Summary of How do extreme G-forces affect Olympic bobsledders?

Overview of Shortwave — How do extreme G-forces affect Olympic bobsledders?

This NPR Shortwave episode examines "sled head": the dizziness, nausea, cognitive problems and long-term brain effects reported by bobsled and skeleton athletes after repeated high G-force runs. Through interviews with former athlete–now–neuropsychologist Aaliyah Snyder and neurophysiologist Peter McCarthy, the episode explains what sled head looks like, what limited research so far shows about the mechanics and risks, and what scientists recommend to make sliding sports safer.

Key points and main takeaways

• "Sled head" describes post-run symptoms (dizziness, nausea, headaches, fatigue, attention problems, irritability) that can accumulate from repeated high G-force exposure and sub-concussive impacts in bobsled and skeleton.
• Helmets protect the skull from external impacts but cannot stop the brain moving inside the skull; that internal movement (and stretching/tethering forces) can cause concussive and sub-concussive brain injury.
• Existing research is sparse. Teams of scientists are beginning to gather objective measurement data (helmet sensors) to quantify head acceleration, vibration frequencies, and cumulative exposure.
• Culture and incentives (athletes hiding symptoms to avoid being benched) and lack of objective exposure limits hamper athlete protection.
• Possible protections include objective exposure monitoring (sensors/exposure meters), enforced rest thresholds, and multi-modal rehabilitation (cognitive, autonomic, physiological training), not just a "push through" mentality.

What sled head is (symptoms & mechanisms)

• Common symptoms:
  • Dizziness and balance problems
  • Nausea and sensitivity to light
  • Headaches, fatigue, irritability
  • Problems concentrating and other cognitive deficits
• Mechanisms discussed:
  • High G-forces on tight turns cause the skull and brain to accelerate differently; the brain can "squidge" against the skull and be stretched/tethered.
  • Vibrational frequencies picked up during runs are mostly below ~50 Hz; low-frequency vibrations transmit more movement into the head.
  • Sub-concussive impacts and repeated exposure without adequate recovery may lower tolerance to further G-stressors, triggering wider autonomic and cognitive dysfunction.

Evidence and measurement

• Researchers have placed three-axis sensors inside helmets to record head motion, direction, and frequency content during runs.
• Preliminary findings show a range of vibration frequencies with a majority under 50 Hz — frequencies that effectively transmit movement to the head.
• Data have been reported to sport medical committees but overall evidence remains limited and "unquantified" in terms of clear exposure limits or thresholds.

Athlete experiences and clinical observations

• Aaliyah Snyder: former competitive skeleton athlete who experienced repeated symptoms and multiple concussions that ultimately led to medical retirement; she now trains as a neuropsychologist studying sliding-sport brain health.
• Clinical patterns:
  • Some athletes recover after rest and rehab; others show decreased tolerance (even to routine stresses like standing) after a major concussion followed by continued exposure.
  • Autonomic nervous system dysregulation is observed (altered pupil responses, heart rate/breathing patterns), which links to cognition and symptom persistence.
  • Athletes often under-report symptoms to avoid missing training or selection — creating a barrier to timely care.

Limitations, gaps, and stakeholder response

• Major gaps:
  • Few longitudinal studies on cumulative sub-concussive exposure in sliding sports.
  • No widely accepted objective exposure thresholds or standardized return-to-play protocols tailored to bobsled/skeleton.
  • Sparse published literature and limited institutional action so far.
• The producers reached out to International Bobsleigh & Skeleton Federation and national bodies (USA, UK, Canada) for comment; no responses were received before publication.

Recommendations and what scientists propose

Short-term

• Deploy objective helmet sensors/exposure meters broadly so cumulative head acceleration/vibration can be measured per run and per week.
• Use objective data to define exposure caps or rest triggers (e.g., "you’ve reached your weekly exposure—take a rest period").
• Improve medical screening and encourage non-punitive reporting so athletes feel safe reporting symptoms.

Long-term / clinical

• Fund longitudinal studies that link measured exposure to cognitive and autonomic outcomes.
• Develop sport-specific rehabilitation protocols that combine:
  • Cognitive training
  • Autonomic re-regulation exercises
  • Physiological and behavioral interventions
• Change culture away from "push through it" to recovery-focused care that treats the brain as a plastic, responsive organ.

Notable quotes from the episode

• "The brain basically squidges up against the skull." — Peter McCarthy
• "Everybody's kind of a little bit concussed all the time" (what athletes were told historically) — paraphrase of common culture around sled head.
• "You cannot rely on anybody to actually observe and say, time out, come here. You need to have an objective measurement." — Peter McCarthy

Bottom line

Sled head is an under-researched but common concern in bobsled and skeleton. Preliminary helmet-sensor data and clinical observations suggest repeated sub-concussive G-force exposure can produce lasting brain and autonomic dysfunction, especially when athletes are pressured to continue training. Scientists recommend objective exposure monitoring, enforced rest thresholds, better reporting culture, and integrated rehabilitation approaches; substantial research and policy work remain necessary to protect athlete brain health.