Race fueling

Your gut adapts to what you ask of it. Practicing carbohydrate intake while you train can improve how well you absorb it and is likely to reduce stomach trouble (Jeukendrup 2017). In one small trial, runners who practiced for two weeks had markedly fewer stomach symptoms (Costa et al. 2017). Race day is the wrong place to find out that a gel does not agree with you.

Use your long sessions, at close to race effort, to rehearse the whole plan: the breakfast, the timing, and the same food and drink you will race with. Afterwards, note whether you took it as planned, how it sat and how your energy held up late on.

In Splitpace, once you have an Olympic-distance race or longer, rides from 90 minutes are marked Fueling practice on your calendar, and so are runs from 75 minutes for a half or full distance.

The longer the race, the more your fueling decides how it ends. Typical finishing times vary widely, so read these as rough guides rather than categories.

Sprint

Many athletes finish in around an hour to an hour and a half. A familiar meal beforehand matters most; a sports drink or a little carbohydrate on the bike can help at the longer end.

Olympic

Often two to three and a half hours. Carbohydrate on the bike starts to matter, and it is the first distance where rehearsing your race fueling pays off.

Half

Often five to seven hours. Fueling runs from early on the bike through the run, and what you have practiced is what you race with.

Full

Often ten to seventeen hours. Fueling is a plan for the whole day, built up over months of training, including how you use what the aid stations offer.

Published guidance scales carbohydrate during exercise with how long the effort lasts. These general figures come from the joint position of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine (Thomas et al. 2016). They are not targets for you, and they are not set by body weight.

Under about 45 minutes

None needed.

About 45–75 minutes

Small amounts, or rinsing a sports drink around your mouth.

About 1 to 2½ hours

30–60 g of carbohydrate an hour.

Beyond about 2½–3 hours

Up to about 90 g an hour, built up gradually in training. Above about 60 g an hour this needs products that combine glucose and fructose, which the gut can absorb together faster than either alone.

Jeukendrup (2014) gives similar figures for well-trained athletes and notes that slower or less experienced athletes may need less. Treat them as a place to start testing, at the lower end, in training: the right amount is the one you have practiced and your stomach tolerates. You may read about professional cyclists taking far more; that is being studied in elite athletes and is not general guidance.

There is no single right volume: sweat losses differ widely between people and conditions, so fluid needs are individual (Thomas et al. 2016). Drinking when you are thirsty is the recommended guard against drinking too much (Hew-Butler et al. 2015), and some athletes work out a personal plan from their sweat losses with a sports dietitian.

Drinking far more than thirst asks, especially over many hours, can dilute the sodium in your blood to a dangerous level. This is exercise-associated hyponatremia, and it can be life-threatening. Sports drinks and salt do not protect you from it if you drink too much. Nausea, headache, confusion or unusual swelling during or after a long race need urgent medical help.

Heat raises how much you need, and salt needs vary widely between people. If you use an electrolyte drink or tablets, practice with them like anything else.

Nothing new on race day: no new food, drink or kit. Eat the breakfast you have practiced, the same length of time before the start.

Find out what the aid stations offer. If you plan to use it, try it in training; if not, carry your own. Plan the transitions too: what you pick up, what you take and where it goes.

In Splitpace, your race page has a race-week checklist and a place to write your fueling plan against how long each leg of your pacing plan takes. Go to My races.

A sports dietitian can help if stomach trouble keeps coming back in training, if you are building toward a longer race than you have fueled for before, or if you have food allergies or intolerances to plan around.

Talk to a doctor before changing how you eat and drink for training if you have diabetes, a heart or kidney condition or another medical condition, or if you are pregnant.

Stop and get medical help if you feel dizzy, faint, confused or unwell during exercise. Training and your health says more.

Talk to a doctor, too, if food or your weight has become hard to think about, or if you notice unexplained weight loss, missed periods or injuries that keep recurring. These can be signs that you have been short of energy for your training for too long, which can harm health and performance in athletes of any sex (Mountjoy et al. 2023).

Sources checked 23 September 2026.

• Thomas DT, Erdman KA, Burke LM (2016). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. Journal of the Academy of Nutrition and Dietetics 116(3): 501–528. doi.org/10.1016/j.jand.2015.12.006
• Jeukendrup AE (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine 44(Suppl 1): S25–S33. doi.org/10.1007/s40279-014-0148-z
• Jeukendrup AE (2017). Training the gut for athletes. Sports Medicine 47(Suppl 1): 101–110. doi.org/10.1007/s40279-017-0690-6
• Costa RJS, Miall A, Khoo A, Rauch C, Snipe R, Camões-Costa V, Gibson P (2017). Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Applied Physiology, Nutrition, and Metabolism 42(5): 547–557. doi.org/10.1139/apnm-2016-0453
• Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. (2015). Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Clinical Journal of Sport Medicine 25(4): 303–320. doi.org/10.1097/JSM.0000000000000221
• Mountjoy M, Ackerman KE, Bailey DM, et al. (2023). 2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine 57(17): 1073–1098. doi.org/10.1136/bjsports-2023-106994