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Train Your Gut and Prevent GI Issues on Race Day

By Stevie Smith | May 21, 2018, 6:44 p.m. (ET)

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You set a goal, make a plan and put in the work for your “A” race. You show up to the start line well rested from tapering and ready to go after all the sacrifices you made in training. And then it happens, that “uh-oh” moment where you’re looking for the nearest port-a-potty or in the most desperate situations, bushes.

What causes this GI distress? It can be a number of things. For most athletes, the reasons include hydration status, concentration of fluids consumed, exercise fuel choice and exercise intensity. So what happens to your body during exercise that puts athletes at an increased risk of GI issues? During strenuous exercise, blood volume is prioritized to your working muscles and skin to provide oxygen, energy and to relieve heat through sweat. Because your body is working hard to do these functions, less energy is spent digesting the nutrition you take in during your race. The higher the intensity of your workout or race, the more blood is taken away from the work in your gut to help your quads, hamstrings and glutes get you across that finish line.

One of the culprits of these unexpected belly issues is when an athlete allows dehydration to set in. When we allow ourselves to become dehydrated, gastric emptying is delayed and as a result this potentially leads to nausea, vomiting and abdominal pain. Often athletes wait to drink fluids until they feel thirsty, which at this point is too late as dehydration has already begun and therefore athletic performance is compromised. In addition to dehydration already beginning, when you wait until you feel thirsty to take in fluids on the race course, the tendency is to guzzle them down in much larger quantities than if appropriately paced throughout the race. This large amount of fluid chugged will in turn lead to some extra pit stops along the race course as once dehydration sets in, it results in a delay of gastric emptying of all the fuels in our stomach causing that unwelcomed GI distress.

During training, you want to also ‘train your gut’ to be able to take in enough fluids on race day without causing distress. The best approach to prevent this is by sipping fluids throughout or small quantities about every 20 minutes. The sugar source in your sports drink can also bring about those ‘uh-oh’ moments that leave you looking for the nearest bush. It’s been shown that athletes consuming sports drinks with multiple sources of carbohydrates for example, fructose and maltodextrin, have fewer reported GI issues than those athletes who use a beverage with a single source of carbohydrate.

What should you do if GI issues strike during racing? Slow down! This may seem counterintuitive since it is a race after all, but by doing so it slows your heart rate down and you begin to allow your body to send more blood to the gut for increased digestion. Keep taking sips of water until your stomach settles and be on the lookout for the nearest port-a-potty.

Use of NSAIDs (non-steroidal anti-inflammatory drugs), such as ibuprofen, can also lead to GI issues on race day or in training. Many athletes use these to relieve pain or in anticipation of pain during the race. It’s been shown that these drugs increase gut permeability and increase the risk of complications such as GI bleeding and perforation. NSAIDs should be avoided on race day and leading into race day to prevent issues. This is even more important for athletes with a history of gastrointestinal issues.

How can you prevent GI distress? Have a plan! Try out the nutrition and hydration you plan to use on race day during training. Here you can figure out what products you can tolerate on race day. Nutrition is very individual, so what may work for your friend or training buddy may not work for you. It’s crucial for you to figure out what different sport foods and drinks work for you to avoid any GI mishaps on race day. Be sure to also practice your race nutrition at race intensity to ensure tolerance as a part of training the gut. If you want to be able to take what’s provided on the course, be sure to see what the race you are competing in offers, as it tends to vary from race to race, and start training with it!

“By far, the biggest mistake athletes make in terms of GI distress and handling their race fueling, is the lack of fueling practice. It is critical to practice race fueling at or above quantities required for race day year-round and during every single training session,” said Jesse Kropelnicki, QT2 systems founder, pro coach and USA Triathlon Level III Certified Coach. “Most athletes step up their race fueling from what is practiced in training under higher stress, heat and intensity and expect it to all just magically work out! Over-practice race fueling the final 10 days before race day, step it down, and make space to add the other stressors instead.”

Other ways to prevent unwanted potty stops include avoiding sugar alcohols like sorbitol (which can have a laxative effect) and sticking with familiar foods and sports drinks on race day. After all the time-spent training for your race, don’t let your approach to race day nutrition limit you!

Stevie Lyn Smith RD works as a part of the team of registered dietitians at The Core Diet, working with IRONMAN and other endurance athletes. She is currently working on her M.S. in applied nutrition with a sports and fitness concentration through Northeastern University and holds her B.S. in dietetics and nutrition from Buffalo State College. She is also an avid athlete herself having completed seven IRONMAN-distance triathlons, 19 marathons, and one 50-mile ultra-marathon among many other types of races including long-distance swimming. She believes that optimal nutrition can not only improve performance and recovery but also improve quality of life. You can contact her via email at

The views expressed in this article are the opinion of the author and not necessarily the practices of USA Triathlon. Before starting any new diet or exercise program, you should check with your physician and/or coach.