How to Train your Gut for Race day Performance

You spent weeks and months training your heart lungs and muscles but not training your gut could be leaving you short on race day! Getting your fuelling right is absolutely crucial to having a successful race day. In triathlon for example we often hear nutrition referred to as the 4th discipline; it has now become an arms race in who can translate their nutrition into the best performances on race day. With the ever-increasing evidence supporting the need to fuel well during racing, how we train our guts to tolerate what we eat and drink during races has now become crucial in optimising our individual performances and making sure that we have a great race.
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We've all been there halfway through a race and we started to feel symptoms like heartburn, uncomfortable bloating and really, really needing the toilet! These are the most common symptoms of gastrointestinal (GI) distress during triathletes in races – research has shown that in an average race at least 40% of people get GI issues. There are a whole host of reasons why this can happen and unfortunately it can be quite individual as to why. Research has shown that it is dependent on factors such as genetics, biomechanics, anatomy, age and training status, with each individual response often being circumstantial. Hot conditions, intensity and potentially dehydration or poor nutrition can all make gastrointestinal issues during races.
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Considering all these factors, training your gut is absolutely an essential part of the training process. Just like your heart lungs and muscles we can train our gut to be ready and optimised for race day. Here we're going to dig into the research behind how much to fuel on race day, how to train your gut, how long it should take, and look at some practical ways to train our gastrointestinal systems to be race day ready.

What does training the gut actually mean?

Training the gut refers to optimising the way our digestive system absorbs carbohydrates whilst we're doing exercise at race intensity combined with ingesting the types of drinks, gels and sports foods that we're going to use during the race.
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In the same way that our muscles get fitter and stronger by training we can also train our digestive system particularly our intestines to absorb more carbohydrate during exercise. The digestive system is a pretty amazing set of organs and very trainable, for example the internal lining of our intestine renews itself about every five days which means as an organ it's incredibly adaptable and very responsive to training stimulus.

How much carbohydrate should I take on during a race?

Every athlete has a unique requirement, but if you're new to racing then a good benchmark target is 60 grams of carbohydrate for every hour that you're competing. If you're a little more experienced 75 to 90 grams of carbohydrate per hour is a good target to go for, and if you're very experienced you could look at up to 120 grams per hour.

How should I fuel my races?

If 60 grams per hour is your target, you should combine carbohydrates, drinks, and sports foods to achieve a total of 60 grams of carbohydrates per hour. You can use any form of carbohydrates that you like, and it's best to try a few brands and different foods to see which your body responds best to.
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If 75 to 90 grams of carbohydrate is your target it's going to be important that you use a mixture of glucose and fructose sources of carbohydrate, again getting these from a mixture of drinks solids and gels. It’s important to find sports foods and sports drinks that have a mixture of glucose and fructose, quite often the high carbohydrate drinks that have 80 grammes of carbohydrate, in a 500-millilitre solution, will have a mix of dual source sugars i.e. Glucose and fructose in them. The reason we need glucose and fructose is that the intestinal transport proteins that carry glucose across the gut membrane into the blood, become saturated at approximately 60 grams of glucose per hour. Whereas the transport proteins for fructose are different and so we're able to transport more carbohydrate across our gut membrane when we use multiple types of sugars. This has been one of the one of the biggest steps forward in race fuelling in the last decade.
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If you're an extremely experienced athlete racing at a high level and you're going to move towards 120 grams of carbohydrate per hour it's advisable to use specialist sports nutrition products, again using a mix of glucose and fructose delivered through fluids, gels and sports foods. It’s also worth getting the advice of a sports nutrition specialist or sports dietitian.

Which products should I use?

Once you've established how much carbohydrate you want to take on per hour during your race its important you find a brand of drinks, gels, bars etc. that works for you. Once you know your brand its vital you practise with these products in training. A big mistake that people often make is using one brand of drink, gel, or bar during training and then a different one during race, because the products given out at the race are completely different. This can cause big stomach problems! By practising with the specific brands, the specific drinks, gels, and bars that you want to use on race day you not only train your gut, but how and when to eat and drink becomes almost automatic. You know how much to drink and when to have that gel because you've done it in training. It's important to remember that the biomechanics of running and cycling on our stomach and digestive tract are very different, so a product that works well for you on a bike might not work that well for you on a run.

When should I begin training my gut?

You can begin to train you gut anywhere from 6 to 10 weeks before your race, the more you practise the better the adaptation and the more automatic your in-race fuelling becomes. Just like training your cardiovascular system a good approach is to begin light and build up. If your target is 60 grams of carbohydrate per hour, start by beginning to fuel with 20 or 30 grams of carbohydrate per hour during at least two training sessions per week – longer endurance, low intensity training sessions are best. Use 20 – 30 grammes for two weeks before increasing it to 40 grams for 2 weeks and subsequently increasing it to 60 grammes for the final 2 weeks before a taper. If you're going to be racing in hot conditions, it's a good idea to take on at least 50% of your carbohydrates from fluids as this will also help to keep you hydrated.

Building nutrition in as part of your training routine more generally will also help with training your gut. Having more energy and carbs on harder training days and less on easier days is recommended, you can use apps like Hexis to align your nutrition with your training to optimise your adaptation.

During the early phases of training you might feel a little bit of discomfort during training but don't worry there's nothing to panic about this is a normal response of your body. It's important to listen to your body and if it becomes too uncomfortable then ease back and don't try to force more carbohydrate into your system, do a few more sessions at a comfortable rate before slightly increasing again. It’s ok to have some discomfort in training, but you really wouldn’t want it on race day!

Don’t forget race day breakfast!

he last thing that most people forget about is the timing of breakfast on race day. Depending on the race you might have a very early start, if you race starts at 6 or 7am you will need to have finished breakfast by 4.30 or 5am at the latest. Most people don’t eat that early and so when we do it can cause GI issues. In the same way you’d practise how you’re going to fuel during the race its also a good idea to practise what and when you’re going to eat before the race.

Tick these boxes in the weeks leading up to a race and you’ll significantly reduce the risk of getting any GI issues, you’ll be well fuelled and give yourself a great shot at a good performance.

Summary:

Carb Intake Goals: 60g (beginners), 75-90g (intermediate), 120g (advanced).

Carb Sources: Mix of drinks, gels, sports foods; 60g+ glucose + fructose for better absorption.

Consistency: Use the same products in training and racing.

Training Schedule: Start 6-10 weeks prior, gradually increase carb intake.

Manage Discomfort: Increase carbs slowly, listen to your body.

Pre-Race Meal: Practise early breakfast timing.

Carbohydrate Intake Targets:

Beginners: Aim for 60 grams of carbohydrates per hour.
Intermediate: Target 75 to 90 grams per hour, using a mix of glucose and fructose.
Advanced: Up to 120 grams per hour, ideally with specialist sports nutrition products and professional advice.

Carbohydrate Sources:

60 grams/hour: Use a combination of carbohydrate drinks and sports foods. Experiment to find what suits you best.
75 to 90 grams/hour: Use a mix of glucose and fructose. Look for products with dual-source sugars, like high-carb drinks containing 80 grams of carbs per 500 ml. This is because glucose transporters in the gut saturate at around 60 grams per hour, while fructose transporters allow additional absorption.
120 grams/hour: Use specialised products with glucose and fructose and consult a sports nutritionist.

Consistency and Practice:

Choose a brand of drinks, gels, and bars that work for you and stick with it during training and racing to avoid stomach problems.
Practice using these products in training, simulating race conditions. This helps your gut adapt and makes your fuelling strategy automatic on race day.
Different products might work better for cycling versus running, so test accordingly.

Training Timeline:

Start training your gut 6-10 weeks before the race.
Begin with 20-30 grams of carbs per hour during long, low-intensity sessions. Gradually increase the intake every two weeks: 40 grams, then 60 grams.
For races in hot conditions, ensure at least 50% of your carbs come from fluids for hydration.

Dealing with Discomfort:

Some discomfort is normal initially. Listen to your body and increase carb intake gradually. Avoid forcing carbs if discomfort is high.

Pre-Race Breakfast:

Practice eating an early breakfast similar to race day. For early starts, finish breakfast by 4:30 or 5 AM to avoid GI issues.

By following these steps, you'll reduce the risk of gastrointestinal problems, ensure adequate fuelling, and enhance your performance on race day.

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Fuelling is the difference between good and great, ordinary and extraordinary. It’s essential for maximising workouts, effective recovery, and achieving your true potential.

Every athlete is unique. That’s why we developed Hexis—an intelligent, personalised fuelling plan that adapts to your needs. Built on advanced nutrition technology, Hexis is proven to improve your performance. Learn more and take your performance from good to extraordinary.

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