Managing sleep during an ultra-endurance event like the UTMB® is always challenging. It depends on your experience with this type of race, your training plan, and your individual sensitivity to sleep deprivation. Here is our advice for managing sleep deprivation before, during, and after the race.
Why is sleep deprivation so severe on the UTMB®?
Ultra-endurance events lasting over 24 hours subject athletes to sleep deprivation that can cause severe drowsiness, coupled with cognitive and sometimes motor impairment. On the UTMB® 2026, with its cut-off time set at 46h45, active sleep deprivation can range from 20 hours for elite runners to nearly 47 hours for back-of-the-pack competitors.
The scientific community agrees on the direct link between sleep and performance: sleep deprivation impairs cognitive function and lengthens the recovery time needed after the race.
The issue is significant enough to warrant on-site scientific research. Since 2013, a research team from the Université du Littoral Côte d'Opale has been conducting a study on sleep and alertness during the UTMB®, using accelerometers and three-minute reaction time tests at aid stations in Courmayeur, Champex, Trient, and Vallorcine. Participation is voluntary and open to registered runners.
Our sleep management strategy
Setting out to run through two consecutive nights cannot be improvised. You need a sleep management strategy that is fundamentally different from single-night ultra races.
Before the race
- Sleep as much as possible in the weeks leading up to the race, ideally at least 8 hours per night
- Define your sleep strategy based on expected race duration and your personal experience
- Test your nap plan during training, not on race day
During the race
- Prioritise sleeping at night and in the early afternoon, when alertness naturally dips
- Choose low-altitude, quiet rest areas for naps
- Take short power naps, 10 to 20 minutes depending on your needs
- Take a first nap early in the race, on the very first night, rather than waiting for complete exhaustion
- On the second night, plan more frequent naps: if drowsiness returns less than three hours after the previous nap, it is a clear sign to stop again rather than pushing through
Once your plan is set, try to stick to it: if a nap is scheduled for 21:00, do not delay it to 22:00 for tactical race reasons. If severe drowsiness hits, do not hesitate to take an immediate nap, even extending it up to 30 minutes: heavy sleep debt will hurt your performance anyway, and time "lost" is almost always recovered later.
After the race
Never drive immediately after finishing. Have someone else drive or plan recovery time before setting off, following road safety guidelines: stop at least every 2 hours, and nap at a rest area at the first signs of drowsiness. Ideally, spend time recovering, stretching, eating a solid meal, and sleeping for at least 5 hours before undertaking any other activity.
Hallucinations and warning signs: when to stop
Past a certain threshold of deprivation, typically starting from the second night, some runners may experience visual or auditory hallucinations caused by exhaustion. This is a well-known, thoroughly documented phenomenon in ultra-endurance. These episodes are a strong signal that it is time to stop: do not attempt to fight through them by continuing to run. A short nap, even 10 to 15 minutes, is usually enough to clear these symptoms and get moving again safely.
One critical boundary to keep in mind, however: if confusion, disorientation, or balance issues persist after a rest and food intake, it is no longer simple drowsiness. Report to the medical tent at the next aid station. These symptoms can also indicate hypoglycaemia, hyponatraemia, or early-stage hypothermia, which require medical assessment rather than a nap.
Frequently Asked Questions
Do runners sleep during the UTMB®?
Yes, the vast majority of runners take at least one short nap during the race, especially from the second night onwards. It is never mandatory, but strongly recommended for both safety and performance.
How long should a nap last during the race?
From 10 to 20 minutes in most cases, up to 30 minutes in cases of severe drowsiness. Beyond that, waking up becomes harder and getting back into the rhythm more difficult.
How many hours should you sleep before the race?
It is recommended to sleep at least 8 hours per night in the weeks leading up to the race to build up a sufficient sleep reserve before the race-induced sleep deprivation.
Are hallucinations dangerous?
They are common in ultra running and typically vanish after a short nap. However, persistent confusion or disorientation after resting warrants an immediate visit to the medical tent: other underlying medical conditions may be at play.
