Eight kilometres of running, with a station after every kilometre, from the sled to the wall balls. You train for a HYROX for weeks, and part of that work can be lost in the last twenty-four hours, with a high-fibre dinner the night before or a start on an empty stomach. What you eat comes down to four moments, the day before, three to four hours before the start, the last hour and the race itself.
A race that runs on carbs
HYROX is a glycolytic sport, one that draws mainly on carbs, like CrossFit, interval training or combat sports. Above 60 to 65% of VO2max, the body burns mostly carbs, and at moderate intensity, the liver's glycogen lasts about 100 minutes and the muscles' about two hours. When glycogen runs low, fatigue hits all at once.
A German team had eleven recreational athletes race a simulated HYROX in the official format. Their median time was 86 and a half minutes, almost all of it at hard or very hard intensity, with the highest values at the end, on the wall balls (Brandt et al., 2025). At that intensity, glycogen supplies most of the energy, and you fill it up the day before.
The day before, fill up
The benchmark is 6 to 8 grams of carbs per kilo of body weight, or about 500 grams for 70 kilos. At 60 kilos that is 360 to 480 grams, at 80 kilos 480 to 640 grams. It takes about 24 hours for the body to store these carbs in the muscles and liver, which is why you start the day before and not on race morning. Protein stays at around 2 grams per kilo, and fat makes up the rest.
The next morning, the scales will probably show a little more. Each gram of stored glycogen holds about three grams of water, and that extra weight tells you your reserves have filled up.
This kind of loading is for the day before a competition and has no place in the way you eat the rest of the year.
Low fibre that day
Eating 500 grams of carbs in the form of wholegrain foods would give you more than 60 grams of fibre, twice a normal day, with a real risk of digestive trouble during the race. So the day before, you pick simple, easy-to-digest carbs such as white rice, potatoes, fruit, honey or dates. The rest of the time, my benchmark is 13 to 15 grams of fibre per 1,000 calories, and I explain it in the article on fibre.
In The Athlete's Fuel, every example relies on carbs that do not feed inflammation. White rice, potatoes, sweet potatoes, chestnuts and polenta for meals, fruit, dates and honey around training. They cover an athlete's needs, including on very high-volume days.
Race morning, a light meal three to four hours before
Three to four hours before your start, have a meal with 60 to 90 grams of carbs, low in fibre, easy to digest and something you enjoy eating. A banana, honey, a few dates, a little white rice. If your heat starts at 11 am, that meal goes in between 7 and 8 am. Eating early is hard, even if you are used to it, and a light, tasty meal goes down far better than a big plateful.
Fruit, dates and honey have another advantage. The gut absorbs glucose through one door that lets in about 60 grams an hour, and fructose, the sugar in fruit, through another, at about 30 grams an hour. Mixing the two gets more carbs through without overwhelming the gut, and these foods naturally provide both sugars.
Just before the start, a drink
Thirty to sixty minutes before, one last top-up of about 30 grams of carbs, in drink form. It completes your hydration and nudges your blood sugar up just before the start, so you dip less into your reserves. Definitely not a zero-sugar drink, since sugar is exactly what you are after.
During the race
For an hour of effort, nothing. The reserves you filled the day before are enough. I put the limit between one and two hours. Beyond that, you need to take in carbs during the effort. If you are aiming for something closer to 1 hour 30, like the recreational athletes in the German study, a drink that hydrates and brings a little sugar is enough. Top up just before you start with a small sugary drink, which kicks in after about thirty minutes, then take a few sips all the way through the race to keep your blood sugar up. Around the one-hour mark, drink a little more.
The weeks before
Never test a strategy on race day. Pick a big session at the time of your future heat, and rehearse the planned morning, the meal three to four hours before, then the drink. Write down what sat well and what did not, and adjust. The gut can be trained like a muscle.
For hard sessions in the build-up, do not start completely fasted. A small hit of sugar is enough, without overloading the system, for example a spoonful of honey with a pinch of salt before the session.
This article is for information only and does not replace medical advice.