nutritional challenge

Nutritional Challenges in Ultrarunning and How to Overcome Them

By Jason Koop,
Head Coach of CTS Ultrarunning

One of the things I love about coaching ultramarathon athletes is adapting the standard recommendations and best practices from the coaching industry into an ultra-specific context. All too often, the recommendations we see aren’t geared for us. They are geared for the weekend 5k crowd, the gym goers and runners who see aid stations every mile.

Take the ‘drink to thirst vs drink on a schedule’ argument that continually makes the rounds. What you will see in the popular literature goes something like this: ‘during exercise thirst is the only mechanism you need to signal you to drink’. Anyone who believes that statement has not run through Death Valley in the middle of summer, where the sun radiates off of the pavement and literally sunburns the roof of your mouth, thereby ruining your seemingly perfect thirst mechanism. I can come up with dozens more examples where this is similarly true for ultramarathoners. The fact of the matter is that ultrarunning presents many unique nutritional challenges that athletes need to prepare for in training so they can overcome them on race day.

Length of the event

Challenge: The simple fact of being outdoors, awake, and on your feet for many, many hours creates a nutritional challenge. Athletes in shorter events can eat a pre-race meal, and relatively easily consume calories and fluid to support their energy expenditure and thermoregulation needs. And then, they finish their event before needing another meal. Utramarathon athletes are not so lucky, and the problem can get trickier – or sometimes easier – as the race distance gets longer.

Adaptation. Train your gut! Ultramarathon runners must develop the ability to consume and digest a steady stream of calories over the course of many hours. This does not happen passively. Training the muscles in your gut is very similar to training the muscles in your legs and heart. Given a stress and then rest, they will adapt to better tackle the task at hand. All too often athletes go into their ‘race day’ nutrition plan without rehearsing it beforehand in training. I encourage my athletes to go through their race day plan 4-6 times in training during the build up for a longer event. This not only allows the race day plan to be more natural, reducing the mental input necessary (see section below), but also trains the gut to digest and absorb the calories required.

Long Distances/Times Between Aid Stations

Challenge: Did you know that the Chicago Marathon will use over one million paper cups on race day every year (1)? This adds some context to the next cupless race you enter. As opposed to picking up and throwing away those green paper cups every single mile, ultramarathon athletes have to carry stuff from aid to aid station. Sometimes that gear is mandatory. The added weight puts additional strain and stress on the musculoskeletal system. It is also an opportunity; you can eat and drink whatever you want, whenever you want.

Adaptation: Pretty simple, train with the gear (pack, bottles, bladder, etc.) you will use on race day. Sure, you don’t need 5 gels, 2 bars and 3 bottles for a 2-hour run. But, if you are going to need 5 gels, 2 bars and 3 bottles to get from Ouray to Telluride on the Hardrock course, you sure better get used to carrying it in training.

Dramatic Changes in Environmental Conditions

Challenge: Anyone who has run the Leadville Trail 100 is familiar with their ridiculously early 4 AM shotgun blast to mark the start of the race. Aside from setting your alarm clock at a time it’s never seen before, the early morning environment creates additional challenges. At 10,000 feet above sea level, the crisp mountain air at the start line can be brutally cold. Temperatures can be near or below freezing. As the day progresses, you can find yourself running along the Colorado Trail with temperatures in the 80’s, almost as if you are on another planet. These changes greatly impact your sweat rate and your perceptions of hunger and thirst.

Adaptation: Know your calorie and hydration needs for different conditions. Your calorie needs will be relatively static, your hydration needs are not and increase as the temperature increases. Fortunately, most ultramarathon athletes train year-round so they can get a feel for their hydration needs in different conditions. Performing the ‘sweat test’ in different conditions (50, 60, 80 degrees) is a great way to get a gauge on how your body reacts in different temperatures. Keep in mind, your body will adapt (generally sweat more) as you become more trained and more exposed to hotter temperatures.

The Sweat Test

  1. Weigh yourself nude right before a run.
  2. Go do a one hour run at EnduranceRun intensity.
  3. After the run, strip down, wipe down any sweat, and weigh yourself nude again.
  4. Subtract your end weight from your beginning weight. Convert the weight to ounces (one pound equals 16 ounces). This is your hourly sweat rate in those specific conditions.
  5. Aim to replace ~90-95% (not 100%) of those fluids. Why not 100%? Because in an ultra, weight loss from water stored in fat and carbohydrate are significant and does not need to be replaced. Replacing 100% of the sweat loss in an ultra can lead to hyponatremia, or low blood sodium.
  6. Repeat the test in different conditions. I recommend using 10 degree Fahrenheit differences.

General Fatigue and Diminished Decision-Making Ability

Challenge: Thinking costs time and energy. In study after study, subjects exerting brain power before or during activity have their physiology and performance suffer (2,3,4). To compound this, ultramarathons are really hard (news flash). And to compound this even further, there are a lot of decisions to be made during an ultra (do I eat, slow down, am I following the pink markers or the yellow markers, etc.). These conditions conspire against you and ultimately hamper your performance directly (see studies above) or indirectly by way of mistakes. How many times have you seen a runner leave an aid station without refilling a hydration pack or zone out and not consume anything for miles? These errors result from cumulative fatigue managing multiple decision inputs, not simply forgetting.

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Adaptation: The more simple and automatic any of your race day routines are, the more effective they will be. Habits that are consistent from everyday training sessions to your longest races should become ingrained to the point you stick to them even when you are unbelievably fatigued. Have a routine you use every time you pick up your hydration pack: Check for fluid, food, and equipment (like a rain shell or poles). Keep things simple. If you are fretting about packing or forgoing your 3 oz rain shell for the last 8 miles, you’ve already burned enough mental energy to more than compensate for the minuscule amount of weight difference.

Free Ultrarunning Training Assessment Quiz

Take our free 2-minute quiz to discover how effective your training is and get recommendations for how you can improve.

Food and Flavor Fatigue

Consuming small amounts of similar food and fluids over and over again during the course of many hours is physically exhausting as well as tiring to your taste buds. This is rarely a problem in shorter events because less food is needed to complete the race. You can have 5 gels of the exact same flavor if 5 is all you need. When you need the equivalent of 25 gels, eating all vanilla – or all gels – might not cut it.

Athletes competing in shorter events can utilize a narrower range of food options, whereas ultradistance athletes typically need to find a wider range of foods they are willing to eat and that work for them without causing stomach upset. I have spent so much time working through the challenge of food fatigue with athletes that I have developed a specific strategy to deal with it, which I call The Bullseye Nutrition Strategy.

Stay tuned for next week’s blog post on all the details of the Bullseye Nutrition Strategy and how to make it work for you.


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  2. Slimani, Maamer & Znazen, Hela & Bragazzi, Nicola & Sami Zguira, Mohamed & Tod, David. (2018). The Effect of Mental Fatigue on Cognitive and Aerobic Performance in Adolescent Active Endurance Athletes: Insights from a Randomized Counterbalanced, Cross-Over Trial. Journal of Clinical Medicine. 7. 10.3390/jcm7120510.
  3. Martin, Kristy & Meeusen, Romain & Thompson, Kevin & Keegan, Richard & Rattray, Ben. (2018). Mental Fatigue Impairs Endurance Performance: A Physiological Explanation. Sports Medicine. 48. 10.1007/s40279-018-0946-9.
  4. Marcora SM, Staiano W, Manning V. Mental fatigue impairs physical performance in humans. J Appl Physiol. 2009;106(3):857–64.

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Comments 3

  1. Pingback: What Training Data is Worth Tracking for Ultrarunners? - Jason Koop

  2. Pingback: Bullseye Nutrition Plan for Ultramarathon Runners - Jason Koop

  3. Re: the picture at the top of the article, that lady is eating my favorite anti-bonk food – Little Debbie Oatmeal Creme Sandwich! 🙂

    I have far less experience and expertise than Jason, but have found the same thing about eating the same thing over a long time (in my case, on a bike). Sometimes the most nutritionally appropriate food makes you want to barf just looking at it. When that happens, anything you can get down your throat is better than nothing.

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