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Top 5 mistakes causing you gut issues on race day

Post by: Gaby VillaNovember 15, 2022

How to stop stomach problems from sabotaging your race

Gut issues are reasonably common among endurance athletes. More than 60% of athletes report gastrointestinal symptoms in longer, ultra-endurance events. Symptoms like nausea, cramping, bloating, side stitches, and frequent toilet stops can negatively impact an athlete’s performance. Avoid these mistakes to minimise your risk of gut distress sabotaging your race. 

Mistake #1 - Not training the gut

Just like your legs, lungs and heart, your gut is trainable. You can train your stomach to tolerate, absorb and digest food more efficiently while moving. 

To achieve this, it is crucial to practice and get used to consuming the same type, quantity and frequency of food you’re planning to eat on race day. It’s not only about trying an energy gel during a run and assuming that eating five will also work. 

Mistake #2 - Not hydrating well

Your gut needs water to assist with nutrient absorption and digestion. By being severely dehydrated, you’re compromising your performance and ability to tolerate food. So it’s no surprise that gut issues tend to exacerbate during races conducted in hot conditions. 

Ensure you drink fluids regularly, especially when eating energy-dense foods like gels or bars.

Mistake #3 - Using the wrong type of carbohydrate 

There are different types of carbohydrates or sugars, each of which your body absorbs differently—some at a slower rate than others. On average, your gut can absorb 1 g of glucose per minute. This is why many nutrition recommendations suggest staying around 60g of carbohydrates per hour so your consumption matches your absorption rate. However, it’s been shown that combining different types of carbohydrates can increase the absorption rate to up to 1.5 g/min. Using a ratio of 2:1 glucose: fructose. Being aware of this, many sports products are now developed using this ratio to enhance gut absorption but not all of them. 

If you have this ratio out of balance and consume more carbohydrates than your gut can absorb, your stomach will likely suffer. 

Mistake #4 - Consuming sodium in inadequate quantities

Besides supporting electrolyte balance and hydration, sodium plays a role in food absorption. However, too little or too much can be distressful for your gut and cause issues on race day. 

Mistake #5 - Eating the wrong food before the event

Fibre and fat are elements you must keep in check in the lead-up to your main event. They both slow gut transit, and eating them too close to the race can mean that your body will still be processing them while trying to go on with your event. 

If you struggle with food allergies or intolerances or still haven’t figured out what is causing your gut upset, I encourage you to seek professional help. Understanding the cause of these issues and implementing a plan to manage them will make your training and race experience more enjoyable. 

The final remarks

You can reduce the likelihood of stomach problems ruining your race. As an endurance athlete, planning and practising your nutrition benefits your performance and reduces the risk of gut issues interfering with your race. 


Burke, Louise, Vicki Deakin, and Michelle Minehan. "Exercise-induced gastrointestinal syndrome, gastrointestinal disorders, food intolerance and allergies." Clinical Sports Nutrition. (2021).

Costa, Ricardo JS, et al. "Gut-training: The impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance.Applied Physiology, Nutrition, and Metabolism 42.5 (2017): 547-557.

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Len Hartley

Previously during Ironman distance events I had issues with hydration and fuelling resulting in a few subpar performances on the run. After speaking to a few other triathletes as well as my coach I decided to contact Gaby at IntensEATfit to get help in identifying and solving these issues to improve my overall performance. While working with Gaby we uncovered that I wasn’t fueling my training sessions well enough, I wasn’t practicing fueling through training enough to condition my stomach to take onboard the required amount of carbs and through testing that my fluid and salt loss was well above average. 

Gaby was great at explaining how these things impact my performance and it was a surprise to find out exactly how much carbohydrate and fluids it takes to successfully fuel and Ironman training & racing. Gaby instilled the importance in training nutrition, and we worked on my nutrition plan weekly allowing my body to get used to the amount of carbs it was taking on board, optimizing the plan to get the best result. This enabled one of the best training blocks I have completed and set me up for a great race in Cairns where I had a strong run to PB by over 10 mins on a challenging course.

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