Do You Get The 💩 Racing?


WHY DO GUT ISSUES OCCUR? (0:00 - 11:52)

WHAT CAN YOU DO ABOUT THEM? (05:06- 12:23)

TRAINING THE GUT - WHAT IS IT? (12.23-21:59)

TRAINING THE GUT - HOW? (22:00-34:40)

PRO EXAMPLE (34:40-37:50)

KEY TAKEAWAYS (37:50-40:22)

Q&A (40:23-1:04)


At first I’d do my runs with a lot of discomfort. But I kept doing this in my longer workouts, especially longer brick sessions. I would finish my ride and then get more food in before going out for my run. I was doing one to two run sessions a week with a lot of pressure in my stomach!” Eneko Llanos, Pro Triathlete


“You can use solid foods in training and then transition to gels and drinks on race day. Because again that's going to make race day easier.  If you can tolerate that volume in training , that'll make it even easier (on race day).”
Dr Alan McCubbin


Eneko LLanos Burguera (2008 Kona Runner-Up) had a long history of gut issues whilst racing. he searched the world looking for answers. Thankfully he managed to sort it out. The solution to his gut issues was training his gut. This was after all other GI elements were eliminated. It is possible to improve GI complaints in racing. You just need to be methodical.


There's not a one-size-fits-all solution to solving gut issues. It is a complicated topic and one that often requires the assistance of an expert. This often saves a lot of time on the athletes behalf. Here are the three main reasons that gut issues present to an athlete

A. Lack Of Blood Flow To The Gut
Firstly during exercise there's a lack of blood flow to the gut. This can be worse in certain situations. Risk factors include medications such as NSAIDs and lack of nutrients in the gut. Particularly in hot weather that's more so the case because you get more of your blood flow going to the skin rather than to the gut in high intensity exercise. As a result you get more blood flowing to the muscles rather than the gut. If you have a lack of nutrients (food) because you don't consume anything other than water then this doesn't stimulate some of that blood flow to return to the gut. Whereas having some nutrition in your gut will actually stimulate some of that blood flow in the gut and assist. The lack of blood flow can cause damage to the lining of the gut. This can cause issues with the tight junctions of the gut lining and in the worse case scenario leads to endotoxemia.

B. Increased "Stress Response" To Exercise
The most common issue. What we call the stress response to exercise. Exercise is  a form of stress whether we think about it like that or not and that can have a couple of different components to it. It can be the physical stress of exercise, like the intensity of exercise. Higher intensity tends to increase the stress response. Higher body temperature tends to increase the stress response. Dehydration tends to increase the stress response. Some new research has highlighted stress response at night time is worse than daytime. For Ultra marathons this is relevant where the athletes are going overnight.  More recently, psychological stress and the impact anxiety and race day nerves have on stress response to exercise has been researched. Basically what happens is the typical kind of fight or flight response that you get is an increase in one of the parts of your nervous system that you don't consciously control. Basically it slows down the function of the gut so that stomach slows down the emptying rate or some some cases if it's extreme stops altogether. The intestines stop moving food through and and the system basically just kind of shuts down. So, you get a lot of reflux nausea ,vomiting, cramping and pain. In some cases you get the nutrients just not being digested and absorbed properly and it passes through eventually into the large intestine

C. Presence of "fermentable Stuff" From Food In The Gut
Very technical yet very appropriate to describe what can happen. The presence of fermentable stuff from food in the gut. This can be fiber, it can be what we call FODMAPs -which is a bunch of different starches and sugars that humans generally don't digest and absorb very well or at all. In some cases it can also be normal carbs that you should be able to digest and absorb easily but because of the first two issues not being digested and absorbed easily. You can also see this sometimes in athletes that have been following a very low carbohydrate diet for a long time and then decide to have 90 grams an hour of carbs in their race. Their body just doesn't have the mechanisms in the gut wall to digest and absorb that amount of carbs because it's been adapted to a low carb diet. In that situation the same thing can happen so basically in this situation you get all of this fermentable stuff, fiber, FODMAPs and other types of carbohydrates usually entering the large intestine. This does a couple of things - one it sends feedback back to the stomach and says "hang on, stuff's getting to the end unabsorbed! Slow down " In this case, food is going through too quickly and so that slows down all the movement of everything remainging and already present through your gut.  This causes the gut issues when exercising. The second thing that happens is the bacteria in your large intestine chew up all that "fermentable stuff". That's the fermentation part of it. The bacteria produce gas as a side effect, draw water into the gut and gives you a lot of more lower gastrointestinal issues. Flatulence (farting) adn diarrhea as well bloating, wind, and cramping.

A few other factors that can contribute to GI issues during exercise.  Some athletes have generally poor digestion and absorption of carbs. Typically seen in athletes who have been on low carb diets for a long period of time. This is porposed to be due to changes in the gut taht relate to the transporters of carbohydrates and limited numbers.

Other athletes can have generally a poor tolerance of food and fluids. For example, your stomach is not very good at stretching to accommodate the volume of food and fluids that you're consuming. The extreme example of someone who's very well adapted would be those people who do Major League eating. They can eat  70 hot dogs in 10 minutes. They have a stomach that's very adapted to be able to stretch and accommodate that amount of food without it coming back up again. Thisshows how the stomach and gut is trainable. It is trainable. You can train your stomach to stretch - that's a big part of gut training.

The final part is the mechanical side of things. This is still a little bit controversial. A lot of people report that gut issues are worse in running compared to cycling. However, it's still a bit of a chicken and egg scenario. Is it the act of running ? The mechanics of going up and down making things worse? Is it simply that when people are running or pure runners - they are  less gut trained because they tend to be taking less carbs and fluid with them when they run. The same may be true for triathletes doing their run sessions without a lot of fuel as opposed to their bike sessions. This is the thought process of whether it's the mechanical issue or whether it's just less gut training specific to running. Whichever one causes the issues, we don't exactly know. The question is obviously what do we do about all these sort of gut issues that can occur!


Scott was on  SWEAT ELITE podcast with Matt Fox.

Elizabeth featured in IRONMAN with a delicious Finnish recipe

IRONMAN featured Fuelin in an article about Holly Lawrence

Scott wrote an article for IRONMAN on Sweat Rate

Scott Tindal
May 6, 2024
Back to all articles