Comparison of shell-facemask responses in American football helmets during NOCSAE drop tests

Abstract

This study compares drop tower tests of four commonly used football helmets, under the National Operating Committee on Standards for Athletic Equipment (NOCSAE) football helmet standard, to show that the tests need modification to include the facemask. In our study, the need for a more robust systematic approach to football helmet testing procedures is emphasized by comparing the Head Injury Criterion (HIC), the Gadd Severity Index (SI), and peak acceleration values for different helmets at different locations on the helmet under modified NOCSAE standard drop tower tests. Drop tests were performed on four modern football helmets at eight impact locations (front, front boss, side, rear, rear boss, top, front top, and front top boss), two different impact velocities (5.46 and 4.88 m/s), and two helmet configurations (“with facemasks” and “without facemasks”). Statistically significant differences (p < 0.05) were found in 41% of the comparisons between “with facemasks” and “without facemasks”. Addition of the facemask resulted in an increased HIC, SI, and peak acceleration response measures in 62% of these cases. For example, the stiffening boundary conditions arising from the attached facemask can decrease the helmet performance by up to 50% depending on the impact location when considering the peak acceleration (p < 0.001) as a metric. In terms of location, the top and front top impacts gave the largest HIC, SI, and peak acceleration values. In summary, these comparative drop test results revealed that the current NOCSAE test methods need improvement by attaching the facemasks to helmets and by including two new helmet impact locations (front top and front top boss). The modified NOCSAE football helmet standard test gives a more accurate representation of a helmet’s performance and its ability to mitigate on-field impact.