Impact Mitigation Properties and Mechanical Material Characterization of Women's Lacrosse Headgears at Ambient and Cold Temperatures

Abstract

The rate of concussion in women’s lacrosse is alarmingly high despite the sport being non-contact. Conflicting opinions on the potential effectiveness of helmet use in the sport led to the development of an ASTM standard in 2015 for optional headgear. These headgears are unique to most other head protection in that they do not have a hard outer shell because it could endanger players that choose not to wear the optional headgear. Because these headgears are so new and have unique design constraints, there is still much to learn about their ability to protect the players wearing them. The purpose of this research was to determine the impact mitigation properties of two commercially available women’s lacrosse headgears (the Cascade LX and the Hummingbird v2) across a variety of impact types and severities and to incorporate rotational velocity kinematic concussion metrics in impact analysis because of their correlation to brain strains. Because polymers that are commonly used in sports headgears have been shown to exhibit cold temperature hardening, the influence of cold temperatures on the ability of the headgears to mitigate impacts was also studied. Linear impactor and ball impact testing was performed on ambient and cold conditioned headgears. The kinematic concussion metrics peak linear acceleration (PLA), peak rotational acceleration (PRA), peak rotational velocity (PRV), head injury criterion (HIC15), and brain injury criterion (BrIC) were calculated for each impact. Results showed that both headgears were able to significantly reduce all five metrics, but that this reduction was much more subtle for the two rotational velocity metrics (PRV and BrIC). Cold conditioning did not have significant effects on the headgears’ ability to mitigate impacts. Materials that were used in the headgears were then tested in compression at various strain rates and at ambient and cold temperatures to acquire their mechanical characterizations. These characterizations can be used in future finite element analysis studies to more accurately investigate how the headgears are able to protect against concussions through brain strain analysis and to study how much they may endanger other players that are not wearing headgear.