How do extreme G-forces affect Olympic bobsledders?

Olympic sliding sports – bobsled, luge and skeleton – are known for their speed. Athletes chase medals down a track of ice at up to 80 or 90 mph. With this thrill comes the risk of “sled head.” Athletes use the term to explain the dizziness, nausea, exhaustion and even blackouts that can follow a brain-rattling run. Untreated, this can turn into concussions and subconcussions. But there’s still a lot more to learn about this condition. So today, host Emily Kwong https://www.npr.org/people/767284140/emily-kwong speaks with two experts about the medical research into sled head – and how the sport would need to change to protect athletes’ brain health. Check out more of NPR’s Olympics coverage https://www.npr.org/series/g-s1-104526/2026-olympics. Interested in more Olympic science? Email us your question at [email protected] mailto:[email protected]. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:00Speaker 00

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• 0:18Emily Kwong?

  You're listening to Short Wave from NPR.

• 0:25Emily Kwong?

  This Friday, the Olympic cauldron will be lit, signaling the start of the Winter Games in Italy. We will see figure skating, ice hockey, and of course, the sliding sports. Bobsled, luge, and its sister sport, skeleton, where you slide down the ice track headfirst, going up to 80, sometimes 90, miles per hour.

• 0:44Speaker 02

  To me, it felt like the closest thing you could get to flying. It was like a roller coaster that you could control. But then, on the bad days, it felt like a minute of a car crash.

• 0:54Emily Kwong?

  Aaliyah Snyder was a competitive skeleton athlete. The sport gave her a huge adrenaline rush. But there was something else, too. Some runs left her feeling shaky afterwards, disoriented.

• 1:05Speaker 02

  Then it became more clear, over the course of the day, that I would have trouble concentrating. I would be feeling more nauseous. I would just kind of feel more irritable, have trouble with lights, things like that.

• 1:21Emily Kwong?

  And she was told back then, don't worry, it's normal.

• 1:25Speaker 02

  Oh, you know, everybody's kind of a little bit concussed all the time.

• 1:28Emily Kwong?

  But nowadays, there is a term for the symptoms that can follow a really shaky or high G-force run. And that term is sled head. The dizziness, nausea, exhaustion, and cognitive problems that eventually damaged Aaliyah's brain and body.

• 1:44Speaker 02

  My head didn't tolerate the vibrational forces. And I just kept training through a lot of symptoms that I kept accumulating the more time I spent on the track. I probably ended with around six concussions that I was really not able to compete at all. Like, I had to be medically retired. I was advised to stop because I was just not recovering from smaller and smaller hits on the track.

• 2:10Emily Kwong?

  And she was far from alone. Throughout the history of the sliding sports, many bobsled and skeleton athletes have struggled with sled head. But a lack of research meant the medical community didn't have good answers on how Aaliyah could treat her symptoms.

• 2:23Speaker 02

  So that's where I decided to go into neuropsychology and focus my career on those types of questions.

• 2:30Emily Kwong?

  Now a neuropsychologist at the University of Florida and UCLA, Aaliyah is among a handful of scientists who want to get to the bottom of what is going on with sliding athletes and their brains. Sled head is something athletes talk about, but researchers found they're not always telling their coaches about it.

• 2:46Speaker 03

  They wouldn't tell the coaching team or the medical team for fear of being excluded from the next training day and potentially overlooked for the team. That was a disincentive to that player to tell anybody it was happening.

• 3:04Emily Kwong?

  Peter McCarthy is a neurophysiologist at the University of South Wales and the Durban Institute of Technology. And he says to truly protect athletes' brains, it may be the sport that needs to change.

• 3:18Emily Kwong?

  So today on the show, shining a light on sled head, how the impact of bobsled and skeleton on athletes' brain health has been under researched for years, and what science is needed to make the sport safer for all. I'm Emily Kwong, and you're listening to Short Wave, the science podcast from NPR.

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• 5:11Emily Kwong?

  Okay, just for a second here, I want to talk about G-forces. Sliding athletes are experiencing really high G-forces when they go around those turns, especially at the elite level like in the Olympics. Gravitational force attracts objects to other objects. For us walking around on Earth, the acceleration due to gravity is 1G. But say you're in a car going around a curve. People in the car feel their velocity changing, acceleration. And that feels like an intense force, more intense than the pull of Earth's gravity keeping you stuck to Earth. And it is, it's more than 1G. Roller coasters can give you over 5Gs. And bobsledding can go just as high on those turns. In skeleton, the intense G-forces and positioning can cause the athlete's head to hit the ice.

• 5:56Emily Kwong?

  And Peter McCarthy says all of this can be really rough on the body.

• 6:00Speaker 03

  The consequence of that in that you've got soft brain tissue hitting and accelerating skull. So the brain basically squidges up against the skull.

• 6:12Emily Kwong?

  And remember, as Aaliyah Snyder says, "The brain is the central command system of the body."

• 6:16Speaker 02

  Yeah, the brain is tethered as well in the brainstem. So it's not just the impact to the skull, but there is the stretching forces. Like you have a set point as the brain goes into the spine and the rotation from that as well.

• 6:33Emily Kwong?

  And in those moments when athletes are experiencing those G-forces, helmets can protect against some damage, but they can't protect the brain moving within the skull. That can cause a concussion or subconcussive impacts. And to study the vibration that athletes are experiencing on the sled, Peter built a special sensor for their helmets. He told us how it works and why it matters.

• 6:57Speaker 03

  Yeah, we put little sort of three axes devices inside the helmet on the back of the person and so on. And that's how we were able to tell when the head was going in one direction and the body was going in another. But we, basically, you pick up a range of frequencies. There's some quite low ones, but majority are below 50 hertz, 50 shakes a second, in a sense. And the problem with it is that the lower frequencies allow more movement to transmit through to the system.

• 7:31Emily Kwong?

  What are you planning to do with the data?

• 7:33Speaker 03

  We reported the findings to the International Bobsleigh Skeleton Medical Committee.

• 7:39Emily Kwong?

  Right, and they're part of the international group that administers the sport, the International Bobsleigh and Skeleton Federation?

• 7:45Speaker 03

  Yeah, because I wanted to alert people to the potential risk to the athletes. But again, it's unquantified. At the moment, this is not fully known.

• 7:56Emily Kwong?

  There isn't a ton of published research, but you both have been a part of an effort to create that body of work. And Aaliyah, you work in a clinic now as part of the UF Health Interdisciplinary TBI Program. And you work with sliding athletes who have injuries. They are sent to your clinic for evaluation, for treatment. What have you seen sled head do to the brains and bodies of your patients over time?

• 8:23Speaker 02

  There's a wide range of how sled head can look. And, you know, I think sled head is a useful term for discussing kind of the phenomenon broadly, less useful individually. Because what our athletes are experiencing is kind of a combination of the specific type of sport that they're in, whether it's bobsled or skeleton. But also what their position is, what their medical history is. But what we're seeing is that for some athletes, after, I'll speak for some bobsled athletes, after they have one pretty Pretty good concussion or TBI from, you know, a particularly bad crash.

• 9:02Emily Kwong?

  Traumatic brain injury, TBI.

• 9:04Speaker 02

  Yes, a traumatic brain injury. That there seemed to be showing some reduced tolerance to those stress forces on the track.

• 9:14Speaker 02

  And one of the things that my research and our clinical experience, we're interested in is the role of the autonomic nervous system. What that is, is the kind of automatic regulation, the subtle changes that your body and brain are doing all the time. Your brain is the central control unit for that. So that could be, you know, those really small changes in pupil size in response to light. It can be changes in your heart rate as you breathe. You know, breathing patterns, all of that are making microscopic level changes and macroscopic level changes at all time. And that carefully choreographed relationship between your nervous system branches

• 9:54Speaker 02

  has heavily involved in cognition, emotional regulation, and physical symptoms. And so what we're seeing for some of these bobsled athletes is that they'll have a big injury and then they will start to tolerate the large, high G-force curves less well. So start to either feel like they're losing consciousness in a couple cases. Kind of more, more susceptible to these broad, nonspecific headache, fatigue, irritability, attentional difficulties afterwards.

• 10:30Emily Kwong?

  You're saying this is more of like a subtle disconnect in your body's responses over time?

• 10:34Speaker 02

  Mm hmm. Kind of, yeah, aware and terror on the accuracy and, and kind of tolerability of the nervous system to stressors. And I use stressors, not just cognitive or emotional stressors, but any type of thing that your body is having to adjust to, which is can even be like standing up.

• 10:52Speaker 03

  And there's other factors as well. One of the people I've looked at in the past that had a concussion. And when the eyes were closed on this individual, there was a noticeable head shake, like they were trying

• 11:07Speaker 03

  Trying to find something. It was an uncontrollable one, which was exacerbated, made much worse by doing some runs. And this is why there needs to be a recognition within the system. Because if you're treating a person who wants to go back as an athlete and recover, they need to be given sufficient time to actually recover.

• 11:29Emily Kwong?

  Yeah. What it sounds like medically is happening is the subconcussive injury, like that initial insult to the body is a problem. It's not great. But the deeper problem is that the athlete is not then taken off the track and allowed to recover. And that leads to like this cascade of effects. Is that right? Or is that what you theorize?

• 11:55Speaker 02

  You know, I think one of the issues is that we talk about concussion as all or nothing. We're trying to extend the discussion to subconcussive. But that also comes to this idea of what do we do afterwards? And part of recognition is also the idea that it can be better, that this is not necessarily a retirement or everything, everything's fine, or you have to retire kind of decision. The brain is always changing in positive and negative ways. We can leverage that. We can do cognitive training. We can do physiological training. We can do autonomic re-regulation training.

• 12:35Speaker 02

  But it doesn't abide by the rules that we typically think of, the push-through-it mindset. So there's not just like one medication we can do or develop. We have to think of it as a living organism that is biological, but also responds to a lot of other types of inputs, cognitive, emotional, physiological, behavioral. We need to take all of that into consideration when we're rehabilitating someone, and it is possible.

• 13:04Emily Kwong?

  It sounds like there is hope, you're saying, for these athletes and things can be done. Peter, what do you wish the International Bobsleigh and Skeleton Federation would do? You've spoken to that body, to their medical committee.

• 13:18Speaker 03

  Well, I think the key with it is this. I'm a great believer that athletes want to compete, and they will suffer to compete. Everybody who's ever played a sport. Will quite happily play that sport injured if it means they've got a chance to win. And I think the problem there is you cannot rely on anybody to do it, to actually observe and say, timeout, come here. You need to have an objective measurement. And that's why I feel there needs to be some recognition, sensors, something in place to actually record what's going on.

• 14:01Speaker 03

  If you were to wear an exposure meter and say, you've had sufficient for this week, go and have a rest, you can get higher performance. You can do all of these things. But it's recognizing and putting a structure in place to actually protect the athlete.

• 14:17Emily Kwong?

  That is Aliyah Snyder and Pierre McCarthy. Thank you both so, so much for sharing this enormous amount of information, what we know and what we don't, and really centering the athlete's well-being.

• 14:30Speaker 02

  Thanks so much, Emily. It was a pleasure.

• 14:32Speaker 03

  Yeah, thank you, Emily.

• 14:33Emily Kwong?

  And a final note here, we reached out multiple times to the International Bobsleigh and Skeleton Federation, USA Bobsled Skeleton, the British Bobsleigh and Skeleton Association, and Bobsleigh Canada Skeleton for comment on how they're trying to address sled head. And they didn't get back to us before publishing. If you liked this episode, follow us on the NPR app or wherever else you get your podcasts. That way, you never miss another one. This episode was produced by Rachel Carlson and edited by our showrunner, Rebecca Ramirez. Tyler Jones checked the facts. Jimmy Keely was the audio engineer. I'm Emily Kwong. Thank you for listening to Short Wave from NPR. See you next time.