How do extreme G-forces affect Olympic bobsledders?

Summary

Short Wave - Episode Summary

Episode Title: How do extreme G-forces affect Olympic bobsledders?
Date: February 4, 2026
Host: Emily Kwong (NPR)
Guests:

• Dr. Aaliyah Snider (Former skeleton athlete, Neuropsychologist, University of Florida/UCLA)
• Dr. Peter McCarthy (Neurophysiologist, University of South Wales/Durban Institute of Technology)

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Main Theme & Purpose

This episode explores the under-researched brain health risks facing Olympic bobsled and skeleton athletes—specifically the phenomena of "sled head," a cluster of cognitive, physical, and emotional symptoms caused by repeated exposure to high G-forces and vibrational impacts on the track. Host Emily Kwong guides a discussion with former elite athlete-turned-neuropsychologist Aaliyah Snider and neurophysiologist Peter McCarthy about the science behind these injuries, real-world impacts on competitors, and the emerging ideas for making sliding sports safer.

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Key Discussion Points and Insights

1. The Athlete Experience: Euphoria and Danger

• Opening descriptions of bobsled, skeleton, and luge's intensity set the scene for the physical forces athletes endure (00:21–00:47).

• Aaliyah Snider details the initial thrill and latent danger:

  "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." (00:47–00:57)

• She recounts disturbing symptoms post-run—shakiness, disorientation, trouble concentrating, nausea, light sensitivity, and irritability that worsened as symptoms accumulated (00:57–01:24).

• Athletes were often told these issues were "normal" and rarely discussed them openly, fearing exclusion from competition (01:28, 02:49).

2. Sled Head: Recognizing a Hidden Issue

• Sled head encompasses dizziness, nausea, cognitive issues, and chronic brain injury—what was once an open secret or dismissed as “normal” wear and tear (01:31–01:47).
• Aaliyah Snider:

  "Oh, you know, everybody's kind of a little bit concussed all the time." (01:28–01:31)

• Lack of research and understanding made it hard for athletes or clinicians to treat or prevent these injuries; eventually, Snider suffered repeated, accumulative concussions:

  "I probably ended with around six concussions... I had to be medically retired." (01:47–02:13)

3. Why These Sports Are So Physically Extreme

• Explanation of G forces:
  • 1G = what we feel standing on Earth; bobsled/skeleton Olympic events can hit over 5Gs, comparable to roller coasters (05:03–05:59).
  • On tight curves and at high speeds, athletes’ brain tissue is forced against the skull, sometimes causing microtraumas or full concussions (05:59–06:32).
  • Helmets help, but can’t stop the brain from moving inside the skull (06:32).

4. Science Catches Up: Measuring the Risks

• Peter McCarthy discusses helmet sensors to measure vibration and acceleration, revealing just how much athletes’ heads and bodies are jerked—in some cases, the head and body move in different directions (06:56–07:30).

  "We put three axis devices inside the helmet...to tell when the head was going in one direction and the body in another." (06:56–07:10)

• Data has been presented to the International Bobsleigh and Skeleton Medical Committee, but much remains "unquantified" and under-researched (07:32–07:55).

5. The Nuanced Impacts of Sled Head

• Snider observes a spectrum of symptoms, from subtle cognitive decline to overt concussion. "Sled head" can look different from athlete to athlete, influenced by discipline, position, history, etc. (08:20–09:00).
• First traumatic brain injury or concussion may lower tolerance for subsequent brain stress; subsequent runs cause increasing sensitivity and impaired regulation of heart rate, breathing, and attention (09:02–10:28).
• The problem is cumulative:

  "Wear and tear on the accuracy and tolerability of the nervous system to stressors." (10:33–10:50)

6. Recovery Obstacles and the Push-Through Mentality

• Athletes seldom report symptoms for fear of losing their spot, and the prevailing “push through” culture discourages recovery (02:49–03:07, 11:28–12:57).

• Peter McCarthy:

  "Athletes want to compete and they will suffer to compete...so you cannot rely on anybody to do it [self-report]." (13:16–13:41)

• Need for objective monitoring; use sensors/"exposure meters" to determine when athletes should have a mandatory break (13:43–14:17).

• Aaliyah Snider:

  "The brain is always changing... We can leverage that. We can do cognitive training, we can do physiological training, we can do autonomic re-regulation training...we need to take all of that into consideration when we're rehabilitating someone. And it is possible." (11:53–13:03)

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Notable Quotes & Memorable Moments

• On the emotional toll:

  "You have to think of it as a living organism that is biological, but also responds to...cognitive, emotional, physiological, behavioral [inputs]."
  (Aaliyah Snider, 12:35–12:49)

• On systemic responsibility:

  "You need to have an objective measurement...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...but it's recognizing and putting a structure in place to actually protect the athlete."
  (Peter McCarthy, 13:43–14:17)

• A hidden, shared experience:

  "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."
  (Peter McCarthy, 02:49–03:07)

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Important Timestamps

• 00:47 – Aaliyah Snider describes skeleton, euphoria vs. fear
• 01:08–01:28 – Snider’s symptoms post-runs; normalization of “concussed all the time”
• 02:26–02:33 – Snider decides to study neuropsychology because of her experience
• 03:07 – McCarthy on why athletes hide symptoms
• 05:03–05:59 – Explanation of G forces; comparison to roller coasters
• 06:56 – McCarthy on helmet sensor research
• 08:20 – Snider describes clinical diversity of “sledhead” symptoms
• 09:02–10:28 – Discussion of the body’s regulatory system and cumulative injuries
• 13:16 – McCarthy on why sports governing bodies need objective measurement
• 13:43–14:17 – Recommendations for athlete exposure monitoring

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Conclusion & Calls for Change

• Science is still catching up with the lived experiences of bobsled and skeleton athletes, but clinical and technology advances are opening up possibilities for less damaging competition and more effective recovery.
• Both Snider and McCarthy advocate for systems—and a culture—that recognize physiological limits with objective measures (such as exposure meters), greater transparency, and nuanced, proactive medical support.
• The International Bobsleigh and Skeleton Federation did not respond to NPR’s inquiries at the time of the episode.

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Overall Tone

Conversational and empathetic, with a combination of scientific rigor, personal storytelling, and calls for systemic athlete protection—balancing scientific curiosity with athlete welfare.

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This summary covers all key content sections while skipping advertisements and promotional material, providing an engaging and practical overview for listeners and non-listeners alike.

Transcript

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[C]

You're listening to Short Wave from npr. 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.

[D]

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.

[C]

Aaliyah Snider 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.

[D]

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, you know, irritable, have trouble with lights, things like that.

[C]

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

[D]

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

[C]

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.

[D]

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.

[C]

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.

[D]

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

[C]

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. Sledhead is something athletes talk about, but researchers found they're not always telling their coaches about it.

[E]

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.

[C]

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. 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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[C]

Okay, just for a second here, I want to talk about g forces. Sliding. Athletes are experiencing high G forces when they go around those turns, especially at the elite level like in the Olympics. So gravitational force attracts objects to other objects. For us walking around on Earth, the acceleration due to gravity is one G. But say you're in a car going around a curve, people in the car feel their speed changing acceleration, and that feels like an intense force, more intense than the pull of Earth's gravity, which is keeping you stuck on Earth. And it is. It's more than 1G. Roller coasters can give you over 5G's and bobsledding can go just as high on Those tight turns in skeleton, the intense G force and positioning can even cause the athletes heads to hit the ice. And Peter McCarthy says that all of this is really rough on the body.

[E]

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

[C]

And remember, as Alia Snyder says, the brain is the central command system of the body.

[D]

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, you know, the spine and the rotation from that as well.

[C]

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 sub concussive 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.

[E]

Yeah, we put trek little sort of three axis 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 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.

[C]

What are you planning to do with the data?

[E]

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

[C]

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

[E]

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, there isn't.

[C]

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. For what have you seen sledhead do to the brains and bodies of your patients?

[D]

Over time there's a wide range of how sledhead can look. And you know, I think sledhead is a useful term for discussing kind of the phenomena 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 good concussion or TBI from a particularly bad crash.

[C]

Traumatic brain injury.

[D]

Tbi, Yes, a traumatic brain injury that there seem to be showing some reduced tolerance to those stress forces on the track. 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 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 susceptible to these broad non specific headache, fatigue, irritability, attentional difficulties afterwards.

[C]

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

[D]

Kind of, yeah. A wear and tear on the accuracy 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.

[E]

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 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 recovery, they need to be given sufficient time to actually recover.

[C]

Yeah, what it sounds like medically is happening is the sub concussive 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?

[D]

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 sub concussive. But that also comes to this idea of what do we do afterwards. And part of recognition is also the, the idea that it can be better, that this is not a 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. 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.

[C]

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?

[E]

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, time out, 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. 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.

[C]

That is. Aaliyah Snyder and Peter 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 athletes well being.

[D]

Thanks so much, Emily. It was a pleasure.

[E]

Yeah, thank you, Emily.

[C]

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 Sledhead and they didn't get back to us before publishing. If you like 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 Keeley was the audio engineer. I'm Emily Kwong. Thank you for listening to Short Wave from npr. See you next time.

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