Most riding helmets might not be optimally designed for the kinds of falls horseback riders experience, a study has shown.
Standardized helmet tests measure the equipment’s reaction to hitting a steel anvil, but equestrians usually fall on softer, less rigid surfaces. They also tend to rotate their bodies and heads when they fall if the horse was in motion, which can result in very different kinds of forces compared to a straight drop onto an anvil, said Michael Gilchrist, PhD, Professor of Mechanical Engineering at University College Dublin, Ireland.
“This is not to say that current helmets are unsafe, but the idea is to understand whether they are adequately safe, or whether there is scope to make them even safer,” Gilchrist said.
Gilchrist and his fellow researchers equipped a standard adult human head form with accelerometers and fitted it with commercially available jockey helmets. They created three kinds of landing surfaces: the standard steel testing anvil, a turf surface made with dirt from an equestrian center, and a sand surface made from arena sand.
The scientists placed these surfaces under an automated dropping system with a monorail that released the helmeted head form from a hook at about the height of a rider’s head while mounted. They calculated both the forces and direction of impact as well as the estimated effects on the brain using a previously validated brain trauma model.
They found that impacts to the steel anvil resulted in much shorter impact durations compared to turf or sand, with significantly larger linear and rotational accelerations. That energy was transferred to the head, causing short-term high-magnitude accelerations, he said.
Straight drop impacts to the softer surfaces—sand and turf—caused less linear and rotational acceleration, but those impacts lasted longer, he said. That means the head and helmet were pushed against the surface for a greater period compared to the steel anvil. Longer impact times can contribute to concussions despite lower levels of peak acceleration and force.
In a Real Fall, the Head Usually Rotates
Gilchrist’s study only looked at straight drops onto the three surfaces, but in real-world conditions, riders’ heads would most likely get a lot more rotational movement during the fall if the horse is in motion, he said.
“One of the deficiencies in the current designs of (most) helmets is that they don’t appropriately take account of rotational acceleration,” said Gilchrist.
“You can imagine if a jockey falls from a horse, then the head will be subjected to both forward motion and vertical motion,” he explained. “So there will be a combination of linear deceleration and rotational deceleration at the time of impact against the ground. Rotational motion will effectively cause a different type of deformation in the brain tissue, and the energy-absorbing liner of the helmet, namely, shear, which is different from compression.
“So new testing standards and, consequently, new helmets should really be designed to account for both of those types of forces,” he said.
Current testing standards were designed to be easy to repeat in identical conditions throughout the world—hence, the idea of a “standard,” said Gilchrist. That’s more complicated when trying to add different and especially softer surfaces that could vary in consistency, making for a standardization challenge.
“The tests are designed as a best attempt to replicate real-world conditions,” Gilchrist said. “But our argument would be that there is scope to make them even more representative of the true kinematic conditions in the event of a fall. And that’s what our work is trying to do.”
The study did not look at equestrian helmets with the newer, patented Mips system, which is designed for multidirectional movement and used in snow and moto sports. “That is something we are planning to investigate in the next few months,” Gilchrist said. “However, the Mips technology is designed specifically to attenuate rotational acceleration, and, in principle, that should be more effective than conventional helmets.”
Clark JM, Connor TA, Post A, Hoshizaki TB, Gilchrist MD. The study, “The influence of impact surface on head kinematics and brain tissue response during impacts with equestrian helmets,” was published by the journal Sports Biomechanics.