Carbohydrate loading has been practised by endurance athletes for decades. It works. But like most evidence-based strategies, the details matter, and the HYROX-specific context changes what correct carb loading actually looks like.
This article covers who should carb load before HYROX, who does not need to, exactly what to eat and when, and how to integrate HYDRAX PRIMER and HYDRAX CORE into your pre-race preparation.
Does Carb Loading Work for HYROX?
The short answer: it depends on how long your race will take.
Muscle glycogen (the primary fuel for high-intensity exercise) can be maximised by consuming elevated carbohydrate in the 24 to 48 hours before competition. When glycogen stores are saturated, you start the race with a larger energy reserve, which delays the onset of fatigue.
A meta-analysis published in the Journal of Sports Sciences confirmed that carb loading increases muscle glycogen concentration by 20 to 40% above normal levels, and that this consistently improves performance in events lasting 90 minutes or more (Hawley et al., 1997).
- Finishing under 60 minutes: Moderate carb loading is beneficial as standard pre-competition nutrition.
- Finishing 60 to 90 minutes: Full carb loading is recommended.
- Finishing 90-plus minutes: Carb loading is essential.
The Science: How Carb Loading Works
During rest, muscle glycogen is stored alongside water in a ratio of approximately 3g of water per gram of glycogen (Olsson and Saltin, 1970). When you carb load successfully, your muscles become physically heavier. You may notice a 1 to 2kg increase in body weight the morning of your race. This is normal and a sign it is working.
Modern research has shown that a depletion phase is unnecessary. Simply increasing carbohydrate intake 24 to 48 hours before competition while reducing training volume is sufficient (Sherman et al., 1981). You do not need to run yourself into the ground the week before HYROX to make room for carbs.
How Many Carbohydrates Do You Actually Need?
| Finish Time | Carb Target (per kg bodyweight, over 24 hrs) |
|---|---|
| Under 60 min | 5 to 7g/kg |
| 60 to 90 min | 7 to 9g/kg |
| 90-plus min | 8 to 10g/kg |
For a 70kg athlete targeting a 90-minute HYROX: 7 to 9g × 70kg = 490 to 630g of carbohydrate in the 24 hours before race day. Hitting the target requires intentional eating across every meal.
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The 48-Hour Pre-Race Meal Plan
2 Days Before HYROX (Day −2)
Begin shifting your diet toward carbohydrate-dominant eating. Reduce fibre, moderate protein, and minimise fat.
Breakfast: 100g rolled oats; 1 banana + 1 tbsp honey; 200ml orange juice (≈115g carbs).
Snack: 2 rice cakes with jam; 250ml sports drink.
Lunch: 200g cooked white rice; 150g grilled chicken; small serve steamed broccoli.
Snack: 1 banana; 1 slice white toast with honey.
Dinner: 200g dried pasta cooked; tomato-based sauce with lean mince; small side salad.
Day −2 total: approximately 435g carbs.
Day Before HYROX (Day −1): The Critical Day
Highest-carbohydrate day. Training should be minimal — a light 20 to 30 minute shake-out at most.
Breakfast: 2 cups cooked white rice or large bowl of oats; 2 eggs; 1 banana + honey (≈130g carbs).
Mid-morning: 2 slices white bread with jam; 300ml fruit juice.
Lunch: Large bowl white rice; 120g lean protein; steamed peeled potato.
Afternoon snack: 2 rice cakes with jam; 1 banana; half a serving of HYDRAX PRIMER in 500ml water (15g carbs + 650mg sodium to begin pre-loading electrolytes).
Dinner (3 to 4 hours before bed): 250 to 300g cooked pasta; simple tomato sauce; 100g chicken or tuna. No raw salad, no cruciferous vegetables, no legumes.
Day −1 total: approximately 595g carbs.
Race Morning (Day 0)
3 to 4 hours before race start: 1 cup cooked oats or 2 slices white toast; 1 banana; 1 tbsp honey; small amount of protein; 400 to 500ml water.
25 to 40 minutes before race start: One full serve of HYDRAX PRIMER in 400 to 500ml water — 29g dual-carb final top-up plus 1,313mg sodium pre-load. Sip over 15 to 20 minutes.
What to avoid: High-fat foods, high-fibre foods, protein-heavy meals without carbs, new foods, large volumes within 90 minutes of start.
Foods to Prioritise and Avoid
| Best carb-loading foods | Carbs per serve | GI Risk |
|---|---|---|
| White rice (200g cooked) | 52g | Very low |
| White pasta (200g cooked) | 62g | Very low |
| White bread (2 slices) | 40g | Very low |
| Banana | 25g | Very low |
| Oats (80g dry) | 55g | Low |
| Potato (peeled, 200g) | 36g | Very low |
| HYDRAX PRIMER (1 serve) | 29g | None |
| Foods to avoid (24 hrs before) | Problem |
|---|---|
| Wholegrain bread and pasta | High fibre, GI distress risk |
| Cruciferous vegetables | Bloating and GI distress |
| Legumes | Significant GI distress risk |
| High-fat meals | Slows gastric emptying |
| Alcohol | Impairs glycogen synthesis by up to 50% |
| Spicy food | GI irritation |
| New foods or supplements | Race day is not the time to experiment |
Addressing the Weight Gain Concern
For every gram of glycogen stored, the body stores approximately 3g of water alongside it. Successfully loaded, you may weigh 1 to 2kg more on race morning than your off-season weight. This is helpful weight — a fuel and hydration reserve that directly supports your performance.
Using HYDRAX in Your Carb-Loading Protocol
Day before (afternoon snack): Half a serve of HYDRAX PRIMER in 500ml water adds 15g of easily absorbed dual carbs and begins sodium loading.
Race morning: One full serve of HYDRAX PRIMER in 400 to 500ml water, 25 to 40 minutes before the race.
During the race: HYDRAX CORE handles the in-race carbohydrate and electrolyte delivery from approximately the 40-minute mark for 60-plus minute athletes.
PRIMER before. CORE during.
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Frequently Asked Questions
Will carb loading make me feel bloated or sluggish on race morning?
Some athletes experience temporary bloating. Reducing fibre and fat in your pre-race diet minimises GI discomfort. By race morning, most athletes feel energised.
I have a sensitive stomach. How do I carb load safely?
Prioritise low-fibre, easily digestible carbohydrates and liquid carbohydrates like HYDRAX PRIMER. Test your pre-race meal plan in training at least once before race day.
Should I reduce my training the week before?
Yes. Tapering training volume in the 3 to 7 days before a race allows glycogen stores to accumulate more effectively.
What if my race is early in the morning and I cannot eat 3 to 4 hours before?
Prioritise dinner the night before. On race morning, eat what you can 90-plus minutes before the start, and use one serve of HYDRAX PRIMER in 400ml water 25 to 40 minutes before the gun.
Read Next
- HYROX Nutrition Guide: The Complete Fueling Strategy for Race Day
- How to Fuel a HYROX Race: Your Strategy by Finish Time
- The Best Electrolyte Drink for HYROX Athletes
References
Hawley JA et al. (1997). Journal of Sports Sciences. | Olsson KE and Saltin B (1970). Acta Physiologica Scandinavica. | Bergström J et al. (1967). Nature. | Sherman WM et al. (1981). International Journal of Sports Medicine.