Could a Compliant Foam Anvil Characterize the Biofidelic Impact Response of Equestrian Helmets?

The research article investigates the performance of equestrian helmets against impacts from falls onto soft surfaces like turf. The study establishes a relationship between ground conditions and the response of a falling helmet, which is used to propose different types of synthetic foam to mimic turf in laboratory tests.

Objective

• The objective of the study was to provide a more accurate method of testing the effectiveness of equestrian helmets against impacts from falls on compliant surfaces such as turf. Until now, these kinds of tests have not been adequately studied, leaving a gap in the understanding of helmet efficiency under complex real-world conditions.

Methodology

• The researchers started by conducting field tests, dropping an instrumented hemispherical impactor from 1m and 2m heights onto a turf racetrack. These tests aimed to establish kinematic response characteristics and ground stiffness under different “going rating” conditions, which is a standard measure of racetrack conditions.
• Based on the data collected from field tests, three synthetic foam anvils, designed to simulate various ranges of “going rating,” or ground conditions, were proposed.
• The synthetic foams corresponding to Heavy-Soft (H-S), Good-Firm(G-F), and Firm-Hard(F-H) going ratings served as turf surrogates for lab tests.
• Subsequent laboratory experiments involved dropping a helmeted headform onto both natural turf and the turf surrogate anvils using a monorail drop rig.

Findings

• The “Hard” going rating in field tests resulted in higher peak linear accelerations and stiffness, and shorter impact durations compared to “Soft” and “Heavy” ratings. There were no significant differences among the other going ratings, but an overall relationship between going rating and kinematic response was evident.
• The laboratory experiments revealed similar linear and rotational accelerations when a helmet impacted natural turf, and its surrogates, to those found in concussive sports falls and collisions.
• This suggests that the proposal of using synthetic foam anvils as turf surrogates in helmet testing can provide a more accurate understanding of helmet efficiency in real-world conditions.

Implications

• The findings highlight the importance of considering the compliance of the ground surface during fall impact when designing accident reconstruction tests and helmet certification tests.
• Overall, the study helps to improve testing methodologies for equestrian helmets, which could eventually contribute to injury reduction in the sport.