Drop Test Kinematics Using Varied Impact Surfaces and Head/Neck Configurations for Rugby Headgear Testing

Abstract

World Rugby employs a specific drop test method to evaluate headgear performance, but almost all researchers use a different variation of this method. The aim of this study was, therefore, to quantify the differences between variations of the drop testing method using a Hybrid III headform and neck in the following impact setups: (1) headform only, with a flat steel impact surface, approximating the World Rugby method, (2 and 3) headform with and without a neck, respectively, onto a flat MEP pad impact surface, and (4) headform and neck, dropped onto an angled MEP pad impact surface. Each variation was subject to drop heights of 75–600 mm across three orientations (forehead, side, and rear boss). Comparisons were limited to the linear and rotational acceleration and rotational velocity for simplicity. Substantial differences in kinematic profile shape manifested between all drop test variations. Peak accelerations varied highly between variations, but the peak rotational velocities did not. Drop test variation also significantly changed the ratios of the peak kinematics to each other. This information can be compared to kinematic data from field head impacts and could inform more realistic impact testing methods for assessing headgear.

The Impact of Drop Test Conditions on Brain Strain Location and Severity: A Novel Approach Using a Deep Learning Model

“…This result conforms with previous work that has investigated how neck inclusion impacts the kinematics of the headform. Sitt et al [ 58 ] have shown that inclusion of the neck during drop testing did not significantly influence the peak linear and rotational accelerations, or the peak rotational velocity for both height- and energy-matched impacts. It did, however, significantly influence the shape of the rotational velocity kinematic trace and, by extension, the rotational acceleration trace.…”

“…All impacts were carried out on a twin wire guided drop test rig using a HIII headform (50th percentile male model) instrumented with a nine accelerometer package (NAP) [59]. Three variations of the drop test method were carried out for comparison based on previous work by Stitt et al and Draper et al The first used a HIII head and a standard 1-inch Modular Elastomer Pad (MEP) for the impact surface (manufactured by Cadex Inc.), with no neck involved [58,60]. The second and third drop test variations used were taken from the same authors' study of rugby headgear [61].…”

“…These results show that impact energy alone does not directly determine the resulting regional peak and mean MPS, thus indicating a more complex interaction between variables. This highlights that factors such as impact location and impact compliance (the overall stiffness of an impact) play a critical role in the resulting head kinematics [39,58,61] and thus brain injury. Interestingly, the trends between impact location and resulting strain were not always consistent between the 150 mm and 450 mm drop heights used in this study.…”

“…Previous work investigating the effect of drop test condition on the shape of the kinematic profiles of a Hybrid III (HIII) headform found rotational velocity to be largely unaffected [ 58 ]. This study aimed to deepen this analysis by investigating the relationship between drop test condition on the location and severity of MPS within the brain.…”

Potential of soft-shelled rugby headgear to lower regional brain strain metrics during standard drop tests

“…Drop test kinematic data was taken from previous work by Stitt et al and Draper et al comparing the potential of rugby headgear to reduce linear and rotational accelerations. These drop tests were carried out on a 1-inch modular elastomer pad (MEP) angled at 0 and 45 • relative to the test rig base 15,45 . All impacts were carried out across four impact locations: forehead, front boss, side, and rear boss (labelled rear-rear boss), as shown in Figure 1 and 2.…”