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HomeRunningDiving into Ultramarathon DNF Knowledge – iRunFar

Diving into Ultramarathon DNF Knowledge – iRunFar

Some pals and I made the street journey to the 2016 Bighorn Path 100 Mile, and all of us obtained shirts with the course profile on the again. When considered one of my pals returned house with the shirt and a since-avenged DNF, his sons favored to level on the highest peak on the course profile and say: “That is the place you failed.” I believe they have been onto one thing — along with simply being exhausting on their dad — so let’s attempt to pinpoint what goes right into a DNF.

“Didn’t end” (DNF) is an end result that runners usually wish to keep away from, so it may be helpful to grasp the place the dangers of getting a DNF are larger. Are there explicit traits a race might need that may drive up the DNF fee? Are there factors in a race the place a DNF is extra doubtless? Strap in for a journey of discovery.

2017 Western States 100 - Jim Walmsley DNF

Jim Walmsley (left) ending his day on the river on the 2017 Western States 100, displaying that nobody is proof against the occasional DNF. Picture: iRunFar/Bryon Powell

The Methodology

This text attracts on two datasets: one composed of outcomes from 25 races, and a smaller dataset with 10 years value of splits for a specific race. For each datasets, I managed for distance by specializing in 100-mile races. Please don’t take that as a snub towards different race distances — we love all distances however should create knowledge boundaries someplace.

For the dataset composed of outcomes from 25 races, I deliberately selected races with some selection of their places, terrain, elevation, and begin instances (1). My dataset remains to be admittedly small, as a result of it’s comprised of simply 25 races and solely their outcomes from 2023. Nonetheless, it’s a superb start line for a just-for-fun evaluation that provides us one thing to debate with our pals on the following long term. I chosen races that have been:

  • A part of the World Path Majors
  • A part of the UTMB World Collection
  • On “UltraRunning Journal’s” checklist of the most important North American ultras in 2023, and/or
  • Occasions I’ve run personally and I wished to indicate them some love

The DNF fee for every occasion was calculated by dividing the variety of runners who DNFed by the variety of individuals who began the race. Runners who didn’t begin subsequently don’t issue into the DNF fee.

Do Sure Elements Affect DNF Charges?

Somewhat than preserve you in suspense, I’ll let you know proper now: “being the 2023 Western States 100” was the one issue that had a discernible impression on DNF charges on this explicit dataset. In 2023, over 85% of runners who began the Western States 100 crossed the end line in time to obtain their belt buckle. The proportion of runners who bought a DNF was 13.5%. That was an unusually excessive finisher fee: for the earlier 20 editions of the race, the typical DNF fee was 27%.

The 2023 version of Western States was thought-about a very mid when it comes to the climate forecast. There could also be different elements that give the occasion a better finisher fee (and decrease DNF fee) than another 100 milers.

Jennifer St. Amand - 2023 Western States 100 final finisher

Jennifer St. Amand, the ultimate official finisher of the 2023 Western States 100, who beat the cutoff by 21 seconds. Picture: iRunFar/Sarah Brady

For instance, Western States requires runners to qualify to run the occasion. The challenges of gaining entry to Western States additionally imply runners don’t have any assure of with the ability to strive once more subsequent yr — or ever — so the runners lucky sufficient to start out the race might be notably motivated to coach effectively.

Lastly, Western States maintains a waitlist, so runners who consider they received’t end the race have the choice of creating one other runner’s dream come true by withdrawing from the race upfront, so one other runner can have the chance as an alternative.

By means of some mixture of those elements, individuals within the 2023 version of Western States collectively crushed it.

Past this statement, there have been no apparent or statistically vital traits amongst any of the elements I examined. Whereas the races within the dataset had some notable variations amongst them, most had DNF charges inside a specific vary. The typical DNF fee within the restricted pattern dataset was 38%, and also you’ll see within the distribution chart under that almost all races had DNF charges in that ballpark.

Distribution of DNF Charges Among the many 25 Races within the Pattern Dataset

Diving into DNF Data - DNF Rate Distribution Bar Graph

Chart displaying the distribution of DNF charges among the many races examined.

DNF Charges by Complete Elevation Change

There isn’t any compelling or statistically vital pattern in how elevation change impacted the DNF fee in our dataset.

For instance, the Extremely-Path Snowdonia by UTMB 100 Mile had the best DNF fee in 2023 of races within the dataset, at 59%, and had 62,336 ft (19,000 meters) of elevation change. It eclipsed the Extremely-Path Kozciuszko by UTMB 100 Mile in each respects, as that race had simply 3,937 ft (1,200 meters) of elevation change and a DNF fee of 31% in 2023.

However there are each mountainous and relatively flat or hilly races throughout the 30 to 49% vary for DNF charges.

Emma Stuart - 2023 Ultra-Trail Snowdonia by UTMB - women's winner

Feminine winner Emma Stuart on the course of the 2023 Extremely-Path Snowdonia by UTMB 100 Mile. Tchnical terrain in addition to lots of elevation acquire doubtless contributed to the race’s excessive DNF fee. Picture: Guillem Casanova/UTMB

Correlation between DNF Price and Complete Elevation Change for Every Race

Diving into DNF Data - DNF Rate by Elevation

Scatterplot displaying the correlation between DNF charges and complete elevation change.

DNF Charges by Time Cutoff

Affording runners extra time to cowl 100 miles doesn’t appear to be a surefire strategy to scale back DNF charges. A 30-hour cutoff was the smallest period of time races on this dataset provided for runners to achieve the end line. Among the many races with that cutoff on this dataset — the South Downs Means 100 Mile, Western States 100, Hennepin 100 Mile, Javelina 100 Mile, Rocky Racoon 100 Mile, and Leadville 100 Mile — the DNF fee ranged from 13% proper as much as 56%.

Correlation Between DNF Price and Time Cutoff for Every Race

Diving into DNF Data - DNF Rate by Time Cutoff

Scatterplot displaying the correlation between DNF charges and time cutoffs.

DNF Charges by Race Begin Time of Day

In pre-race interviews for UTMB, North American athletes will typically consult with the problem of racing an ultramarathon with a night begin. Whereas the UTMB begins at 6:00 p.m. native time, the Rocky Racoon 100 Mile, for instance, begins at 6:00 a.m.

2017 UTMB start

The beginning of the 2017 UTMB. Many runners discover the 6 p.m. begin to be a problem. Picture: Kirstin Kortebein

Early begin instances have been pretty frequent among the many North American races on this dataset — although a lot respect to the Black Hills 100 Mile for letting runners sleep in earlier than their snug 10:00 a.m. begin time.

Whereas particular person runners are more likely to have opinions on the perfect time of day to start out a 100-mile race, the dataset didn’t counsel that begin time has an impression on DNF charges.

Correlation Between DNF Price and Begin Time for Every Race

Diving into DNF Data - DNF Rate by Start Time

Scatterplot displaying the correlation between DNF charges and begin instances.

Whither the DNF?

I used to be curious to know the place the “hazard zone” for dropping from a race is perhaps, so I pulled up the splits for the Superior Fall Path Race 100 Mile. I selected this race as a result of it’s a private favourite, and the race director publishes the race splits in a constant and accessible format. The 103-mile course is tougher within the second half, with probably the most technical terrains and largest climbs concentrated in that portion.

I’d like to broaden upon this evaluation in a future column and incorporate knowledge from extra races, however the knowledge from the Superior Fall Path Race 100 Mile confirms what I’m positive you intuitively suspected. You’re almost definitely to DNF your 100-mile race throughout that part of the race when your legs are drained, however you continue to have many miles to cowl.

I counted the entire DNFs, by assist station, for this race for the years the place splits can be found on-line — 2014 to 2023. I plotted them within the chart under to indicate the factors within the race which have the most important proportion of all DNFs.

As a technical be aware to my fellow superfans of this occasion, as a result of runners are strongly discouraged from dropping out on the distant Sonju Lake Street assist station and timing knowledge is commonly unavailable for that assist station, I mixed any identified DNFs for Sonju Lake Street with the DNFs on the subsequent assist station, Crosby-Manitou at mile 62.9.

Additionally be aware that every one DNFs for this race are marked to have occurred at assist stations.

DNFs on the Superior Fall Path Race 100 Mile, From 2014 to 2023, by Mile/Support Station

Diving into DNF Data - Superior Trail 100 Mile - DNF Rate by Mile-Aid Station

Graph displaying the place DNFs occurred on the Superior Fall Path Race 100 Mile, from 2014 to 2023.

However Why Did They DNF?

Outcomes and splits solely inform a part of the story with regards to a DNF. To essentially perceive why runners DNF, we have to have a look at the qualitative knowledge as effectively.

To the reduction of Instagram ultrarunning meme account @yaboyscottjurek, we don’t have to learn a bunch of nine-part race recaps on Instagram to grasp the explanations runners don’t end a 100 miler.

The American Path Operating Affiliation (ATRA) conveniently aggregated the experiences of roughly 1,200 survey respondents in a 2022 article on the subject. ATRA’s survey offered runners with a listing of causes they could DNF a path race of any distance, and runners might choose the entire causes that contributed to any of their previous DNFs. You possibly can see the leads to the desk under.

Reasons for DNFing table

Outcomes of a survey by the American Path Operating Affiliation about why individuals select to DNF a path race.

Closing Ideas

We might revisit this subject once more in a future column, as a result of there are extra questions I wish to reply. For instance, are DNF charges impacted by whether or not:

  • Runners want a qualifier to get into the race?
  • The race is kind of aggressive?
  • The race is a bucket-list kind race with a hard-to-enter lottery or vital and costly travels to?
  • Races that appeal to extra “repeat offenders” have decrease DNF charges, maybe as a result of extra individuals have prior expertise with the course?
  • There are notably troublesome climate or course situations, like excessive warmth, a giant storm, or extra snow or mud?
  • The race is lengthy or quick?

Moreover, I’d like to know if there’s a explicit time of day when runners are almost definitely to DNF, comparable to in a single day or maybe within the warmth of the day.

I think about many readers are taken with DNFs for a similar purpose I’m: We choose to complete our races. We hope that by understanding DNFs, we scale back the chance of it occurring to us.

Whereas I can’t think about many — if any — runners begin a 100-mile race with the intention of getting a DNF, ultrarunner, race director, and podcaster through the enterprise Ten Junk Miles Scott Kummer jogged my memory that the DNF represents a vital side of the ultramarathon.

I requested him concerning the DNF fee for the Badger Path Race 100 Mile, which he organizes. With 18 assist stations and a 38-hour restrict to cowl 100 miles on comparatively flat rail trails, it’s an occasion that we’ve beforehand described as “finisher-friendly.” The race nonetheless had a 26% DNF fee in 2023 — 34 DNFs amongst 133 individuals — which places its DNF fee throughout the identical vary because the occasions we examined above.

Bertha Lotje Woehl

Bertha Lotje Woehl, pacer Clara Beaudet, and assist station Captain Holly Lindroth on the 2021 Badger Path Race 100 Mile. The race is understood for its beneficiant cutoff instances. Picture: Will Harrison

However, as Kummer identified, among the runners interested in the Badger Path Race 100 Mile particularly select that race over different ultramarathons as a result of their probabilities of ending an occasion with much less beneficiant cutoffs on extra technical trails are too low.

Whatever the occasion or the terrain, many runners are drawn to occasions the place they’ve a legit likelihood at reaching their targets, however they’re challenged sufficient that getting a DNF stays a definite risk.

Talking for myself, it is a helpful reminder. When life will get busy and coaching falls by the wayside, it’s simple to get anxious concerning the growing odds that I received’t attain my race targets. Learning DNFs helps me make peace with my very own, and provides me a deeper appreciation for a way your complete level of coaching for a difficult race is to spend time pushing the boundaries of our potential, whereas repeatedly coming to phrases with these limits.

It applies to life exterior of working, too. Heck, I technically DNFed this text as a result of I missed a time cutoff for offering it to my editors and I nonetheless have to let you know about…

Name for Feedback

  • Do you think about the proportion of runners who DNF when judging a race’s problem?
  • What’s your private expertise with DNFs?
  • We might should take one other have a look at DNFs sooner or later. What different traits would you wish to dig into?


  1. In alphabetical order, the 25 races (all 100 milers) are: Bighorn Path, Black Hills, South Downs Means, Doi Inthanon Thailand by UTMB, Grand Raid des Pyrénées, Grindstone by UTMB, Hennepin, Istria 100 by UTMB, Javelina, Julian Alps Extremely-Path by UTMB, KAT100 by UTMB, Kullamannen by UTMB, Leadville, Mountain Extremely-Path by UTMB, Good Côte d’Azur by UTMB, Québec Mega Path, Rocky Raccoon, Run Rabbit Run, Superior Fall Path Race, Path Alsace Grand Est by UTMB, Extremely-Path Cape City, Extremely-Path Kosciuszko by UTMB, UTMB, and Western States.

Jason Miles
Jason Miles
Join the incredible Jason Miles as he defies all limits, running for days on end. Prepare to be amazed by his extraordinary endurance and unyielding determination!


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