A 48-hour race is a continuous timed event: the clock keeps running while you decide when to run, walk, eat, change gear, rest, and possibly sleep. That freedom is the appeal—and the reason a flexible plan matters more than a single pace or mileage target. This explainer covers the format; the 48-hour race guide collects training, sleep, nutrition, and the event calendar in one place.
The Format
Many 48-hour events use a short track, road, or trail loop, but course length, direction changes, timing rules, crew access, aid, and partial- lap credit vary. Read the organizer's current rules before building your plan. The winner is normally the athlete with the greatest recorded distance when 48 hours expire.
At the 48 heures de Royan in October 2025, the median of 38 results was 201.1 km and the middle half ran 161.4–222 km. At Across the Years in December 2025 the median of 53 results was 161.2 km, pulled down by runners who stopped once they reached 100 miles. We recommend 160 km as a first target and 200 km as the stretch; the records and more fields are on the 48-hour race guide.
| Question | 24-hour | 48-hour |
|---|---|---|
| When does the clock stop? | At 24 hours; personal breaks use race time. | At 48 hours; personal breaks use race time. |
| What should support cover? | One day-night cycle, with timing determined by the start. | Two day-night cycles, repeated resupply, and crew handoffs. |
| What must the rules explain? | Lap credit, re-entry, personal aid, and withdrawal. | The same questions, plus permitted sleep spaces and ongoing access. |
| Where to go next? | Choose a course and rehearse a full-day support routine. | Choose a course and rehearse restarts and second-day support. |
Stopped time comes off the clock. For 200 km, four stopped hours leave 44 moving hours and need 13:12 per km while moving; six stopped hours leave 42 and need 12:36 per km. For 160 km with six hours stopped, 15:45 per km is enough, which is an ordinary walking pace.
Compare the 48-hour calendar with the 24-hour calendar. Use the pace calculator for your own scenarios and the training guide for preparation.
What Changes After One Day
- Sleep pressure accumulates. Sleep loss can impair endurance performance, mood, vigilance, reaction time, and judgment.
- Small problems have longer to grow. Hot spots, chafing, cold stress, heat stress, and GI symptoms deserve early attention instead of an automatic gear or medication response.
- Food preference can change. Familiar alternatives in different flavors, textures, and temperatures make adaptation easier.
- Decision quality matters. A written plan and an observant crew member can catch unsafe changes that the runner misses.
How Much to Sleep
Our default for a first 48-hour race is 1–3 hours of sleep in total:
- Night one: no planned sleep; one 20-minute nap only if you nod off while walking.
- Night two: one 90-minute sleep between about 02:00 and 04:00, plus 20-minute naps as needed.
- Every stop: alarm set for 25 or 100 minutes, a crew member present for the wake-up, and a short walk before you rejoin the course.
Avoid 30–60 minute naps, which are the most likely to end in deep sleep and a slow, groggy restart. Sleep well in the week before the race; it does not let you skip sleep during it. The evidence and the budgets for other formats are in the sleep strategy guide.
Fuel and Fluid Over Two Days
Aim for about 50 g of carbohydrate an hour, with 30 g as the floor on bad-stomach hours. Plan 300–600 mg of sodium an hour, or 600–1,000 mg in heat. Over two days, sweet products wear thin: bring savory solids, warm soup, rice and potatoes, and one liquid carbohydrate you know you tolerate for when chewing stops appealing.
Drink to thirst, which for most runners is 450–750 mL an hour. The exercise-associated hyponatremia consensus identifies sustained overdrinking as the principal preventable risk and warns that sodium-containing drinks cannot make excess fluid safe. See the timed-race food planning guide and the hydration and sodium guide for practical guardrails.
Manage the Second Night Safely
The second overnight period combines the body-clock low with 40 hours of accumulated fatigue, and for most runners 02:00–05:00 is the hardest stretch of the race. Prepare the environment before dark: working lights and backups, warm and dry layers, an accessible rest space, familiar food, and written check-in rules.
Save caffeine for the nights: none in the first 10 hours, then about 50 mg an hour overnight, or one 1–2 mg/kg dose every two hours. Stop 2–3 hours before the planned sleep. Count coffee, cola, gels and tablets in the total. Caffeine does not replace sleep, and it is never a reason to keep going through the warning signs below.
Is the Format a Good Fit?
A 48-hour race may fit if you can answer these questions clearly:
- Have you built an appropriate endurance base without a current injury or unresolved illness?
- Have you practiced easy pacing, walking, fueling, foot care, darkness, and weather-specific gear?
- Do you know the event's medical, crew, sleep-area, and withdrawal procedures?
- Can you name the signs that will make you stop, rest, or seek help?
- Do you have safe transport and recovery plans after the event?
Previous 24-hour experience can be useful, but it is not the only path. Discuss major health concerns and medications with a clinician familiar with your history, and build the race plan with the 48-hour training guide and sleep strategy guide.
Sources
- Global Organization of Multi-Day Ultramarathonists — multiday race information and championship formats.
- 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.
- Lopes, T.R. et al. (2023) — How much does sleep deprivation impair endurance performance? A systematic review and meta-analysis. European Journal of Sport Science, 23(7), 1279–1292.
- 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.
- Hew-Butler, T. et al. (2015) — Third International Exercise-Associated Hyponatremia Consensus Statement.
Frequently Asked Questions
What pace do you need for 160 km in 48 hours?
An average of 3.3 km/h over the full 48 hours, including every stop. With 3 hours of sleep and 3 hours of other stops, that is 3.8 km/h while moving, or 15:45 per kilometre: a steady walk. 200 km needs 4.2 km/h overall.
What is the hardest part of a 48-hour race?
For most runners it is the second night, roughly 02:00 to 05:00, when the body-clock low lands on top of 40 hours of effort and little sleep. That is where we recommend taking the one planned 90-minute sleep.
Should I try a 48-hour race before a 6-day race?
Yes, we recommend it. A 48-hour race tests the second-night routine, sleep stops, foot care and crew handoffs that a six-day race repeats five times, at a third of the cost in recovery.