The Short Answer
Sleep strategy is one of the defining differences between multiday formats. Up to about 30 hours you can get through on no sleep; beyond that, cumulative sleep loss degrades judgment and coordination faster than it saves time. So a 24-hour race is normally run awake, a 48-hour race needs a nap plan, and a 6-day race needs a nightly sleep block. Arrive well rested, but do not expect pre-race sleep to cancel what you lose during the event.
Sleep by Race Format
| Format | Do runners sleep? | What works |
|---|---|---|
| 24-hour race | Usually not | Stay awake; take a 10 to 20 minute safety nap if you are weaving or hallucinating |
| 48-hour race | Yes, briefly | One or two 20 to 30 minute naps during the second night, rehearsed in training |
| 6-day race | Yes, every night | A 2 to 4 hour block at the same time each night, plus 15 to 30 minute daytime naps as needed |
| Backyard ultra | Only in scraps | Finish loops in 45 to 50 minutes to leave 10 to 15 minutes; lie down with an alarm, but expect dozing rather than sleep |
| Stage race | Yes, between stages | Protect the overnight window: eat, treat feet, and get to bed early rather than socialising |
How to Nap in a Race
Keep naps short or make them a full cycle. Ten to 25 minutes keeps you out of deep sleep, so you wake reasonably clear; 30 to 60 minutes often drops you into deep sleep and you wake heavy and confused. If you have the time, as you do in a 6-day race, a 90-minute or longer block lets you complete a cycle. Sleep warm, dark, and horizontal: a cold or sitting-up nap gives little back. Set two alarms or hand the wake-up to your crew, and give yourself ten minutes of walking before you decide whether the nap worked. The multiday sleep strategy guide has a worked plan and crew checklist.
The Science of Sleep Deprivation in Ultras
Sleep loss combined with prolonged exercise impairs attention, reaction time, judgment, and safe movement, and the effect compounds the longer you go. In Kishi and colleagues' survey of 1,154 mountain ultramarathon finishers, in-race sleep became common once events stretched past a day, and it was mostly taken as short naps. Hurdiel and colleagues measured the cognitive cost at UTMB: reaction times and vigilance fell substantially in runners who had been awake through the night. A nap restores some of that, but temporary grogginess after waking is normal. Do not step back onto traffic or technical terrain until you can walk a straight line.
Sources
- Kishi, A. et al. (2024) — Sleep and Ultramarathon: Exploring Patterns, Strategies, and Repercussions of 1,154 Mountain Ultramarathons Finishers. Sports Medicine - Open, 10(1), 34.
- Guilherme, L.Q. et al. (2026) — The Role of Sleep on Physical and Cognitive Performance of Ultra-Endurance Athletes: A Systematic Review. Journal of Clinical Medicine, 15(4), 1398.
- Hurdiel, R. et al. (2015) — "Combined Effects of Sleep Deprivation and Strenuous Exercise on Cognitive Performances During the Ultra-Trail du Mont-Blanc." Journal of Sports Sciences, 33(7), 670–674.