Are Bike, Snow, and Equestrian helmets too stiff?

Despite passing rigorous certification tests, many helmets used in bike riding, snow sports, and equestrian activities may be fundamentally flawed in how they protect the brain. A growing body of research suggests these helmets are often too stiff, leading to a troubling trend: people walking away with head injuries even though their helmets show little to no visible damage.

Why is this happening?

At the heart of helmet safety is energy absorption. Most modern helmets rely on crushing a foam liner—usually expanded polystyrene (EPS)—to dissipate impact energy. Often times, these foams are tuned to crush at critical loads typical of the most severe impacts, typically at high speeds. This strategy works well for severe impacts against hard surfaces, such as those in helmet testing labs, where test headforms are slammed against rigid, steel anvils. But real-world accidents often involve softer surfaces (grass, sand, snow, or dirt) and can occur at a wide range of slow and fast speeds. In these scenarios, the helmet may not crush at all because the surface gives way before the helmet does, or the impact energy is not great enough to deform the foam substantially. The result? No foam damage means little to no energy absorption—so the brain takes the hit.

This issue was clearly illustrated in a study by Connor et al. (2019), who analyzed over 200 equestrian helmets involved in real-world accidents. They found that in nearly half of all reported head injury cases, the helmet showed no signs of damage—suggesting the foam never deformed to absorb the impact. Even more concerning, helmets certified to the most stringent standards (like Snell) were overrepresented in these undamaged-yet-injured cases, indicating that stiffer helmets might be exacerbating the problem in low-speed, soft-surface impacts by requiring more impact energy to begin crushing.

In a follow-up study, Connor et al. (2021) validated these observations with controlled lab tests. They confirmed that there are stark differences in energy absorption between rigid surfaces (like steel anvils)  and soft surfaces (like sand) during helmet impacts. They also showed that helmet foam often doesn’t deform at all in the common impact scenarios they reconstructed in the lab, leaving the brain vulnerable to injury. The team concluded that helmet performance is "clearly not optimised either for impact against soft surfaces or for relatively low velocity impacts".

This “overly-stiff” problem isn’t limited to horseback riding. Similar issues have been observed in bicycle and snow sports helmets, which also rely on EPS foam and are tested using rigid anvils under high-energy conditions. But everyday falls on bike paths, snowy slopes, or trail rides don’t always meet those extreme conditions. When the helmet doesn’t crush, it doesn’t help the wearer like it could.

What can be done? 

The research points to a need for better-aligned certification tests and softer, more responsive helmet liners that can activate at lower forces. An ideal solution for any helmet or headgear would involve adaptive impact attenuation that can protect you at high speeds and low speeds, grass or pavement, summer or winter. In short, a helmet that passes today's standards may not be perfectly tuned for wide breadth of dangers we are faced with in the real world. As the science on injury risk evolves, so too must the equipment meant to protect us.

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