70.3 race nutrition: carbohydrates, fluid and sodium per hour

Carbohydrates per hour

For endurance exercise lasting 1–2.5 h, common guidance is 30–60 g of carbohydrate per hour. For events longer than about 2.5–3 h, intake can increase up to about 90 g/h, using glucose–fructose mixtures at higher intakes. Choose a target you tolerate and have practised; 90 g/h is not mandatory.

Higher targets only work if you train your gut. Build up the amount in long sessions over several weeks instead of changing it on race day.

Fluid

About 400–800 ml/h is a common planning range, not a mandatory minimum or maximum. Adjust to thirst, measured sweat losses, conditions and tolerance; do not force extra fluid just because it is hot. Avoid drinking enough to gain body weight during the event.

Estimate sweat loss in training: (pre-session body mass in kg minus post-session body mass in kg + fluid drunk in litres minus urine in litres) ÷ duration in hours ≈ litres per hour. Weigh without wet clothing and in comparable conditions. This is an estimate, not a requirement to replace every litre lost.

Sodium

A commonly cited starting range for prolonged endurance exercise is 300–600 mg of sodium per hour, but needs vary with sweat rate, sweat sodium and food/drink intake. Higher intake is not automatically better. Sodium does not prevent exercise-associated hyponatremia if you drink too much fluid. Sports drinks, gels and electrolyte tablets all contribute, so count them together.

Sodium is not the same as salt: 300–600 mg of sodium is approximately 0.76–1.53 g of salt (sodium chloride). Check whether product labels list sodium or salt.

Where to take it: bike first

• Take most of your fuel on the bike. It is easier to eat and digest while riding.
• Keep fueling on the run in smaller amounts, using gels or drink from aid stations.
• Set a timer for every 15 to 20 minutes so you do not forget.

Worked example

Target: 90 g per hour on the bike for 2:45 and 60 g per hour on the run for 2:05.

With gels that carry 25 g each, 373 g is about 15 gel equivalents between bike and run, excluding breakfast and pre-start intake. You need fewer gels if part of the carbohydrate comes from your drink or other food. This is an arithmetic example, not a universal nutrition plan. The Triathlon Race Nutrition Planner does this arithmetic for your own targets.

Practice rules

• Race with the products you trained with. Check which ones the race provides on course.
• Test the full plan in at least two long sessions.
• If you have a medical condition, or you take medication that affects fluids or blood sugar, check your plan with a doctor or a sports dietitian.