Fueling for race day: the night before, race morning, long runs and cramps

What you eat the day before, the morning of and during a long race can change the result, and the answer depends more on how long the race lasts than on its distance. This guide shows how much carbohydrate to eat for your weight, how much to carry on a long run and what to do about cramps, in the moment and at your next race.

The day before and race morning: how much to eat for your weight

A review showed that carbohydrate loading in the days before delayed fatigue by about 20% in endurance exercise and improved performance by 2% to 3% in fixed-distance events longer than 90 minutes; below that, there was no clear gain [1]. In practice, 5 km and 10 km races usually fall below that line, a half marathon depends on your pace and a marathon almost always goes beyond it.

At the London Marathon, runners who ate more than 7 g of carbohydrate per kilogram of body weight the day before ran faster, in an observational study [2]. For well-trained athletes, a review cites 10 g to 12 g per kilogram 36 to 48 hours before [3]. Start at the lower end.

A sample day for 60 kg, with 50 g bread rolls and bananas of about 80 g peeled: at breakfast, 2 rolls, 1 banana and 1 spoon of honey (about 95 g of carbohydrate); at lunch, 300 g of rice and 200 g of boiled cassava (about 145 g); as a snack, 200 g of corn couscous and 1 banana (about 70 g); at dinner, 250 g of rice, 1 roll and 1 banana (about 120 g). Total of about 430 g. For one day, cut back on foods very high in fiber and fat.

On race morning, eat about 4 hours before: in one study, 312 g of carbohydrate at that time improved performance by 15%, while 45 g and 156 g did not change the result [4]. With a very early start, eat less and closer to it; a review found no harm in eating carbohydrate at least 60 minutes before [5]. Choose what usually sits well, such as bread with banana, tapioca and couscous: there is no clear benefit in seeking special low-glycemic-index foods [6]. In races with a swim, avoid eating in the 30 minutes before the start [7].

In a small study, women stored more muscle carbohydrate only when they also ate more total calories [8], and a review recommends going above 8 g per kilogram, with attention to the day’s calories [9]. In 7 cyclists who ate carbohydrate during 100 km, loading did not change their time [10], and the 1-day load was tested in only 8 athletes at rest [11].

Long runs: how much carbohydrate to carry per hour

The amount depends first on how long the session lasts. A review of 136 studies found a larger effect in tests to exhaustion and in less-trained people [12], and general recommendations rise with duration [13].

The banana math is ours: in one study, 794 g of banana added up to 150 g of carbohydrate, about 23 g per fruit [14]. For gels and drinks, check the carbohydrate line on the label. Liquids, gels or solids low in fat, protein and fiber all work [13]; over 75 km of cycling, bananas and a sports drink gave similar times, but with bananas the cyclists felt fuller [14]. In real-world races, conclusions apply mainly to trained male cyclists in events over 90 minutes [15].

• Note the duration of your next long run and check the table.
• Start below the ceiling, spreading the amount across the session, and drink water with it.
• Watch your stomach and performance; test in training, never for the first time on race day.

Cramps: what to do in the moment and at your next race

In the moment, slow down or stop and gently stretch the muscle until the cramp passes, the measure with the strongest recommendation in a 2022 review [16]. Afterward, rest a little before resuming, because it can come back. Bananas are not a quick fix: in 9 men, blood potassium only rose after 1 hour and stayed in the normal range [17]. A small amount of acidic liquid, such as pickle juice, shortened a lab-induced cramp by 49 seconds [18], but race tests are lacking.

For prevention, pace matters more than the bottle. In a 56 km race, runners who cramped covered the first 28 km 13 minutes faster, with similar personal bests [19]. Cramps usually come from several factors combined, such as muscle fatigue and intensity above what was trained [20], and drinking more did not guarantee protection [21].

How CatLena uses it

On the Nutrition screen, the day’s carbohydrate appears with its target and how much is left. In the example below, the person had eaten 128 g of a 467 g target, with 339 g to go. The day before a long race, this bar shows whether the planned load is on track, meal by meal.

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