Fuelling during a HYROX® race: carbs, caffeine and fluids

Do you need carbs during a 60 to 100 minute fitness race?

Not strictly, but most athletes gain from small amounts. Reviews of exercise lasting about one hour find a benefit from a mouth rinse or small doses of carbohydrate, and no need for large ones. Past roughly 75 minutes the case for taking something in gets stronger, so we scale the amount to your expected finish time.

• About one hour of hard effort: a carbohydrate mouth rinse or small amounts can improve performance, and large amounts are not needed (Jeukendrup, 2014).
• Sustained high intensity of about one hour: small amounts, even a rinse, help through the brain's response to carbohydrate in the mouth. For longer sports, 30 to 60 g an hour is the usual target (2011 review).
• Across 61 performance studies of different lengths, 82 percent found a benefit from carbohydrate compared with water, and the gain grew with exercise time (systematic review, 2014).

Gels, a sports drink or nothing: what works in a fitness race?

A gel is the easiest way to take carbohydrate in a fitness race, because you carry it in a pocket and it needs no chewing. A sports drink gives fluid and carbohydrate together but must be carried. The form matters less than the amount, and the form you have practised matters most.

Gut trouble is the main risk. Studies suggest that 30 to 50 percent of athletes get stomach complaints in endurance exercise, and blood flow to the gut falls in intense exercise, especially when you are short of fluid (review, 2014). That is a reason to keep amounts modest and to practise. Our recommendation: under 75 minutes, water is enough. From 75 minutes, carry one or two gels you have already tested.

How many grams of carbs per hour, by finish time?

Use the table: nothing to about 25 g an hour for a finish under 75 minutes, up to 40 to 60 g an hour for 105 to 120 minutes. These are our recommendation, derived from the sourced ranges of small amounts at about one hour and 30 to 60 g an hour for longer efforts.

The rows assume a normal meal beforehand. We use 20 g of carbohydrate per gel in the examples. Products differ, so read the label and do the sum for yours. The upper end of each row is for athletes who have already practised eating at race effort. The guidelines come from trained athletes and may need to be adjusted downwards for less trained ones (Jeukendrup, 2014). Not sure of your finish time? Use the fitness race split calculator to estimate it.

When should you take carbs during the race?

Take them in the first half and in small portions, in the places where you walk or jog and can swallow safely. Do not wait until you feel empty. This is a timeline for a 90-minute finish, and it is our recommendation, so move the minutes in proportion to your own finish time.

1. Before the start: eat the meal you planned (see what to eat before a fitness race). A few sips of drink in the last 15 minutes are optional.
2. Minutes 0 to 25: water only while you settle into your pace on the first runs and stations.
3. Around minute 30 to 35: first gel, taken while you walk out of a station, with a few mouthfuls of water at the next water point.
4. Around minute 60: second gel in the same way.
5. Last 20 minutes: nothing new. Sips only. A gel in the final 10 minutes adds little and costs stomach comfort, in our judgement.

When should you take caffeine, and what doses have been studied?

Caffeine has some of the best evidence of any supplement for endurance performance. The studied dose is 3 to 6 mg per kg of body mass, most often taken about 60 minutes before exercise. If you already use caffeine, plan it from your wave time, and test it in a training session first.

• Studied doses: 3 to 6 mg/kg improved performance consistently. The minimum effective dose may be as low as about 2 mg/kg, and doses around 9 mg/kg brought many side effects without extra benefit (ISSN caffeine position stand).
• Arithmetic (ours): for a 70 kg athlete, 3 mg/kg is about 210 mg of caffeine in total, from all sources.
• Timing: about 60 minutes before the start is the most common choice. Chewing gum may need a shorter wait, and energy gels and chews with caffeine have also been studied (ISSN).
• Sleep: the half-life is 4 to 6 hours on average, and ranges from 1.5 to 10 hours between people, so an afternoon wave can affect the night after.

For the wider evidence on supplements, see supplements for a fitness race: what the evidence says.

How much should you drink during a fitness race?

Drink to thirst, with a few mouthfuls at the water points. Sweat rates vary from person to person, and a fixed plan rarely fits. In a 60 to 100 minute race we would rather you sip a little too little than force down too much.

• Sweat rates in adults range from about 0.5 to 4 litres an hour, so there is no single right volume (NATA position statement).
• A common aim is to avoid losing more than 2 percent of body weight to dehydration (ACSM position stand, 2007). Weigh yourself before and after a hard session to estimate your own sweat rate.
• Overdrinking beyond thirst is the main cause of low blood sodium in endurance events (review, 2017), so do not drink on a timer.
• Sodium: a systematic review found little evidence that taking sodium during exercise improves performance, with doses from 280 to 900 mg an hour tested (review). For an event this short we see no reason to take salt tablets. Longer races are different, see half-distance fuelling.

Our recommendation: take two to four mouthfuls at each water point and more on a hot day. If your mouth is dry or you feel thirsty, drink.

What do the transition zone and water points allow?

The 2026/27 Single rulebook guarantees water at least once around each pass through the transition zone. A sports drink may also be offered. If you want gels or anything else, you must carry them yourself from the start. Rules differ by season and event, so read the current version.

• Water is available at least once during, before or after each pass through the transition zone. Do not rely on a sports drink being there.
• Nutrition you want must be on your person from the start. You may not take drinks or food from anyone except the aid stations, which counts as outside assistance and can bring time penalties.
• Hydration packs are on the list of permitted items, and anything you carry must stay with you from start to finish.
• Throw used gel packaging into the bins. Littering can cost a 2-minute penalty.
• The fluids at aid stations are for drinking only. Pouring them over your head or body can cost 2 minutes, and spitting or clearing your nose on the floor is also penalised.

How do you test your fuelling plan before race day?

Rehearse it in the same kind of session, at the same time of day, with the same products. Race day is not the place to find out that a gel upsets your stomach at wall balls. Practise it in your hardest sessions of the plan.

1. Use the plan in two or three long mixed sessions, such as a compromised run with stations, and take the gels at the minutes in your table row.
2. Rehearse the practical side too: which pocket the gel is in, how you open it with tired hands, and where you put the empty packet.
3. Try caffeine once in a session of the same type and time as your race, and note how your stomach and heart rate respond.
4. In your peak weeks, run the whole plan in a simulation, as in the 12-week plan, and change one thing at a time if something goes wrong.