Endurance Fuelling

Fuelling for marathons, Hyrox and long events

Long events run on carbohydrate. Going in fully fuelled, topping up during, and recovering well can be the difference between a strong finish and hitting the wall. Here is the practical approach for endurance days.

Before: top up the tank

For events over 90 minutes, carb-load: 7 to 10 g of carbohydrate per kg of body weight a day for 24 to 48 hours before.
Favour simple, low-fibre carbs, start the day big and taper, and introduce nothing new.
On the day, a carb-based meal 2 to 4 hours before, then a small low-fibre snack about 1 hour before.

During: keep the fuel coming

How long you go	Carbohydrate per hour
Up to 1 hour	Usually none needed. Water is enough, and a carbohydrate mouth-rinse can help hard efforts.
1 to 2.5 hours	30 to 60 g per hour, sipped or eaten regularly.
Over 2.5 hours	Up to 90 g per hour, from a mix of sources (drinks, gels, solids).

Above 60 g an hour, use mixed carbohydrate types (glucose plus fructose, about 2 to 1) for better absorption, and practise it in training so your gut adapts.

Hydration and sodium

Drink to thirst and to a plan, replacing what you lose in sweat. For long or hot events, include sodium (in drinks, gels or food) to protect against low blood sodium (hyponatraemia), and avoid over-drinking plain water.

Where to learn more: the NHS, the British Dietetic Association (BDA), and the Sport and Exercise Nutrition register (SENr). See also the Fuelling Around Training and Hydration guides.

This leaflet is general nutritional guidance for education only. It is not medical advice, diagnosis or treatment, and it does not replace advice from your GP or a registered dietitian. Always check with a qualified professional before making significant changes, particularly if you have a health condition, are pregnant, or take medication.