How to Know When to DNF

It can be a difficult decision to drop out of a race, so we asked experts to share some ways to make that choice more objective

Photo: Daniel Petty/The Denver Post via Getty Images

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When an athlete stands on the start line of a race, there are always feelings of possibility, opportunity, and nerves, no matter the distance. The hours of training and preparation that go into making it to the start line are an endurance event on their own. 

On average, it costs nearly $400 to register for a 100-mile trail race, and that’s before booking any travel or lodging for race week. A good pair of trail shoes can set an athlete back anywhere from $100 to into the $200-range, and other equipment such as hiking poles, headlamps, sports nutrition, and technical clothing mean that it’s easy to spend thousands of dollars on training and racing before you even reach a start line. 

Most ultramarathon training plans involve running 35-50 miles a week, which depending on an athlete’s abilities, can take 10-15+ hours spread over seven days. When tallied up over six months, an athlete might spend upwards of 300 hours training for an ultra. 

Suffice it to say, the investment just to reach the start line of an ultramarathon is tremendous. 

The huge emotional and physical investment that an athlete makes to be able to race means that very few people arrive at a start line thinking that they won’t finish a race. And yet, races like the Badwater 135 and the Leadville 100 Trail Run have notably high “Did Not Finish” (DNF) rates each year: Badwater 135 sees DNF rates of up to 40%, and in 2023, the Leadville 100 Trail Run had a DNF rate of about 56%

With the large financial and personal investment required to prepare for an ultra, it can seem incongruous that some of the most famous trail races in the world have such significant drop rates year after year. This begs the question: why? 

RELATED: How to DNF Your Next Ultra

Why Runners DNF

Athletes who decide to drop from a race typically do so because of injury, illness, or mental challenges. No matter the cause, DNF’ing can be a confusing and heartbreaking decision when the lure of reaching the finish line can cloud one’s judgment. 

According to one 2022 1200-person study by the American Trail Running Association, the top reasons for DNF’ing a trail race included getting injured during the race, not making a cutoff time mid-race, or getting sick during the race. 

Data from Western States shows that 54% of 2023 racers and 69% of 2022 racers who DNF’d did not use a coaching service, and 59% of 2023 racers and 68% of 2022 racers who DNF’d did not attend Western States’ spring training camp, which allows racers to familiarize themselves with the course. While not always the case, data like this can imply a connection between underpreparedness in training and DNF’ing.

“Endurance athletes in general—whether a runner, triathlete, cyclist, or otherwise—know how to suffer, and we are willing to suffer,” says Dr. Jeffrey Krebs, a California-based board-certified internal medicine doctor with decades of experience in treating both athletes and critically ill patients. “We are so willing to suffer that we often will push ourselves to the max, even when in the back of our mind we know we shouldn’t.” 

The best way to make the call to DNF, or not, is to understand what situations and symptoms call for throwing in the towel and which can safely be managed without dropping out of a race. Thinking through these scenarios before you reach the start line will help you, your crew, and your pacers have a plan of action regarding DNF’ing ahead of time, without letting snap decisions cloud decision-making come race day.

Mental Factors

Maryland-based Shannon Mulcahy is a sports psychologist who has worked with numerous trail runners on everything from pre-race nerves to managing mid-race stress. Mulcahy shares that starting race-day with an optimal mindset can help prevent the onset of unfavorable mental states later. 

“Everyone is different, but you want to find a sweet spot of emotions before the race,” Mulcahy says. “I describe this as feeling confident, excited, maybe even a little relaxed, and with a healthy amount of nerves.” 

Mulcahy notes that starting the race feeling either too jittery, too sleepy, or too unmotivated can spell trouble later on. 

“There is absolutely a point at which you can be overly anxious or not focused enough on the task at hand,” Mulcahy says. “These states can make it difficult to remember why you wanted to do the race in the first place, making it hard to enjoy the moment and the race itself.”

To find your optimal pre-race mindset, Mulcahy recommends thinking back to some of your best performances and recounting how you felt and what you did before them. For some, it might be listening to a specific playlist or eating certain foods. For others, it might be having alone time before the gun goes off. Creating a repeatable pre-race routine that feels good can be key to starting the day off on the right foot. 

As the race progresses, especially in longer races, the mind can take a toll from the stress of the day and the thousands of micro-decisions, and an athlete must begin to carefully consider if they are well enough mentally to continue the race.

“One of the checkpoints I tell my athletes around mental states and checking in with yourself is if an athlete is starting to make a lot of mistakes,” Mulcahy says. “If you’re noticing that you’re tripping over less technical sections or forgetting to eat or drink, this can be a sign that your mind is beginning to fatigue.”

Another sign of potentially DNF-worthy mental challenges mid-race can be drastic changes in mood. 

“When an athlete starts to have an emotional response that is inappropriate for the situation, they or their crew need to pay close attention,” Mulcahy says. “For example, if an athlete forgets to take an extra gel at an aid station and starts sobbing about it, this can be a sign that their blood sugar is too low or that their mind is experiencing extreme duress.”

Mental fatigue in an endurance race is inevitable, but there are a couple things Mulcahy recommends to prevent the onset of mental mistakes or mood swings that could result in a DNF. 

The first is to identify parts of the race where you can “zone out a bit,” according to Mulcahy. These parts might be a flatter or non-technical section of the race, or sections you’ve run before and know well. 

If your race involves a crew or pacers, making a plan for each aid station with them before the race can also give your brain a break during aid stations or meetup spots, putting the onus on the support crew to make decisions for you. 

Mulcahy strongly advises athletes to create a “DNF plan” before race day, too.

“Creating a DNF plan involves mapping out what emotions, mental states, or physical situations should result in DNF’ing a race,” Mulcahy says. “Planning out what scenarios constitute a DNF for you before you’re caught up in the excitement of race day can help make a DNF decision more objective if that time comes.”

Share this DNF plan with your support crew so they can reinforce your decision to push on or call it a day when the going gets tough. 

The mind is a powerful tool that can make or break your race day. But to have a strong mind, you also need to have a strong body across the miles. 

RELATED: How Sports Psychologists Define Mental Toughness

Physical Factors

It’s easy to decide to forgo a race when obvious signs of physical illness or injury are present, like the flu or a broken bone. It is a less obvious decision to drop out of a race when physical discomforts like gastrointestinal (GI) distress or joint pain set in mid-competition. 

Dr. Jenni Vanos  is an associate professor in the School of Sustainability at Arizona State University, where she studies the effects of extreme heat and air pollution on vulnerable populations, including athletes. 

“I consider athletes to be a vulnerable population because athletes are willing to push themselves even in extreme environments like excessive heat,” Dr. Vanos says. “Sometimes we are our own worst enemies, like still going out for a run when a storm is coming, thinking we can beat the storm. As athletes, our own motivation can get in the way of logic.”

Dr. Vanos shares that one of her greatest concerns is for athletes who try to suffer through the initial signs of heatstroke without recognizing that they are in danger. 

She elaborates to say that one initial sign of heatstroke is the onset of severe GI issues. 

It can be difficult to assess this early warning sign as GI distress can occur for many reasons, but according to Dr. Vanos, “heatstroke begins in the gut.” She recommends that, at a minimum, if you’re feeling too hot and have rapid-onset GI issues, stop in the shade to cool down and consume fluids. 

“Endurance athletes have to know their bodies well,” Dr. Vanos says. “If you suddenly get GI issues that are totally out of character for you, pay attention to them. Athletes have to be the ones to make the call if GI distress symptoms are mild or if they feel concerning.”

If GI issues worsen or cascade into other symptoms of heatstroke—confusion, headache, lack of sweat, or excessive sweating—it is time to pull the plug on the race and seek immediate medical care. 

Dr. Krebs, the internal medicine doctor, agrees that GI distress is often one of the first signs of bigger issues in the body, and should be paid attention to even before the race.

“I’ve seen athletes who have had the flu or a stomach bug a few days before a race and thought they’d be fine to compete because they chugged some Gatorade before the race,” Dr. Krebs says. “I advise athletes not to toe the line in that situation because you’d be starting the race at a deficit. In my opinion, a DNS [Did Not Start] is much less heartbreaking than a DNF.”

For those who do make it to the start line in a healthy state, Dr. Krebs notes that monitoring heart rate can be a good indication of if the body is responding normally to race day stimuli. 

“If you are racing at an intensity you are used to and your heart rate is way off, you need to pay attention,” Dr. Krebs says. “If your heart rate goes way up during moderate exercise, that’s an early sign of dehydration.” 

A high heart rate combined with nausea, vomiting, and diarrhea are all signs to “pause and reassess,” as Dr. Krebs says. 

Dr. Krebs echoes Dr. Vanos in that endurance athletes have a responsibility to assess their bodies and know if physical symptoms are out of the ordinary. If an athlete is experiencing an abnormal heart rate and extreme GI distress, it is unlikely for an athlete to recover during the race, and the athlete should DNF. Dr. Krebs recommends that if any bone or joint experiences intense trauma during a race, it’s best to DNF, as well. 

“If you hear a pop or have extreme pain in a joint or bone, that’s a hard stop,” Dr. Krebs says. “You do not want to risk trying to race on a fractured or broken bone.” 

To prevent the onset of GI distress, practice a nutrition and hydration plan that sits well with your body and provides you with the needed electrolytes, fluid, and calorie profile to carry you across many miles. Wearing a heart rate monitor can help you keep an eye on dehydration and exertion levels, as Dr. Krebs explains.

Incorporating strength and agility work into your training will make joints, muscles, and tendons more resilient to the errant trip or fall on race day, and may help guard against sprains, fractures, and bone breaks. 

There will always be another race day, which is important to remember when dealing with mental or physical distress. We only get one body and one mind, so treating them well as we traverse through training and competing is the ultimate victory. 

Be sure to listen to race day medical personnel and consult with your doctor before beginning a training regimen or entering an endurance event.

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