Dr. Joel Stitzel, professor of biomedical engineering at the Wake Forest University School of Medicine, is a leading researcher in computationally modeling one of the most complex systems in the world: the human body. You’ll see one result of his collaboration with NASCAR this week at Watkins Glen.
Stitzel appears a typical academician with his neatly trimmed, just-starting-to-gray beard and wire-rimmed glasses. But his research protects athletes from Kyle Larson to kids in youth football leagues.
Stitzel is one of an increasing number of external researchers working with the NASCAR R&D Center to keep driver, crew members and fans safe.
Meeting of the minds
Dr. John Patalak, NASCAR’s vice president, safety engineering, first met Stitzel while both were working on a NASA project to develop a new landing vehicle. NASA was using NASCAR’s crash data to estimate head-injury risk for astronauts.
“That’s when I first realized that, not too far up the road, there was a Center for Injury Biomechanics,” Patalak said. “And in 2015, we got introduced to Dr. Stitzel directly and learned about the mouthpiece sensor.”
The holy grail for researchers like Stitzel and Patalak is developing a computer model that accurately predicts the detailed behavior of the human body under any impact.
That’s a tall order.
The human skeleton has 206 bones. Add to that around 78 organs, some squishy, some filled with gas and one (your skin) holding it all in place. There are also muscles, tendons, joints and more.
But you can’t create a computer model out of nothing. Developing a model is like climbing a spiral staircase. The first step is creating the model, The second is using the model to make predictions. Each successive pair of steps is checking your model’s prediction against real-world data and revising the model in response.
If experimental data aren’t accurate, the model won’t be accurate either. Sensors that measure velocity and acceleration have been placed in helmets and in ear canals; however, not all athletes wear helmets, and helmets can move relative to the head. The coupling between sensors and the ear canal isn’t always robust.
Stitzel and Patalak believe the most accurate data comes from coupling sensors directly to the skull. That’s where mouthpieces come into play. The upper jaw is part of the skull, so coupling to the upper teeth is an ideal way to measure head motion.
The mouthpiece sensor
The photo below shows the mouthpiece Stitzel and his collaborators developed to ensure they were testing their models against the best possible data.
It’s similar to the mouthguards those of us who clench or grind our teeth may wear. This one, however, comes with accelerometers and gyroscopes. And tiny batteries.
NASCAR drivers can opt in to wearing a mouthpiece during practices and/or races. Many choose to do so, reasoning that their data will help the sport.
“I’ve been wearing it, you know, the last year,” Ryan Blaney said. “I’ve always been very open, like ‘Hey, here’s my stuff … look at it and learn from it.’”
Each mouthpiece is custom made based on optical scans of the insides of each driver’s mouth. That ensures the devices fit correctly and are as non-intrusive as possible.
“If there’s any effect on speech, “Stitzel said, “It goes away pretty quickly. A lot of them (drivers) forget they’re wearing it, right? Then sometimes, if the driver wins a race and they’re wearing it, they’ve got to pull it out before an interview.”
Stitzel’s reputation was important to NASCAR choosing him to work with the drivers.
“There was a lot of trust placed in Dr. Stitzel,” Patalak said. “You’re asking them (the drivers) to do something during the most stressful portion of their week. But its largely now just part of the weekend.”
The relationship works both ways. Blaney experienced that firsthand after crashing in the Duels this year.
“They’ve done a good job of kind of explaining it to me,” Blaney said. “I mean, I’m not a data guy. They were with me the next day or two and kind of went over all the data. Here’s what you went though. This is what that means.”
Meet Watkins Glen’s new turtles
Most NASCAR fans who know about the mouthpieces became aware of them in April thanks to an exchange on X over modifications at Watkins Glen.
Connor Zilisch posted a photo showing two metal pieces (‘turtles’) installed inside the rumble strips of the bus stop’s inner loop. I’ve indicated them on his picture with green arrows.
In the screenshot from the broadcast of last year’s Watkins Glen race, you can see from the tire marks that most drivers try to driver as much of a straight line as possible between in the bus stop. That often results in all four tires bouncing over the rumble strips — or even leaving the ground.
The turtles — and a set of steeper black pyramids closer to the turn — prevent drivers from taking this shortcut. When Zilisch expressed disappointment, Larson stepped in to show why the change was needed.
The data Larson posted (below) show the mouthpiece recordings Stitzel’s group collected from his mouthpiece during the 2023 Watkins Glen race.
The left graph shows the linear (straight line) acceleration in units of Gs. The right graph shows rotational velocity. The scientific community is still learning how the two types of motions impact the brain differently.
Larson experienced an average linear acceleration of 11.7 g. To put that number in context, your head experiences a linear acceleration around 4 g when sneezing. Larson’s head was subjected to an average almost three times a sneeze each time he ran the inner loop during the two-hour race.
Some of the maximum linear accelerations reached 18 g. But, Stitzel points out, it’s important to note that the horizontal axis of each graph covers roughly 20 milliseconds.
“If I pull 18 Gs for 10 seconds, it’s going to hurt me, right?” Stitzel said, “But when it’s extremely short duration, like on the order of milliseconds, those events are not necessarily going to cause you a concussion. But I think what he (Larson) was trying to say with that post is that it does have the potential to bother you, right?”
Stitzel doesn’t recommend changes to tracks or safety equipment, but he is gratified to see his work already having an impact.
“NASCAR is a fantastic opportunity,” he said. “I haven’t been involved in many projects that have, I feel like, such an ability to effect change. Because they really care about what we’re measuring. I’m amazed by the pace of change: responding to input from drivers or from teams and trying to make adjustments and keep the sport competitive, but keep it safe.”
Motorsports safety researchers get more attention working in the highest echelons of the sport, but Stitzel also studies dirt racing. According to the National Institutes of Health, the prefrontal cortex — the part of your brain in charge of cognitive control among other things — doesn’t fully develop until age 25.
Many drivers start in dirt midgets and they start young. Dirt racers can experience more rollovers and harder vertical impacts. Protecting them is just as important as protecting drivers like Larson and Blaney.
One of those young drivers just might be a future Cup Series champion.