We know head injuries aren’t rare in fire-rescue, and we’re likely still undercounting them.
In a five-year period from 2020–2024, the National Fire Protection Association found head injuries accounted for roughly 9% of injuries sustained on the fireground.1 Most of those were to eyes, ears, noses and mouths, but nearly half occurred to other areas. And a major literature roundup published in 2026, while noting that data were limited and inconsistent, found self-reported lifetime firefighter TBI prevalences ranging from 62%–77%.2
That points to a lot of impacts, but firefighter injury surveillance isn’t exactly set up to collect detailed information on head injuries or impact exposures. A firefighter who’s knocked down, strikes his head and feels dazed but doesn’t seek care, for instance, may not be captured. But the ways in which fire and EMS providers may suffer head trauma are numerous, including structural collapse, falling debris and other objects, slips/trips/falls and assaults.
Taking care of those providers’ valuable noggins is a primary focus for Team Wendy, a provider of protective headgear for first responders, the military and others. In 2024, the organization unveiled a novel test apparatus designed to produce critical information about the forces accompanying various types of head impacts. Today that’s bearing scientific fruit.
“We want to get all this data out there and peer-reviewed and published,” said Ron Szalkowski, Team Wendy’s head of research and development. “We want to use this to advance the state of understanding for everyone and, at the same time, make better decisions in how we design products.”
Turning science into solutions
DREW — an acronym for Dummy for Rotational Evaluation of Wearables — is a helmet-testing system that can simulate both the linear and rotational motion involved in falls and other head impacts. It uses a 50th-percentile Hybrid III head, neck and torso mounted on a pivoting assembly that allows Team Wendy experts to recreate both direct strikes and whiplash-type events from all angles and directions.
Standard in automotive crash testing, Hybrid III dummies use a neck designed to approximate human flexion and extension response with movement of the head. This allows measurement of realistic angular velocities with neck rotations. Rotational motion is the mechanism most associated with diffuse brain and axonal injury, and it’s essentially invisible to the simple headform drop tests historically used in certification standards.
“We are definitely not the first ones to look at the importance of rotation — there’s been a lot of research on it,” said Szalkowski. “However, we have done some unique things with the DREW test rig where we’ve kind of pulled together what we think are the best of many different test capabilities. Part of that was with our academic collaborators guiding and telling us what we need to see in a test, and part of that was also getting real-world data.”
Key among those academic collaborators has been Christian Franck, Ph.D., a professor of mechanical engineering and acting director of the Center for Traumatic Brain Injury at the University of Wisconsin-Madison. Franck leads a project funded by the U.S. Office of Naval Research (ONR) called PANTHER, for “Physics-based Neutralization of Threats to Human Tissues and Organs,” the goal of which is to reduce TBI by helping turn scientific discovery into protective solutions.
It’s a multifaceted national project with numerous partners, one of which is Team Wendy. “The goal is to develop a real kind of biological, physics-based understanding of how the body and brain operate to basically inform improved protection to reduce injury in the field,” said Szalkowski. DREW is a key component.
How the brain gets hurt
While the brain is hard to compress, it is highly susceptible to shear — it won’t change volume but changes shape easily. Work by Franck, Robert Morris University’s Rika Wright Carlsen, Ph.D., Brown University’s Haneesh Kesari, Ph.D., and others has established that what damages axons is that shape change — strain, the local stretching of brain tissue. Head acceleration is a proxy for gauging it.
Strain is overwhelmingly a rotational phenomenon. When the head turns rapidly, the skull rotates before the brain does. The brain’s outer surface drags the inner brain behind it, creating a shear wave. Brain tissue is soft, so that wave travels slowly, and peak strain arrives after impact.
The rate at which this occurs matters as much as magnitude. Brain tissue and axons (the long nerve-cell projections that conduct impulses away from the cell body) are viscoelastic: Pulled slowly, they flow and accommodate, like Silly Putty; torn quickly, they are stiffer and easily damaged. A stretching force applied over 10 milliseconds will thus be more damaging than one that lasts a full second. That’s why literature often considers strain rate alongside force in brain injury, and modeling work by Carlsen and Franck has shown angular acceleration and angular velocity affect peak strain and strain rate, while angular jerk can have a stronger effect on peak strain rate.3
No single scalar captures that, which is why DREW adds a neck and torso to the headform: Instead of one peak number from one drop, it produces a time history of how a real head actually moves.
“When we first met with Christian, he was doing this cellular work at Brown University, and we realized this was the kind of thing we needed to understand in order to make a better helmet,” said Szalkowski. “He was interested to see if his research could actually lead to real, improved equipment that better protected people. So we put together a paper and brought in a couple more collaborators and shopped the idea around, and we got enough interest with ONR that they funded that initial research.”
Real-world data refines the model
To supplement that lab data, Team Wendy also brought some real-world data to the table. This came from hard parachute landings experienced by paratroopers at the U.S. Army Airborne School wearing instrumented mouthguards.
“That’s not exactly like a rescue effort, but it’s a real-world event where someone’s coming in with some velocity and hits the ground,” Szalkowski noted, “and it’s repeatable enough that we could get some data to see what’s occurring with the head.”
Instrumented mouthguards are a useful field sensor for head kinematics because they clamp to the upper teeth and don’t move much. Team Wendy used the data to calibrate DREW for greater accuracy, adjusting its drop angle and whiplash distance until its output was within 4% of the measured paratrooper data.
This unique approach — tuning lab conditions to reproduce real measured events — provided the missing link identified by Carlsen and Franck: If no single kinematic number predicts tissue strain, then a test rig can’t be validated by hitting one target value — it has to reproduce the whole pulse, which requires field measurements of what real pulses look like.
“One of the key things here is that we’re seeing an angular velocity — the head is moving in a rotation prior to making contact and having a big deceleration,” said Szalkowski. “A lot of the prior types of tests miss this pre-impact angular motion that we were able to get dialed in and reproduce.”
A surprising liner finding
DREW has already produced important findings, and Team Wendy representatives presented some last fall at the Personal Armour Systems Symposium (PASS) 2025 in Belgium.
In addition to outlining their parachute-impact calibrations, their investigators compared the performance of the company’s EXFIL ballistic helmet liner to that of a more rigid high-density foam ballistic liner. The high-density liner produced higher peak linear and angular acceleration and did not meaningfully reduce peak angular velocity. “In short,” the company concluded, “more rigidity or density doesn’t always mean better protection in real-world falls.”
“We want to get all this data out there and peer-reviewed and published. We want to use this to advance the state of understanding for everyone and, at the same time, make better decisions in how we design products.”
“That was a surprising finding,” Szalkowski said. “If you were just running a linear test, you’d think the optimal foam was a pretty high-stiffness foam. But when you put those materials into DREW, it didn’t show that. In a lot of cases, it was actually worse than a relatively softer pad.”
One of several EXFIL models available, the EXFIL SL ballistic helmet features an Air FIT liner system made with proprietary Zorbium foam technology developed through extensive TBI-prevention research. It supplements this with an ultra-high molecular weight polyethylene shell. The newer RECON Tactical puts an Air FIT liner in a bump helmet developed for tactical law enforcement, search and rescue and other demanding missions.
DREW continues to inform new work. The company has now performed more than 1,000 test impacts with it, including evaluations of the RECON. They’ve also provided data back to collaborators like Carlsen, who can then model the resulting patterns of brain-tissue strain.
Other work has looked at sensors. “We’re interested in what kind of sensors could you mount to a helmet to get accurate head impact readings,” Szalkowski said. “If we can get more real-world data, we can design the helmets to real-world experiences. And then long-term, maybe we can get data that might help you at an individual level, maybe even predict injury for someone wearing a helmet. ‘You know, that was quite a bad impact — you should get checked out.’”
Changing how we think about the head
Standards don’t change quickly, and generally not until consensus wisdom precedes them. DREW is helping Team Wendy change the consensus around how head injuries in the fire service are understood, measured and protected against.
While the PASS data concerned military helmets and testing has focused on ballistic and bump helmets, DREW’s findings should ultimately also benefit structural firefighting helmets and all kinds of responder head protection.
“What we’re seeing now is companies going out and developing technologies that can perform on DREW, even though DREW isn’t standardized or required anywhere yet,” said Szalkowski. “But we’ve presented it to standards groups like ASTM, so I think it’s advancing. And then it’s advancing it in the eyes of the consumer as well, with all these aspects to consider beyond the basic certifications that are required.”
For more information, visit Team Wendy.
References
- “Municipal firefighter injuries on the fireground.” Richard Campbell. National Fire Protection Association. December 31, 2025. www.nfpa.org/education-and-research/research/nfpa-research/fire-statistical-reports/municipal-firefighter-injuries-on-the-fireground
- “Systematic review and meta-analysis of traumatic brain injury in first responders.” Katherine J. Hunzinger, Kayla Riel, Carly Smith, et al. Journal of Head Trauma Rehabilitation. July 14, 2026. https://pubmed.ncbi.nlm.nih.gov/42461657/
- “A quantitative relationship between rotational head kinematics and brain tissue strain from a 2-D parametric finite element analysis.” Rika Wright Carlsen, Alice Lux Fawzi, Yang Wan, et al. Brain Multiphysics. 2021. www.sciencedirect.com/science/article/pii/S2666522021000046
