Cycling Race Day: Fueling, Hydration and Heat

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Ninety miles into a hundred-mile gravel race, the rider who looked strongest at the start is sitting on the side of the road, unwrapping a gel too late. In cycling that’s called bonking: the tank is empty, the legs stop, and no amount of willpower fixes it. Race day in cycling is unusual among sports because you can eat and drink while you compete, and because many events last hours. That makes what you eat and drink on the bike almost as important as your training. This page covers race-day fueling, carbs per hour, hydration and heat for every kind of event, from a 45-minute criterium or a high school mountain bike race to a gran fondo, a 200-mile gravel day or a Grand Tour stage.

General guidance for healthy riders. If you have diabetes, a heart or kidney condition, high blood pressure or special diet needs, follow your doctor’s or a registered dietitian’s plan. For an overview of the sport, see our cycling hub.

The days before and the morning of

The joint position statement on nutrition and athletic performance from the American College of Sports Medicine (ACSM), the Academy of Nutrition and Dietetics and Dietitians of Canada is the reference most sports dietitians use. For cycling it says:

• Carb loading is for long events. For events of more than 90 minutes, it describes 36–48 hours of 10–12 g of carbohydrate per kg of body weight a day. For shorter races, normal fueling (7–12 g/kg in the day before) is enough.
• Pre-race meal: 1–4 g of carbohydrate per kg, eaten 1–4 hours before the start. For a 70 kg rider, that’s 70–280 g, depending on how early you eat.
• Keep it low in fat, protein and fiber to lower the risk of stomach trouble, and pick foods you’ve tested in training: oatmeal, white rice, bagels, bananas, toast with honey.

Carbs per hour: how much to eat on the bike

Your muscles store only so much carbohydrate. In long races you need to top it up as you go. The ACSM statement and an earlier International Olympic Committee-backed review by Burke, Hawley, Wong and Jeukendrup give the same ladder:

Race length	Carbs during the race	Examples
Under 45 minutes	Not needed	Short time trial, short track
45–75 minutes	Small amounts, even a mouth rinse	Criterium, short circuit race
1–2.5 hours	30–60 g per hour	Road race, cross-country mountain bike, shorter gran fondo
Over 2.5–3 hours	Up to 90 g per hour, using glucose + fructose mixes	Long road races, gravel, century rides, stage races

Why glucose plus fructose? The body absorbs the two sugars through different routes, so a mix lets you take in and use more carbohydrate per hour than glucose alone, as Asker Jeukendrup’s research on “multiple transportable carbohydrates” showed. Many gels and drink mixes are built that way. What 60 g an hour looks like:

• Two Maurten Gel 100 gels (25 g carbs each, maker figures) plus a few sips of sports drink, or
• One bottle of Skratch Labs Hydration Sport Drink Mix (about 19–20 g carbs per scoop, so 2–3 scoops in a big bottle) plus a gel, or
• Real food: a banana plus a rice cake or bar (check the labels to count the grams), which work best early in long, steady rides.

Train your gut. The ACSM statement says athletes should practice to find a fueling plan that suits their goals and gut comfort. Jumping from 30 g to 90 g an hour on race day is a recipe for stomach cramps. Build up on long training rides, and eat early and often: a little every 15–20 minutes beats a lot at once. Our best energy gels guide compares carbs, sodium and caffeine per gel.

Hydration on the bike

• Start hydrated. ACSM suggests about 5–10 mL of fluid per kg of body weight in the 2–4 hours before exercise (350–700 mL for a 70 kg rider), aiming for pale yellow urine.
• During: the National Athletic Trainers’ Association (NATA) advises keeping body-mass loss to no more than about 2%, and not drinking so much that you gain weight, which can lead to dangerously low blood sodium (hyponatremia). When you don’t know your sweat rate, drinking to thirst is a safe approach.
• Know your sweat rate. NATA says competitive athletes should. Weigh yourself before and after a typical hour-long ride (minus what you drank); each kg lost is about a liter of sweat.
• Sodium matters for heavy, salty sweaters in long or hot races, NATA notes. Electrolyte drinks or tablets like Nuun Sport (300 mg sodium per tablet, maker figures) help many riders.
• After: ACSM suggests replacing 125–150% of the fluid lost.

Carry what you need. A standard bike has room for two bottles; for long or remote events, plan for refills at aid stations or feed zones, or add a hip pack or hydration vest.

Racing in the heat

Heat is now a regular part of race day at every level. At the 2026 Tour de France, organizers shortened stage 9 from 185.5 km to 155.5 km after French weather authorities issued a red alert for an “exceptionally intense heatwave”, with temperatures near 38°C forecast at the start. Since 2024, the UCI’s High Temperature Protocol rates heat risk using the wet-bulb globe temperature (WBGT), which combines air temperature, humidity, sun and wind:

• White to yellow (under 23°C WBGT): very low to moderate-low risk.
• Orange (23–27.9°C): moderate-high risk. Shaded starts, more neutral motorbikes with drinks and ice, and relaxed rules on drinking and cooling during the race.
• Red (28°C and above): high risk. Start times can change, part of the stage can be neutralized, or the race cancelled.

For the rest of us, NATA’s heat-illness guidance applies: acclimatize over 7–14 days of gradually longer, harder sessions in the heat before a hot event; start cool; pour water over your head and neck; slow down when the heat climbs. The airflow from riding hides how hot you are, until you stop on a climb. Warning signs of exertional heat stroke are confusion, odd behavior, stumbling or collapse. That’s a medical emergency: NATA says to cool first (cold-water immersion is most effective) and transport second when medical staff are on site, and to call 911.

Storms on the course

Gravel and mountain bike riders can be far from shelter. NATA’s lightning guidance: “When thunder roars, go indoors.” If you can hear thunder, lightning is close enough to strike, and no place outside is safe. Substantial buildings and fully enclosed metal vehicles are. Wait 30 minutes after the last thunder before riding again.

Race-day checklist

• Bike: tires checked, brakes working, chain lubed, a spare tube or plugs, a pump or CO2, a multitool.
• You: helmet, race license or registration, sunscreen, chamois cream, a rain jacket if the forecast says so.
• Fuel: enough gels, bars and drink mix for your carbs-per-hour target, plus a spare; bottles filled; a plan for refills.
• Warm-up: longer and with a few hard efforts before short races like crits and time trials; easier before long road and gravel races.
• Caffeine: many riders use caffeinated gels late in a race (for example Maurten’s CAF 100 has 100 mg). Caffeine isn’t for everyone, especially with heart problems, pregnancy or sensitivity, and never try it first on race day.

Young racers mostly need water, a normal meal a few hours before, and a snack for longer races; sports drinks can help in long, hot events, but energy drinks and stimulants don’t belong in a kid’s race bag.

Supplements and sports foods: follow the label, and check with your doctor or a dietitian if you have high blood pressure, kidney or heart problems, or follow a low-sodium diet. After the finish, see cycling recovery for refueling; for daily eating and supplements, cycling nutrition; and for drink mixes compared, our best electrolyte powder guide. Team-sport players can find the same science applied to halftimes on the soccer game day page.

Race day: FAQs

How many carbs per hour should I eat while cycling?

For rides and races of 1–2.5 hours, ACSM guidance is 30–60 g per hour. For efforts over 2.5–3 hours, up to 90 g per hour, ideally from glucose-fructose mixes. Under 45 minutes you don’t need any. Build up to higher amounts in training first.

What is bonking in cycling?

It’s riders’ slang for running out of stored carbohydrate: sudden weakness, heavy legs, sometimes dizziness or irritability. Eating carbs regularly from early in a long ride is the best way to avoid it. If it happens, stop, eat and drink something sugary, and ride easy.

How much should I drink during a race?

Enough to limit weight loss to about 2% of body weight, but not so much that you gain weight, per NATA. Learn your sweat rate by weighing before and after training rides. If you don’t know it, drinking to thirst is a safe approach.

What should I eat before a bike race?

A carbohydrate-based meal 1–4 hours before, low in fat and fiber, using foods you’ve tested: oatmeal, rice, bagels, bananas. ACSM guidance is 1–4 g of carbs per kg of body weight, with more when you eat earlier.

Can races be stopped for heat?

Yes. Under the UCI’s High Temperature Protocol, at the red level (WBGT 28°C and above) organizers can change start times, neutralize part of a stage or cancel it. At the 2026 Tour de France, stage 9 was shortened by 30 km during a red heat alert.