The Short Answer
Sleep strategy is one of the defining differences between multiday formats. There is no safe 30-hour cutoff: sleep loss can impair judgment and coordination earlier, depending on prior sleep and time of day. So a 24-hour race is sometimes run without a planned sleep stop, but still needs a rest option; 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? | Our default |
|---|---|---|
| 24-hour race | Usually not | Stay awake; take a 10–20 minute nap if you get drowsy. Hallucinations or confusion mean stop and get assessed. |
| 48-hour race | Yes, briefly | 1–3 hours in total: a 20-minute nap on night one if drowsy, then one block of about 90 minutes on night two |
| 6-day race | Yes, every night | A 2–4 hour block every night from night one, plus 20-minute daytime naps as needed |
| Backyard ultra | Only in scraps | Finish loops in 45–50 minutes to leave 10–15 minutes; lie down with an alarm and a crew wake-up, 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
Our default is a 20-minute nap (alarm at 25 minutes), or a longer block of about 90 minutes in races of two days or more. No alarm setting guarantees a clear-headed restart, especially after severe sleep loss. Use a warm, sheltered rest area, set two alarms or give the wake-up responsibility to crew, and allow time to wake fully. Check speech, orientation and balance before returning to the course. 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.