The HYROX fueling protocol
A 75–90 minute race at threshold burns through more carbohydrate than most athletes start with. Here is the arithmetic, then the protocol, with a calculator that does the sums for your body weight.
Here is a pattern anyone who has watched a HYROX event will recognise. An athlete moves beautifully through the SkiErg, the sleds, the burpees. Somewhere on run five their stride shortens. By the sandbag lunges they are negotiating with each leg individually. At the wall balls they are a different person from the one who started.
The standard explanation is "they went out too hard." Sometimes true. But the less discussed explanation is arithmetic: a 75–90 minute race at threshold burns through more carbohydrate than most athletes start with, and nearly all of them refuel as if it were a 45-minute gym session, which is to say, not at all.
This piece is the arithmetic, and then the protocol. Jump to the calculator if you're racing this weekend. Read the middle if you want to know why, because a protocol you understand is a protocol you'll actually follow at minute 60, when your brain is running on fumes and bad decisions.
The physiology: what HYROX actually costs
Your muscles hold roughly 400–500 g of glycogen when fully loaded. Call it 1,600–2,000 kcal of premium race fuel. A HYROX effort at threshold intensity burns carbohydrate at somewhere between 2.5 and 4 g per minute, depending on your size and pace. Do the multiplication for a 90-minute race and the problem states itself: demand can meet or exceed the entire tank.
Two things make HYROX worse than a road race of the same duration:
The stations spike intensity above threshold. Sled pushes and burpee broad jumps are near-maximal muscular efforts. Every spike above threshold burns glycogen disproportionately and adds lactate you then carry into the next run. A half marathon is a steady withdrawal; HYROX is a series of large, badly-timed ones.
The format suppresses your gut. High-intensity work diverts blood from the digestive tract. That's why fueling during HYROX must be engineered: small doses, race-appropriate formats, practised in training, rather than improvised at a table between stations.
And in India, add the third variable: sweat. Even in an air-conditioned arena, an athlete acclimatised to Indian heat sweats hard, commonly 1–1.5 litres per hour at race effort, carrying a very individual amount of sodium with it (the published range across athletes is roughly 200–2,000 mg per litre, which is why your training partner's hydration plan is not your hydration plan). Cramp at the lunges is frequently a fueling-and-sodium story wearing a fitness costume.
Sweat is personalSodium loss ranges from roughly 200 to 2,000 mg per litre between athletes. That twenty-fold spread is why borrowing a training partner's hydration plan is closer to guessing than to planning. Test your own.
Fig. 02 · Glucose and fructose cross the gut wall through different transporters. Using only one jams a single door at roughly 60 g/hour; blending opens a second. This is the constraint ENDUURR's C-Series is being engineered around.
The 48 hours before: load, don't stuff
Carb loading has a folklore version (eat a mountain of pasta the night before) and a physiology version. The physiology version:
- From 48 hours out, bias meals toward carbohydrate you already know agrees with you: rice, idli, dosa, poha, chapati, potatoes, fruit. Aim high, in the region of 6–8 g of carbohydrate per kg of body weight per day for a full load.
- Reduce fibre on the final day. This is not the weekend for a farmhouse salad experiment.
- The night before, eat a normal-sized, carb-forward dinner. The load has already happened; dinner is just the top-up.
- Hydrate across the whole 48 hours, with electrolytes if you've been training in heat, not four frantic litres on race morning.
The Indian kitchen, it turns out, is a carb-loading instrument of unusual precision. Rice, idli and poha are exactly the low-fibre, high-glycaemic carbohydrates sports-nutrition textbooks describe. Your grandmother was periodising before it had a name.
Race morning: the 3-hour countdown
- T-minus 3 hours. The main meal: 2–3 g of carbohydrate per kg. Familiar, low-fat, low-fibre. Poha, upma, bread and jam, rice and curd if that's your normal. Nothing new. Nothing new is the entire rule.
- T-minus 60–90 minutes. A small top-up if you want one: a banana, a slice of bread with honey.
- T-minus 15–30 minutes. 20–30 g of fast carbohydrate: a gel or equivalent, with a few sips of water. If you use caffeine, this is its slot, roughly 2–3 mg/kg, and only if you've rehearsed it in training.
- Sip, don't chug. About 500 ml of fluid across the final 2 hours, with sodium if you're a heavy or salty sweater.
During the race: small, early, practised
The window to fuel in is the run legs and the Roxzone, never mid-station. The principles:
- Start before you need it. Gut absorption lags by 15–20 minutes. Fuel taken at the rowing station rescues the wall balls, not the rowing.
- Dose small and often. 30–60 g of carbohydrate per hour, split into 2–3 doses, beats one heroic gel at halfway.
- Anchor doses to the format. The natural slots: after station 2 (sled push) and after station 5 (rowing).
- Fluid at every opportunity, in sips. 100–150 ml at a time. A full cup sloshing through burpee broad jumps is a lesson you learn once.
- Doubles racers: you have no excuse. Your partner is working while you rest, so you have scheduled fueling windows built into the race.
Fuel taken at the rowing station rescues the wall balls, not the rowing.
All of it (dose, format, timing) gets rehearsed in training simulations first. Race day is the exam, not the lab.
Ranges, not prescriptions. Every figure here is the published working range, and your own gut and sweat test should narrow it. Rehearse the whole plan twice in training before you race it. Not medical advice.
Fig. 03 · Drag the sliders. Everything recalculates from the numbers in this article.
After: the unglamorous 60 minutes
Recovery is where adaptation happens, and it begins with refilling what the race emptied: carbohydrate (~1 g/kg in the first hour or two), protein (20–40 g), fluid and sodium (weigh yourself before and after a hard simulation once. Each missing kilo is roughly a litre owed, plus its salt). A proper meal within a couple of hours does most of this without ceremony. The athletes you'll race next season are the ones who treated the hour after this race seriously.
Fig. 04 · Ticks are saved in this browser, so you can open it again on race morning.
Frequently asked questions
Should I fuel for a sub-70-minute HYROX?
Yes, lighter: the pre-race doses as above, plus one 20–30 g dose mid-race. Below an hour of work the case weakens; HYROX rarely stays below an hour.
Can I just use water and bananas?
You can finish on them. Thousands do. Racing to your potential is harder: a banana mid-race is slow to eat and slower to absorb under load. We take the comparison apart properly in what is an energy gel?
What about Doubles?
Same totals, easier logistics: fuel during your partner's station work. The failure mode is different, and resting doesn't rescue your gut as much as teams assume. A dedicated piece on Doubles fueling is in production.
This protocol is general sports-nutrition guidance, not medical advice; athletes with medical conditions should confirm specifics with a qualified professional.