Why does my stomach only hurt in races, not in training?

Stress, a higher pace and an intake often bigger than in training all stack up. That's why it's worth reproducing your race conditions and intake on long runs.

Should I avoid fibre before a race?

Cutting fibre in the 24-48 h before helps many sensitive runners. It's not mandatory for everyone, but it's worth testing.

Does glucose + fructose really limit trouble?

Above 60 g/h, yes: spreading absorption across two pathways lowers the gut load versus glucose alone. Below that, the difference is smaller.

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How to avoid GI issues during a race

Nausea, stomach cramps, urgent bathroom stops: GI issues are one of the leading causes of DNFs and underperformance in endurance. The good news: they're largely avoidable. The cause is rarely single — poorly chosen products, too high a concentration, too sudden an intake, an untrained gut, stress. This guide walks through the concrete levers for running with a settled stomach.

During: limiting GI trouble

During the effort, three settings make the difference. First, concentration: dilute your drinks enough and take gels with water, never with an already-sweet drink, to avoid an over-concentrated solution in the stomach. Second, regularity: small frequent doses sit better than one big hit. Third, the type of sugar: above 60 g/h, glucose + fructose blends spread the load across absorption pathways and cut the risk of discomfort. Also lower fibre and fat in the hours beforehand.

Before: a meal that sits well

Prevention starts at the last meal. Three to four hours before, favour digestible, low-fibre carbs (white bread, rice, banana), keeping fat, fibre and heavy protein down as they slow digestion. Don't test an unfamiliar food on race day. Pre-race hydration matters too: starting dehydrated worsens GI trouble under effort.

Common mistakes

Taking concentrated gels with a sweet drink instead of water
Swallowing a big carb dose at once instead of small ones
Eating too much fibre or fat the day before and the morning of
Never training your gut for high intakes
Testing a new product on race day

Practical checklist

Well-diluted drinks, gels taken with water
Small regular doses rather than one big hit
Glucose + fructose above 60 g/h
Pre-race meal low in fibre and fat
Repeated high intakes in training (a trained gut)

FAQ

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How to test your nutrition before a race

Race nutrition is tested in training, especially on long sessions and workouts close to race conditions.

Read the guide

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How many carbs per hour when running?

Your carb target depends on the duration, the type of race and what your gut can tolerate.