Most of the measurable damage from a 100-mile or 24-hour race clears in two to three weeks. Soreness goes first, speed returns next, and strength comes back last. The table gives the numbers from the studies, and the schedule below turns them into a plan. For what happens inside the body during the race itself, see what happens to your body during an ultramarathon.
Recovery Timeline: Day by Day
| When | What studies measured | What to do (our plan) |
|---|---|---|
| Finish to 24 hours | After a 166 km mountain race, knee-extensor strength was down 35% and calf strength 39%, and CK, a muscle-damage marker, rose from 144 to 13,633 U/L (Millet 2011). A 24-hour treadmill run cut knee-extensor strength by 41% (Martin 2010). | Get warm, eat, drink to thirst, and sleep. Walk only as needed. No NSAIDs. |
| Days 1–3 | In 72 Western States 161 km finishers, 400 m sprint time was still 26% slower than before the race on day 3. Runners with the highest CK recovered slowest (Hoffman 2017). | Walk 20–40 minutes a day. No running. |
| Days 4–7 | Soreness and fatigue were back to pre-race levels by day 5, but 400 m time was still 12% slower (Hoffman 2017). Across endurance events, muscle and kidney markers returned to baseline after a mean of 5.86 days (Rojas-Valverde 2021). Inflammation takes longer to normalize than muscle damage (Martínez-Navarro 2021). | First easy run of 20–30 minutes once soreness is gone and stairs feel normal, usually day 5–7. |
| Days 8–10 | In a placebo-controlled riboflavin trial with 32 Western States finishers, 400 m times in both groups were back to pre-race level by day 10 (Hoffman 2017, riboflavin trial). Most strength recovery after the 166 km race happened within 9 days (Millet 2011). | Easy runs every other day, building to 45–60 minutes. No intervals yet. |
| Days 11–16 | Leg strength and neuromuscular function were back to baseline by day 16 in the 11 runners followed after the 166 km race (Millet 2011). | One faster session after day 10, and a first long run after day 14. |
| Weeks 3–4 | The studies stop here, with the measured deficits closed by day 16. | Full training, if the faster session and long run felt normal. |
These studies followed mostly experienced, mostly male finishers of 100-mile-class and 24-hour races. Treat their numbers as the minimum for anything longer.
The First 24 Hours
- Get out of wet clothes and warm up before you stiffen and chill.
- Eat a normal meal with carbohydrate and 20–40 g of protein as soon as your stomach allows.
- Drink to thirst. Do not force fluid.
- Skip ibuprofen, naproxen, and other NSAIDs until you are urinating normally and your urine is pale. The kidney section below explains why.
- Sleep before you drive, and never drive drowsy.
- Take shoes and socks off carefully. Treat blisters with the blister management steps, which also list the signs of infection.
Return-to-Running Schedule
This is our recommendation for a 100-mile or 24-hour race, built from the timeline above. It brings volume back before intensity, because rapid jumps in training load are a recognized injury risk (Soligard 2016).
- Days 1–3: walk only, 20–40 minutes a day. Easy cycling or swimming is fine if it does not hurt.
- Days 4–7: first run, 20–30 minutes easy on flat ground, once soreness has gone and you can walk down stairs normally. That is usually day 5–7.
- Days 8–14: easy runs every other day, building to 45–60 minutes. No intervals, hill repeats, or races before about day 10, when 400 m speed had returned in the studies.
- Days 15–21: one faster session a week and one long run of up to half your usual long run.
- Weeks 3–4: full training, if the faster session and the long run felt normal.
If you fall behind the schedule, wait rather than skip ahead: if soreness is still there on day 7, the first run waits until it has gone. Runners with the most muscle damage recovered slowest in the Western States data. A race with a late collapse, a lot of downhill, or a very high CK reading calls for the slow end of each range.
48-Hour, 6-Day and Backyard Races
No study has tracked recovery after a 48-hour or 6-day race. The timelines below are our extrapolation from the 100-mile and 24-hour data, scaled for more hours on your feet and more lost sleep.
| Race | Walk only | First easy run | First hard session | Full training |
|---|---|---|---|---|
| 24-hour race or backyard ultra under 24 hours | Days 1–3 | Day 5–7 | After day 10 | Weeks 3–4 |
| 48-hour race or backyard ultra of 36–48 hours | Days 1–5 | Day 7–10 | After day 17 | Weeks 4–5 |
| 6-day race | Days 1–7 | Week 2 | After day 24 | Weeks 5–6 |
What Speeds Recovery and What Doesn't
Protein and Food
Eat normal meals with carbohydrate, and spread 20–40 g of protein every 3–4 hours through the day, plus 30–40 g of casein-rich food such as milk, cottage cheese, or Greek yogurt before bed. These are the International Society of Sports Nutrition's general recommendations (Jäger 2017), not results from ultramarathon trials.
Sleep
Expect to need extra sleep for several nights. In 13 runners tracked with wrist actigraphy through the 135 km and 217 km Brazil 135, mean sleep during the race was 97 minutes. Afterward they woke later, and total sleep in the following week trended higher than on the first night home, which suggests that sleep recovers with a delay (Daniel 2026). Our recommendation: allow 9 hours in bed for the first three nights. The sleep strategy guide covers sleep during the race.
Massage and Compression
They feel good and do little else. In a trial with 72 Western States finishers, a 20-minute massage or pneumatic-compression session lowered soreness or fatigue right afterward, but there was no difference from simple rest on days 1–7 (Hoffman 2016). In a follow-up with four daily treatments in 56 runners, soreness ratings and 400 m times were no better over 14 days, beyond short-lived fatigue relief (Heapy 2018). Book one if you enjoy it, but do not expect it to speed your return.
Painkillers
Avoid ibuprofen and other NSAIDs until you are urinating normally and your urine is pale. In a randomized trial during an 80 km desert-race stage, 52% of runners taking ibuprofen 400 mg every 4 hours developed acute kidney injury, against 34% on placebo. That is one extra case for every 5.5 runners treated, although the difference did not reach statistical significance (Lipman 2017). The trial tested use during the race. Applying it to the first days after the finish is our extrapolation, because kidney markers are highest right after the race (Rojas-Valverde 2021). If you need pain relief, ask a pharmacist or doctor which option suits you.
Illness, Heart and Kidney Markers
Colds. About one runner in four catches one. Of 106 Western States finishers, 24% reported an upper respiratory infection lasting at least 2 days within 2 weeks of the race, with symptoms for 5.4 days on average (Nieman 2006). Hold your place in the schedule until symptoms clear, and do not run with a fever.
Heart. Cardiac markers rise in many finishers. High-sensitivity troponin T was above the reference range after the race in 30% of 24-hour runners and 25% of 48-hour runners, and NT-proBNP rose 15-fold and 10-fold (Liu 2021). After UTMB, some cardiac and inflammatory markers were still raised 7 days later (Le Goff 2022). If you have a blood test or an ECG in the two weeks after a race, tell the clinician about the race.
Kidneys. Acute kidney injury is common at the finish: 42% (468 of 1,113 runners) across 28 ultra-trail studies (Lecina 2022). It usually resolves within a week (Rojas-Valverde 2021), but rare cases may progress to scarring and chronic kidney disease (Scheer 2022), which is one more reason to skip NSAIDs. For the long-term picture, read is ultrarunning bad for your body?
Sources
- Hoffman, M.D. et al. (2017) — Determinants of recovery from a 161-km ultramarathon. Journal of Sports Sciences, 35(7), 669–677.
- Hoffman, M.D. et al. (2017) — A Placebo-Controlled Trial of Riboflavin for Enhancement of Ultramarathon Recovery. Sports Medicine - Open, 3(1), 14.
- Millet, G.Y. et al. (2011) — Neuromuscular consequences of an extreme mountain ultra-marathon. PLOS ONE, 6(2), e17059.
- Martin, V. et al. (2010) — Central and peripheral contributions to neuromuscular fatigue induced by a 24-h treadmill run. Journal of Applied Physiology, 108(5), 1224–1233.
- Martínez-Navarro, I. et al. (2021) — Inflammation, muscle damage and postrace physical activity following a mountain ultramarathon. Journal of Sports Medicine and Physical Fitness, 61(12), 1668–1674.
- Rojas-Valverde, D. et al. (2021) — Exertional rhabdomyolysis and acute kidney injury in endurance sports: A systematic review. European Journal of Sport Science, 21(2), 261–274.
- Jäger, R. et al. (2017) — International Society of Sports Nutrition Position Stand: protein and exercise. Journal of the International Society of Sports Nutrition, 14, 20.
- Daniel, N.V.S. et al. (2026) — Tracking sleep in ultramarathon male runners before, during, and after a mountain race: Actigraphic evidence of sleep restriction. Sleep Health, 12(5), 858–865.
- Hoffman, M.D. et al. (2016) — A Randomized Controlled Trial of Massage and Pneumatic Compression for Ultramarathon Recovery. Journal of Orthopaedic & Sports Physical Therapy, 46(5), 320–326.
- Heapy, A.M. et al. (2018) — A randomized controlled trial of manual therapy and pneumatic compression for recovery from prolonged running - an extended study. Research in Sports Medicine, 26(3), 354–364.
- Lipman, G.S. et al. (2017) — Ibuprofen versus placebo effect on acute kidney injury in ultramarathons: a randomised controlled trial. Emergency Medicine Journal, 34(10), 637–642.
- Nieman, D.C. et al. (2006) — Relationship between salivary IgA secretion and upper respiratory tract infection following a 160-km race. Journal of Sports Medicine and Physical Fitness, 46(1), 158–162.
- Liu, C.H. et al. (2021) — Electrical Cardiometry and Cardiac Biomarkers in 24-h and 48-h Ultramarathoners. International Journal of Sports Medicine, 42(11), 1035–1042.
- Le Goff, C. et al. (2022) — Mountain Ultra-Marathon (UTMB) Impact on Usual and Emerging Cardiac Biomarkers. Frontiers in Cardiovascular Medicine, 9, 856223.
- Lecina, M. et al. (2022) — Acute Kidney Injury and Hyponatremia in Ultra-Trail Racing: A Systematic Review. Medicina, 58(5), 569.
- Scheer, V. et al. (2022) — Potential Long-Term Health Problems Associated with Ultra-Endurance Running: A Narrative Review. Sports Medicine, 52(4), 725–740.
- Soligard, T. et al. (2016) — How much is too much? (Part 1) International Olympic Committee consensus statement on load in sport and risk of injury. British Journal of Sports Medicine, 50(17), 1030–1041.
Frequently Asked Questions
How long does it take to recover from a 24-hour race?
About three weeks for most trained runners. After 100-mile-class races, soreness and fatigue were back to baseline by day 5, 400 m speed by day 10, and leg strength by day 16. A 24-hour run cuts knee-extensor strength by about 41%, similar to a 166 km mountain race. Walk on days 1–3, run easy from about day 5–7, skip hard sessions until day 10, and return to full training in week 3–4.
When can you run after a multiday race?
No study has measured recovery after a 48-hour or 6-day race, so our timelines are extrapolations from 100-mile data. After a 48-hour race, walk only on days 1–5 and start easy runs around day 7–10. After a 6-day race, walk only for the first week, start easy runs in week 2, avoid hard sessions before day 24, and expect full training around week 5–6.
What should you eat after an ultramarathon?
Eat normal carbohydrate-rich meals and spread 20–40 g of protein every 3–4 hours, with 30–40 g of casein-rich food such as milk or cottage cheese before bed (ISSN). Drink to thirst, and avoid ibuprofen and other NSAIDs until you are urinating normally.
Is it normal to get sick after an ultramarathon?
Colds are common: 24% of Western States finishers reported an upper respiratory infection within 2 weeks of the race. Hold your place in the return-to-running schedule until symptoms clear, and do not run with a fever. Chest pain, fainting, dark or scanty urine, or a one-sided swollen calf are not normal and need same-day medical care.
Do massage and compression boots speed ultramarathon recovery?
Only briefly. In a 72-runner Western States trial, a 20-minute massage or pneumatic-compression session eased soreness or fatigue right afterward, but there was no difference from rest on days 1–7. Four daily sessions in a 56-runner follow-up did not improve soreness ratings or 400 m times over 14 days.