The influence of impact surface on head kinematics and brain tissue response during impacts with equestrian helmets.

This research investigates how different surfaces affect the impact to a horse rider’s head when wearing equestrian helmets. It reveals that helmet testing focuses too much on hard surface impacts, like steel, whereas, in reality, falls tend to occur on softer surfaces, such as turf and sand.

Introduction and Purpose

• The basis of the study was to scrutinize the disparity between current helmet certification tests and real-life scenarios in equestrian sports. Presently, equestrian helmet checks focus on impacts against a steel anvil, but in actual cases, falls typically happen on softer grounds like turf or sand.
• By examining how different surfaces affect head impacts, this study aims to discern potential improvements in helmet design and testing. Therefore, the research focuses on comparing head kinematics (motion characteristics) and brain tissue responses to impacts on three surfaces: steel, turf, and sand.

Methodology

• To test the varied impacts, a Hybrid III headform with a helmet was freely dropped onto the three surfaces at three different impact points.
• The researchers measured peak linear acceleration, rotational acceleration, and impact duration of the headform, attempting to gauge how much impact the head endured during the simulated fall.
• The recorded acceleration values were then fed into a three-dimensional finite element head model, which estimated the Maximum principal strain (MPS) and von Mises stress (VMS) in the cerebrum (the largest part of the brain). MPS and VMS values are used to evaluate the structural integrity and deformation of the brain tissue after impact.

Findings

• The research highlighted that impacts to a steel surface strongly escalated peak head kinematics and brain tissue responses, approximately two to three times higher than impacts against turf and sand.
• Interestingly, the duration of the impact with the steel anvil was less than half of that with turf and sand, indicating that hard surfaces might cause rapid, strong effects.
• Despite softer surfaces causing less immediate damage than steel, the response magnitude for impacts to turf and sand were still within the concussion range reported in relevant literature, raising concerns about current helmet safety capabilities.

Conclusion

• From this study, it can be inferred that equestrian helmet design and certification tests should cater to impacts with varied surfaces. The results emphasize the need not just to consider steel (or similar hard surfaces) but also softer, more compliant surfaces when designing and testing helmets.
• The research underscores that while softer surfaces may seem less dangerous, they still pose significant risks for concussion. Therefore, efforts should be made to enhance the helmet’s ability to protect from impacts on these surfaces too.