Get access to everything we publish when you sign up for Outside+.
The list of issues and injuries that an ultrarunner can face while racing is lengthy. Blisters, chafing, cramps, muscle strains, knee pain, heat illnesses, and altitude sickness are just a handful of the possibilities. Perhaps none of these potential problems, however, are as prevalent and impactful during ultramarathons as nausea and vomiting. Indeed, practically every ultrarunner has their own tale of yakking on the side of a trail or into an aid station trashcan. For some, it’s an unlucky one-off event, but for others, recurrent nausea consistently mars their ability to perform up to their expectations.
The reason so many ultrarunners get stricken with nausea is undoubtedly multi-faceted, and to be honest, there is not a cut-and-dry singular explanation. Still, we do have some clues as to why the prevalence of nausea and vomiting is up to 2-3 times more common in these races than much shorter distances. Let’s take a look at what the research says about the possible culprits as well as some of the strategies you can try to deal with this troublesome symptom.
Just How Common Is Nausea?
Beyond the anecdotes, what exactly do we know about the prevalence of nausea in ultrarunners? Before we get to some data on that question, it’s important to recognize that surveys used to gather this information quantify nausea differently. In addition, the occurrence of nausea is likely to vary with temperature and humidity, elevation, and the length of a race. As such, it’s a bit foolhardy to throw out a single estimate of nausea and think that it applies to every ultrarunning scenario.
Caveats aside, some of the relevant data tells us that nausea incidence clearly increases with race duration. Dr. Martin Hoffman, professor emeritus in the Department of Physical Medicine and Rehabilitation at the University of California, Davis, has overseen several studies on this topic, and in some cases, up to 6 out of 10 runners experience nausea during an ultramarathon. To give you some perspective, consider that around 10% of regular marathoners typically suffer from nausea.
Now, some of these cases of nausea are quite mild or transient, meaning they won’t hurt performance much. Still, up to half of cases can be severe enough to impact ultrarunning performance. In fact, one of Hoffman’s investigations found that nausea or vomiting was the leading reason for racers to drop out of the Western States 100-mile Endurance Run. During a regular 26.2-mile marathon, a runner suffering from nausea near the end of the race is likely to grit their teeth and finish. In contrast, the thought of having to suffer for another 20, 30, or 50-plus miles while feeling queasy is, very understandably, too much for some ultrarunners to cope with.
The puzzle of why nausea is so common during ultrarunning is difficult to solve, in large part because there are multiple physiological changes occurring simultaneously over the course of an ultrarace. It’s also incredibly tough to match the demands of an ultrarace in a laboratory, so mechanistic studies looking at the origins of nausea during super-prolonged exercise are few and far between.
Even with the scientific uncertainty, we do have some decent guesses as to what’s provoking the urge to spew in so many ultrarunners. During prolonged exercise, you secrete hormones like adrenaline and glucagon into your blood that allow your body to liberate fat stores, make glucose, and maintain your blood sugar levels. Arginine vasopressin, a fluid-conserving hormone, is also released so that you can reduce urine production. Blood levels of endotoxins (sort of invader molecules that seep through your gut’s walls) and inflammatory molecules can also surge. And finally, you’ve got muscle breakdown products, like urea and creatine kinase, spilling into your bloodstream. All these substances can stimulate what’s called the chemoreceptor trigger zone in your brainstem, which communicates with another brain region called the vomiting center.
Long story short, you’ve got a cocktail of substances circulating in your bloodstream that act as a potent trigger for nausea. The concentrations of all these substances tend to increase over time during prolonged exercise, which may help to explain why nausea becomes much more common in the latter half of ultraraces.
A Nervous Gut
The release of stress hormones like adrenaline can also occur even before you take your first official stride during an ultra. Throughout the history of sport, many athletes have been plagued by precompetition anxiety severe enough to induce vomiting. Bill Russell, perhaps the best center of all-time in the sport of basketball, reportedly vomited before many of his big games. There’s also a moment in the Steve Prefontaine biopic Without Limits that perfectly captures what prerace nerves can do to even the most elite athletes. In the scene, Prefontaine is seen puking under the grandstands before his race against other running greats like Frank Shorter and Gerry Lindgren, even as the crowd chants his name.
These anecdotal accounts are also beginning to be backed by research. Just this year, two of my colleagues and I published an investigation that found anxiety to be associated with the occurrence of nausea in endurance race competitors. The study, published in the European Journal of Sport Science, had 186 endurance-trained individuals document their life stress and anxiety as well as the gut symptoms they experienced during one of their recent races. A subset of the subjects also reported how anxious they felt on race morning. Ultimately, racers who reported higher levels of general anxiety had over three times the odds of experiencing significant levels of nausea during competition. Further, those who reported lots of anxiety on race morning had over five times the odds of experiencing substantial in-race nausea.
These are correlations, so it’s hard to definitively prove that these athletes’ nausea issues were completely due to anxiety. That said, other lines of evidence support the idea that this relationship is at least partially cause and effect. Plus, most of us have had our own out-of-sport run-ins with gut distress stemming from worries and anxieties, whether they be from a first date, a medical procedure, or an interview.
Sweltering Heat and Altitude
Environmental conditions also play a major role in development of nausea during ultras. Some of the most prominent ultramarathons in the world (e.g., Western States Endurance Run, Badwater Ultramarathon, Marathon des Sables) are held in sweltry conditions. When researchers ask runners to exercise in the heat, the incidence of nausea can quadruple in comparison to exercise carried out at the same intensity in more mild conditions.
Besides the heat, another environmental factor that many ultrarunners deal with is altitude. Nausea is a well-known symptom of acute mountain sickness, with written accounts going back at least several hundred years. Add exercise to the mix, and you can start to understand why nausea is a big issue for competitors at races like the Hardrock 100 and the Khardung La Challenge, which has the highest elevation of any ultrarace in the world.
Fueling: A Delicate Balance
One other notable contributing factor to nausea is in-race fueling. The nutritional demands of ultrarunners can far outpace those of other athletes competing at shorter distances. For those ultrarunners who are looking to push the boundaries of what their bodies can do, they might end up consuming carbohydrate at rates of 60-90 grams per hour. That’s roughly equivalent to 3-4 sport gels per hour! Even lesser amounts of carbohydrate (30-60 grams per hour), though, can pose a significant challenge to the gut’s capacity to digest and absorb fueling.
In short, fueling during an ultramarathon often takes place on a knife’s edge. Too little can lead to a bonk and even nausea if your blood sugar gets too low, while too much foodstuff can also provoke the gut and induce queasiness. With that in mind, it’s critical that ultrarunners practice their fueling strategies multiple times throughout the weeks leading up to a race. Ideally, at least some of these gut-training sessions would be done at a pace similar to race-pace and in similar environmental conditions that an athlete expects to compete in.
Strategies to Quell or Avoid Nausea
Given all this information, you might be wondering how to best avoid the nauseous fate of so many ultrarunners. First, you should accept the fact that there is likely no ironclad way to completely eliminate the risk of nausea during an ultra. There are just too many potential causes. That being said, you do have the power to minimize your risk of being stricken with severe nausea. And for some athletes, it will be important to take a multi-pronged approach as opposed to relying on a single strategy. Below are my top five tips for reducing the odds of tossing your cookies during your next ultra.
- Acclimate to the heat and altitude if your race is held under those conditions. Likewise, employ cooling strategies (e.g., drinking cool beverages, putting some ice in your cap or shirt, dousing yourself with cool/cold water, etc.) throughout a race that’s held in sweltering conditions.
- If you suffer from prerace nerves, try techniques like slow deep breathing or mindfulness. Better yet, consult with a sports psychologist.
- Avoid both overhydrating as well as underhydrating. During a single-stage ultramarathon, some amount of weight loss is normal (due to the loss of energy stores), so you shouldn’t be drinking so much that you weigh the same or more after a race as before the race. On the other hand, large body mass losses (e.g., >5%) may be a sign that you’re underhydrating.
- Train your gut! If you plan to push the boundaries of food and fluid intake during the race, of course it makes sense that you should practice your nutrition plan during some of your longer training runs. Much like other organs in your body, the gut is adaptable.
- Try ginger. I’m generally not a purveyor of supplements, but if the above mentioned strategies don’t do the trick for you, there is at least one nutritional product that has shown some anti-nausea properties in settings outside of exercise: ginger. To be specific, these anti-queasiness effects have been most often studied in nausea occurring during pregnancy, motion sickness, and chemotherapy. No supplement is without risk, and many products sold in the U.S. are of questionable quality, so anyone looking to use ginger supplements—or any other supplement for that matter—should do their research and consult with their healthcare provider as well.