Impact performance of ice hockey helmets: head acceleration versus focal force dispersion

Abstract

Modern sport helmets certified to various international safety standards have virtually eliminated the incidence of cranial fracture and fatal brain injury in contact sports; however, the occurrence of diffuse brain injuries (mTBI) are still prevalent. Local contact mechanics between the colliding surface (helmet/head) need to be considered as global measures of acceleration and are insensitive to load distribution measures which are indicative of helmet performance. The purpose of this study was to demonstrate the ability to capture localized load distribution response between the helmet and headform and to examine factors that may influence these measures. Twenty-five flexible force sensors were arranged in a 5 × 5 array about three impact sites (front, side, rear) of a 575 mm EN960 headform. Test factors included helmet model (5), impact location (3) and temperature (21 °C, −25 °C) as well as repeated impacts (3). Testing procedure followed the CSA Z262.1-09 standard at the defined locations. Average error calculated during sensor calibration was 2.8 ± 1% with an R² value of 0.987 ± 0.009. As expected, peak global force correlated well to peak acceleration (R² = 0.98) but weakly corresponded to peak focal force (R² = 0.22). Furthermore, both load distribution magnitudes and patterns were found to vary substantially with mixed effects between helmet models, impact locations, and temperatures. Given these findings, this novel approach may be used to quantify local contact mechanics between the colliding surface/helmet/head.