Endurance fuelling
Race day fuelling schedule.
Turn a finish time, a carbs-per-hour target and a fluid rate into a stop-by-stop plan: what to take at each stop, with running totals.
Inputs
Plan
Enter your finish time.
How do I build a race day fuelling plan?
Pick a carbohydrate rate from the research range (30 to 60 g per hour, up to 90 g per hour past 2.5 hours; Burke and colleagues), pick a fluid rate that suits your sweat rate and conditions, then spread both across regular stops. The ISSN ultra-marathon position stand describes 450 to 750 mL of fluid per hour, or about 150 to 250 mL every 20 minutes. The ACSM position stand recommends customized fluid plans because sweat rates and sweat electrolyte content vary widely.
This schedule divides the event totals evenly across the stops, so the running totals end at exactly your hourly rates times hours. Stops fall at multiples of the interval; any time left after the last stop is not scheduled. Gel equivalents divide each stop's carbohydrate by your gel size and are not rounded to whole gels, so you can combine gels, chews and drink to hit the grams.
Frequently asked questions
How often should I eat and drink during a marathon?
There is no single published interval. The ISSN ultra-marathon stand describes about 150 to 250 mL of fluid every 20 minutes, and many plans take carbohydrate at the same stops. Choose an interval you can keep up and test it in training.
How many carbs per stop?
Hourly carbohydrate times the interval in hours. At 45 g per hour and a 20 minute interval that is 15 g per stop.
What if my event is not a whole number of intervals?
The plan uses whole stops that fit inside the finish time and spreads the totals evenly over them.
Where do the fluid numbers come from?
The 450 to 750 mL per hour figure is from the ISSN ultra-marathon stand. Your sweat rate, the heat and the ACSM goal of preventing more than 2% body mass loss from water deficit should shape your own number.
Sources
Checked
- Burke, Hawley, Wong and Jeukendrup, Carbohydrates for training and competition (IOC consensus), J Sports Sci 2011
- Tiller et al., ISSN position stand: nutritional considerations for single-stage ultra-marathon training and racing, J Int Soc Sports Nutr 2019
- Sawka et al., ACSM position stand: Exercise and fluid replacement, Med Sci Sports Exerc 2007
Ranges are quoted from the sources above and are general research or position-statement figures. Gel, powder and drink contents, spare gels and stop intervals are your own inputs; defaults are placeholders. One kilogram of body mass is treated as one litre of fluid.
Scope
Education only, not medical or dietetic advice. Needs differ by person, event, heat and training, and the published ranges are general. Try any fuelling or hydration plan in training, not for the first time on race day. If you have a medical condition (including diabetes, kidney or heart disease or high blood pressure), are pregnant or breastfeeding, or are under 18, ask your doctor or a registered dietitian first. Stop and get medical help for confusion, vomiting, severe headache, fainting or swelling of the hands and feet during or after a long effort.