Carbohydrate Loading
Carbohydrate loading raises carbohydrate intake before prolonged competition to increase glycogen availability. Whether it is useful for HYROX depends on expected duration, prior diet, training and tolerance.
Definition and HYROX® relevance
Carbohydrate loading is a pre-event strategy used mainly for prolonged endurance demands. HYROX® alternates eight 1 km runs with eight stations, but finish duration and metabolic demand vary widely. No direct trial reviewed here shows that every HYROX® athlete benefits from loading or that late-race slowing identifies glycogen depletion.
HYROX® Singles Rulebook 2026/27 · ACSM/Academy/DC · Nutrition and Athletic Performance
Amounts are context dependent
Sports-nutrition guidance describes high carbohydrate availability around demanding endurance competition, with ranges up to 8–12 g/kg/day in some circumstances. That is a broad guideline, not a mandatory HYROX® dose. A small 2026 crossover study in 11 endurance-trained participants found higher muscle glycogen after 10 versus 6 or 8 g/kg/day for 48 hours, but it did not establish HYROX® performance or a universal optimum.
ISSN · nutrient timing position stand · Jones et al. · carbohydrate dose, glycogen and GI comfort
Before and during competition
Joint guidance commonly places a familiar pre-event carbohydrate meal within the hours before exercise and carbohydrate during extended high-intensity exercise around 30–60 g/hour. A 2024 meta-analysis found an overall endurance-performance benefit from carbohydrate during exercise, with larger effects in longer tests and time-to-exhaustion outcomes than time trials. Race duration, opportunity to consume, prior meals and gastrointestinal tolerance determine whether and how this applies.
ACSM/Academy/DC · Nutrition and Athletic Performance · ISSN · nutrient timing position stand · Ramos-Campo et al. · carbohydrate during endurance exercise
Food choice and safety
Choose familiar foods and practise the plan. Lower-fibre or lower-fat choices may reduce fullness or gastrointestinal burden for some people, but neither protein, fat nor fibre should be universally suppressed. High absolute intakes can be difficult to tolerate. Athletes with diabetes, gastrointestinal disease, food restrictions or other medical needs should use a registered sports dietitian or clinician for an individualized plan.
ACSM/Academy/DC · Nutrition and Athletic Performance · Jones et al. · carbohydrate dose, glycogen and GI comfort
Frequently Asked Questions
When should loading begin?
Endurance guidance often uses roughly 36–48 hours, but a HYROX® athlete’s need and dose depend on expected duration, habitual intake and tolerance.
ACSM/Academy/DC · Nutrition and Athletic Performance · ISSN · nutrient timing position stand · Jones et al. · carbohydrate dose, glycogen and GI comfort
Will loading always increase body mass by 1–2 kg?
No. Glycogen is stored with water, but individual scale change varies; a recent small trial found no detectable body-mass difference among its tested doses.
Jones et al. · carbohydrate dose, glycogen and GI comfort
Should I take carbohydrate during HYROX®?
It may help during longer efforts, but the amount and delivery must fit duration, prior fueling, access and practised gastrointestinal tolerance.
ISSN · nutrient timing position stand · Ramos-Campo et al. · carbohydrate during endurance exercise
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