of helmets in lacrosse. Therefore, this study aimed to evaluate helmet performance of currently available men’s and women’s lacrosse helmets and identify the design characteristics that could influence their performance. These results could be used to further guide lacrosse helmet design to improve lacrosse athletes’ head protection.

Materials and

Methods: All commercially available lacrosse helmets at the time of the study, including six men’s and two women’s helmets, were outfitted on a 50th percentile male NOCSAE headform and a Hybrid III neck on a sliding mass. Impact tests were performed on the helmeted headform using a pendulum with a round impactor face at two locations (front, side) and two energy levels (3.1, 5.2 m/s) informed by real-world data (Figure 1). Two helmet samples and two trials per sample were used for each testing configuration for a total of 128 tests. The NOCSAE headform was instrumented with a six-degree-of-freedom sensor package at its center of gravity. Data were collected at a sampling rate of 20 kHz and filtered using a 4-pole Butterworth low-pass filter with cut-off frequencies of 1650 Hz for accelerometer signals and 256 Hz for angular rate sensor signals. For each test, resultant peak linear accelerations (PLA) were recorded, and resultant peak rotational accelerations (PRA) were calculated by differentiating the angular velocity data using a five-point central difference method. After impact testing was performed, the impact center for each location was marked on the helmet, and the liner thickness at each location was measured (Table 1). A linear mixed effects model with helmet model as a random effect was conducted to quantify the effects of sex, liner thickness, impact speed, and impact location on PLA and PRA.

Results, Conclusions, and Discussions: A wide variety of helmet performances were observed across helmet models (Figure 2). Impact speed had strong effects on both PLA (p < 0.001) and PRA (p < 0.001). While impact location had an effect on PRA (p = 0.017), with the side location having higher rotational accelerations, there was no strong evidence of an effect on PLA (p = 0.170). Every one mm increase in the liner thickness caused an average 4.2 g decrease in PLA (p < 0.001) and a 174 rad/s2 decrease in PRA (p < 0.001) (Figure 3). Overall, we found that lacrosse helmets that maximized liner thicknesses performed better. Sex had strong effects on PLA (p = 0.015) and had some effect on PRA (p = 0.063), with men’s helmets being associated with 44.2 g lower PLAs and 1654 rad/s2 lower PRAs than women’s helmets. The large disparity between sex-specific models is likely due to intentional helmet design decisions. Men’s lacrosse helmets typically have a rigid plastic shell to protect against full-body contact that may occur during aggressive play, while women's helmets are constructed out of a softer plastic material or foam. This is primarily done to protect against lower-speed stick and ball impacts and prevent injury to athletes not wearing a helmet during unintentional contact, resulting in a worse performance at high-speed impact configurations than men’s helmets. Due to the high-contact nature of men’s lacrosse, increasing the liner thickness is especially important to protect against high-energy head impacts. While women’s lacrosse helmets perform similarly to men’s during low-speed impacts, future design decisions should consider ways to improve helmet performance during high-energy head impacts.

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