How to avoid digestive problems in trail running and cycling

If you've ever had to stop mid-climb because of your stomach, you know exactly what we're talking about. Digestive issues are one of the most common causes of abandonment in trail running and mountain cycling. And most of the time, the culprit isn't the effort. It's what you're eating during it.

Why the digestive system suffers during exercise

When you're cycling or running at high intensity, your body prioritises blood flow to active muscles. The result is that the digestive system receives up to 80% less blood flow than normal. In that state, processing artificial ingredients, preservatives or highly processed carbohydrates becomes very difficult.

Add the mechanical impact of running or the vibrations of MTB riding, and you have the perfect recipe for bloating, nausea or what runners call the “runner's stomach”: having to stop urgently at the worst possible moment.

The 4 most common mistakes in race nutrition

1. Using maltodextrin gels during long efforts

Maltodextrin is the most common carbohydrate in conventional gels. It has an extremely high glycaemic index, which creates sharp spikes and drops in blood glucose. During efforts lasting more than 2 hours, that energy rollercoaster takes its toll, both on performance and digestion.

The natural alternative: gels based on rice syrup and agave syrup, which offer a more gradual and stable energy release, with much better digestive tolerance.

2. Starting to take gels too late

One of the most frequent mistakes, especially in trail running. Waiting until you feel hungry or bonk is arriving too late: muscle glycogen is already low and recovery is slow and costly. The right approach is to start refuelling before you need it.

General guideline: first gel at 30–45 minutes of effort, then every 45–60 minutes depending on intensity.

3. Taking the gel without water

Concentrated gels need water to dilute and absorb correctly in the small intestine. Without enough hydration, they stay in the stomach longer than necessary and can cause bloating. In mountain cycling this is made worse because hydration tends to be irregular on technical sections.

Practical rule: always accompany the gel with 150–200 ml of water. Avoid combining it with a sugary sports drink at the same time, as the combined sugars can saturate intestinal transporters.

4. Ignoring the ingredient label

Preservatives like potassium sorbate or sodium benzoate, artificial colourings and synthetic flavourings are ingredients that a stressed gut often tolerates poorly. They make a gel work in the lab but can let you down at kilometre 35.

Always read the ingredient list. If you can't pronounce something, your gut probably doesn't know what to do with it either.

Differences between trail running and mountain cycling

Trail running

The constant mechanical impact of running literally shakes the contents of your stomach. That's why more liquid, easy-to-absorb gels work better than denser ones. Texture matters as much as composition.

At long distances (trail marathon, ultra), palate fatigue also comes into play: a gel that tastes great at kilometre 10 can become unbearable at kilometre 50. Variety of flavours isn't a luxury, it's a strategy.

Mountain cycling and road cycling

On a bike, effort is more intermittent: there are descents where energy consumption drops. The challenge is maintaining constant replenishment without overloading the digestive system during high-intensity moments.

In technical MTB, terrain vibrations add mechanical stress to the digestive system. Take your gels on flatter sections or descents rather than mid-climb.

How to choose a gel that won't let you down

• No maltodextrin: choose gels based on natural carbohydrate sources such as rice syrup, agave syrup, dates or real fruit.
• Glucose and fructose combined: a ratio close to 2:1 allows absorption of up to 90g of carbohydrates per hour without saturating intestinal transporters.
• No artificial preservatives: potassium sorbate, sodium benzoate and similar are the first suspects when digestive issues arise.
• Appropriate texture: more liquid for long-distance running; denser is fine in cycling where there is no impact.
• Recognisable ingredients: if you can't pronounce an ingredient, your gut probably doesn't know what to do with it.

How we make PICO gels

PICO was born precisely from this problem. Its creator, a trained chef and cyclist, couldn't find a gel that performed well and whose ingredients he could recognise.

PICO gels keep the list short: rice syrup, agave syrup, pink Himalayan salt and real fruit (or caramel, in the Salted Caramel). The carbohydrate base isn't maltodextrin. No preservatives. No artificial flavourings. Each gel provides 42 to 47 g of carbohydrates and around 300 mg of sodium, with a flavour made to still appeal in the last hour of the race.

Try all 4 flavours with the Tasting Pack →

Nutrition plan for a 3-hour outing

• 15 min before: 1 gel to start with energy.
• Min 45: 1 gel + 200 ml water.
• Min 90: 1 gel + hydration. If the effort is very intense, add electrolytes.
• Min 135: 1 gel + 200 ml water.
• Min 165: last gel to hold your level until the end.

Total: 5 gels for 3 hours of intense effort. Adjust according to your weight, intensity and heat.

Conclusion

Digestive problems during racing are not inevitable. Most of the time they're preventable by choosing better what you carry in your pocket. Your stomach can't tell one brand from another, but it can tell the difference between real food and a chemical formula.