Football helmet fitment and its effect on helmet performance

摘要

A method and system to objectively quantify helmet fitment was designed and developed. It measures the pressure between the energy-absorbing material in the helmet and the athleteu27s head. This system is also capable of measuring surface pressure during impact events. A volunteer-based field study was conducted to quantify how helmets were fitting athletes in a real-life setting. The helmets fit athletes in varying degrees of tightness and evenness. Most athletes (59%) had the highest pressures in the frontal area and 29% had the highest pressure in the occipital area. A large-sized helmet on the Hybrid III headform represented how most helmets fit the athletes in the field.Impact testing was also conducted to assess the effects of helmet fitment. Four impact locations were selected (F, UT, C and D). Two fit variations were analyzed: loose vs. tight (and more uniform). Overall, the tight-fitting condition resulted in higher linear acceleration-related response parameters (HIC - p=0.26), (GSI - p=.088), (apeak - p=0.097); however, there were significantly lower angular accelerations (p=0.003) and lower angular velocity (p=0.081). Results were significant (95% C.I.) for 3 of the 4 impact locations. Generally, a tighter and more evenly fitting helmet resulted in more of a linear response of the headform and less angular acceleration. The tighter (and more uniform) fitting helmet resulted in the surface pressure being distributed over a larger area.The helmet used for the impact testing was equipped with the Head Impact Telemetry (HIT) System. The reported response parameters from the HIT System were compared to the Hybrid III headform data. The headform data was considered to be the accurate measurement. No correlation could be found between the HIT System data versus the Hybrid III headform data. Relative error of the HIT System was significantly different than the headform data for HIC (p =0.001), GSI (p u3c0.001), Peak Linear Acceleration (p =0.013) and Peak Angular Acceleration (p u3c0.001). Absolute error and relative error of the HIT System was also calculated for each of the response parameters.