DNF stands for ‘did not finish’ – the acronym no ultrarunner wants assigned to their race result. For amateurs, DNFing is loaded with emotion – but attrition rates are extremely common
Drenched, freezing, utterly miserable and with a GI catastrophe ready to blow, my internal conflict of quit/don’t quit was in full force. I was at about kilometre 56 of my 100km ultramarathon. After a cascade of bad decisions and worse weather, totally wretched, I shuffled and sobbed my way through the dark to the next checkpoint. By the time I got there at 62km, the resignation of dropping out had settled in. Months and months of training had come to nothing.
Inside the checkpoint, soaked runners and their besieged crew were crowded into what resembled a field hospital triage unit. In the chaotic throng I found my crew, slumped down on to a bench and said: I’m pulling out.
Beneath the emotional turmoil remained a rational calculation. With another 40km still to go in appalling weather, unable to keep nutrition down, if I kept going and things got worse, which they inevitably would, I wasn’t just risking myself, I was risking whoever may have to help me. Full of self-loathing, there wasn’t really any other option. One thought remained. It’s just a run.
DNF stands for “did not finish” and it’s the acronym no ultrarunner wants assigned next to their race result. For amateur runners, it’s so loaded with emotion, it is rarely spoken about. Failure, disappointment, regret, shame and guilt all jostle for position in the mind of a broken runner in the days after a DNF.
But a DNF is extremely common. Sometimes it’s the result of a single factor, like a race-ending injury, but more commonly it’s a convergence of elements, physical and psychological. DNF rates vary wildly from race to race, but it’s not unusual for an ultramarathon to have an attrition rate between 15% and 40%, depending on conditions. The 2026 Ultra Trail du Mont Blanc, which took place on 28-30 August, had a DNF rate of 30%, while in 2025 when the weather included driving rain, strong winds and biting cold, the rate was 35.8%.
An ultramarathon is the culmination of months, if not years, of training and planning. In the lead-up, you often spend between 10 and 20 hours a week running, frequently before dawn or at night, usually on your own. For months, you fit it around work and family, miss out socially, become more than mildly obsessed with food and try not to completely alienate the significant people in your life. The investment of time and money you’ve committed to compounds constantly in your head.
In 2023, Robbie Williams, a civil engineer from Melbourne, DNFd at Tarawera Ultra-Trail in the Miler (100 miles, 160km), which is held on New Zealand’s North Island, about 20km south-east of Rotorua. The race had been in his calendar for three years, since it had been cancelled twice due to Covid-19. By the time he reached the start line, he estimates the cumulative training hours were in the hundreds, to say nothing of the burden of anticipation.
An experienced athlete, this was his first attempt at the 160km distance. About 18 hours into the race, he was feeling increasingly unwell. Light-headed, nauseous, beginning to stumble, he made it to the checkpoint at 105km around midnight, by that time slightly delirious.
Trying to pinpoint why he was in such a state, he realised he’d substantially overdosed the salt tablets he’d been taking to regulate his electrolytes. Over the course of several hours, he’d ended up extremely dehydrated and hypernatremic (high blood sodium).
Confused about his timings, irritable and extremely fatigued – all symptoms of hypernatraemia – he pulled out. The next day he realised if he’d let himself sit down and recover for a couple of hours, he could have gone on to finish, probably close to his goal time.
He says: “I was massively disappointed in myself. Full of ‘what ifs’ for a long time. I wouldn’t say it was as bad as a breakdown, but it affected me very deeply. When you start thinking about how other people see you, it’s really dangerous territory.”
DNFing a race can be due to psychological factors as well as physical; or a combination of both. Sarah Houston was in the middle of a relationship separation when she signed up for a 100km ultra; but as race day drew closer, that changed. The 42-year-old gym owner and personal trainer had completed the distance several times before, and knew the time and planning involved in training was considerable.
“With so much happening in my life, the original goals had diminished so much I was left wondering why I was doing it,” she says.
“While the schedule gave me much-needed structure during a very turbulent time, I actually didn’t have the emotional bandwidth you need to sustain that prolonged period of intense training.”
