Picture a mountain checkpoint at 2am.
A runner arrives feeling sick, struggling to stay warm and increasingly unsteady on their feet. They have been drinking throughout the race and are determined to carry on.
Now, you have limited kit, another checkpoint several kilometres away and a patient who has spent months preparing for this moment.
Before they leave, you need to work out what is happening, and whether continuing is safe.
Endurance event medicine brings familiar clinical problems into environments where assessment, treatment and evacuation can be difficult. Symptoms overlap, conditions change and an athlete’s determination to finish can make an already complicated conversation… harder.
For the medical team, five decisions help bring that assessment into focus.
(All sources at the end of this post).
1. Is the athlete coping, or are they deteriorating?
Fatigue and discomfort are part of endurance racing. That can make it difficult to recognise when an athlete needs more than a rest and some encouragement.
Start with what has changed. Is this how they usually feel during a long race? When did the symptoms begin? Are they becoming worse? Can they describe what has happened clearly, and does their account match what their support crew or checkpoint volunteers have seen?
An experienced runner may be very good at managing discomfort. Their experience is useful information, but it should sit alongside your assessment rather than replace it.
Repeated observations matter, particularly when the first assessment does not explain the presentation. Changes in behaviour, coordination or consciousness require attention, even when the athlete insists they are “simply tired”.
Don’t forget, the setting matters too. Someone resting in a sheltered checkpoint is facing a different situation from someone about to spend another two hours moving through exposed terrain. Your decision needs to account for both their current condition and what comes next.
2. What is causing the collapse?
A runner who collapses after stopping, particularly at the finish line, may have exercise-associated collapse (EAC), commonly caused by transient postural hypotension. However, more serious causes, including cardiac arrest, exertional heat stroke and exercise-associated hyponatraemia, must be considered before settling on that explanation.
Begin with a structured assessment and address immediate threats to life. Avoid allowing the race setting to narrow the differential too early.
Confusion or altered consciousness is particularly concerning. In exertional heat stroke, neurological disturbance occurs alongside excessive core temperature. The Wilderness Medical Society recommends rectal temperature as the preferred practical field measurement; oral, ear and forehead readings can be misleading.
When exertional heat stroke is suspected, rapid active cooling should not be delayed while waiting for temperature confirmation. Cold-water immersion is a recommended cooling method where the team can deliver it safely while maintaining appropriate monitoring and airway care.
Exercise-associated hyponatraemia can also cause vomiting, confusion and seizures. Point-of-care sodium testing can help distinguish it when available, but limited diagnostics make a careful history and early escalation especially important.
3. Will giving fluids help?
It is easy to associate an unwell runner with dehydration, and that assumption can lead to the wrong treatment.
Exercise-associated hyponatraemia, or EAH, involves a low blood sodium concentration during or shortly after exercise. Sustained overdrinking is a major preventable risk factor. In fluid-overload EAH, further hypotonic or isotonic fluids can worsen the condition.
Ask what the athlete has actually consumed, how much and over what period. “I’ve been keeping hydrated” tells you very little without those details.
For prevention, Wilderness Medical Society guidance supports drinking to thirst or estimating individual fluid needs during training. Sodium supplements do not prevent EAH if excessive drinking continues.
The practical lesson is to assess before defaulting to fluid replacement. Suspected EAH needs management guided by the athlete’s clinical condition and the event’s protocols. Confusion, seizures or reduced consciousness require urgent treatment and escalation.
Make the suspected diagnosis explicit during handover so the next team understands the risks of routine fluid replacement.
4. Can they safely continue?
This can be the most difficult conversation of your shift.
The athlete may have travelled a long way, raised money or spent years trying to secure a place. Stopping can feel devastating, particularly when the finish seems close.
A useful assessment considers how symptoms are progressing, how they affect function and whether the athlete can safely manage the next section. An increasingly altered gait, inability to bear weight or significant focal pain warrants further assessment rather than reassurance based on determination alone.
Severe muscle pain, marked weakness or dark urine should raise concern for exertional rhabdomyolysis and possible kidney complications. Dark urine alone is not diagnostic, and its absence does not exclude the condition. Assessment should consider the clinical picture alongside blood tests, including creatine kinase and renal function, and urinalysis. These warning signs should not be dismissed as ordinary post-race soreness.
Gastrointestinal problems deserve attention too. In a questionnaire study of the 161 km Western States Endurance Run, 96% of the 272 respondents reported gastrointestinal symptoms. Among respondents who did not finish, 35.6% said these symptoms contributed to their withdrawal.
That finding comes from one race, but it illustrates how much apparently routine symptoms can affect an athlete’s ability to continue. Persistent vomiting, for example, needs consideration alongside their observations, fluid history, energy intake and wider clinical picture.
Explain your concerns in terms the athlete can understand: what you have found, what might happen if they continue, and what support is available. Follow the event’s withdrawal and escalation procedures, and document the assessment and discussion.
5. Can the event support the plan?
A clinical decision needs a workable plan behind it.
Before race day, the medical team should understand the route, likely hazards, available equipment, communication systems and evacuation arrangements. Consensus guidance for remote ultra-endurance events recognises that medical provision must account for both common presentations and potentially life-threatening emergencies.
At a checkpoint, that becomes very practical.
Who can you contact? Where can the athlete be observed? How will they reach further care? What happens if the weather closes in or another casualty needs the same resources?
These questions belong in planning and briefing, while there is time to resolve them.
Conditions will also change during the event. The team needs a way to reassess risk, communicate concerns and adapt its response as the race develops.
Your own team’s fatigue matters within that planning too. Clear roles, reliable handovers and opportunities to rest help clinicians maintain effective care through a long event.
Preparing for the next checkpoint
Working in endurance medicine means combining clinical assessment with an understanding of the course, the athlete and the resources around you. Knowing when to observe, treat, escalate or recommend withdrawal is central to the role.
World Extreme Medicine’s Endurance Medicine Course brings those decisions into practical teaching, workshops and simulations in Chamonix. The programme covers environmental illness, hydration and nutrition, musculoskeletal and skin assessment, cardiac and respiratory presentations, medical planning and communication under pressure.
It also explores the conversations that come with the job, including supporting an athlete when their race needs to end.
Clinical note: This article provides an educational overview for healthcare professionals. Assessment and treatment should follow current guidance, the event medical plan, local protocols and the clinician’s scope of practice.
References
- Exercise-associated collapse: an evidence-based review and primer for clinicians. British Journal of Sports Medicine, 2011.
- Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Heat Illness: 2024 Update. Wilderness & Environmental Medicine, 2024.
- Wilderness Medical Society Clinical Practice Guidelines for the Management of Exercise-Associated Hyponatremia: 2019 Update. Wilderness & Environmental Medicine, published 2020.
- Clinical Practice Guideline for the Management of Exertional Rhabdomyolysis in Warfighters. CHAMP and collaborating organisations, 2025. Developed for a military population; referenced here for recognition of warning signs.
- Gastrointestinal distress is common during a 161-km ultramarathon. Journal of Sports Sciences, 2015.
- Medical services at ultra-endurance foot races in remote environments: medical issues and consensus guidelines. Sports Medicine, 2014.