How many carbs per hour during endurance exercise?

30–60 g per hour for efforts beyond about 90 minutes. Above roughly 2.5 hours, 60–90 g per hour is possible using a mix of glucose and fructose, which use separate intestinal transporters and so exceed the ceiling either sugar has alone.

Do you need carbs for a run under an hour?

No. Muscle glycogen covers roughly 90 minutes of hard effort. For shorter sessions, fueling during the session adds nothing beyond what you already have stored.

What is gut training for endurance athletes?

Practicing taking carbohydrate during training so the gut adapts to absorbing it under exercise stress. Absorption capacity is trainable, and attempting 80 g an hour on race day without having practiced is a common cause of gastrointestinal distress.

Fueling for endurance: the three numbers that matter

Carbohydrate per hour, fluid per hour, sodium per hour. Everything else in endurance nutrition is a refinement of those three.

The AIM teamNovember 7, 20264 min read

Endurance nutrition is surrounded by products and complexity. It reduces to three numbers per hour.

1. Carbohydrate: 30–60 g per hour

Muscle glycogen holds roughly 90 minutes of hard effort. Past that, performance falls off sharply unless carbohydrate is coming in.

Under 90 minutes: nothing needed. Water is fine.
90 minutes to 2.5 hours: 30–60 g per hour.
Beyond 2.5 hours: 60–90 g per hour.

That upper figure requires a mix of glucose and fructose: and the reason is specific: glucose absorption saturates around 60 g/hour because it uses one intestinal transporter. Fructose uses a different one. Combining them in roughly a 2:1 ratio lets total absorption exceed what either can manage alone. Most modern sports products are built around this.

In practical terms, 60 g/hour is about two gels, or 750 ml of a typical sports drink, or a banana plus a gel.

2. Fluid: 400–800 ml per hour

Sweat rates run 0.5–2 liters per hour depending on effort, heat and the individual, a several-fold range, which is why generic advice fails people at both ends.

Find your own: weigh yourself before and after an hour of training without drinking. Each kilogram lost is roughly a liter of sweat.

Then drink to roughly match, without trying to replace it all, some deficit during exercise is normal and fine. Aiming for zero loss is how people end up over-drinking.

3. Sodium: 300–600 mg per hour

Relevant beyond about 90 minutes, and more so in heat.

Sweat carries 500–1,500 mg of sodium per liter: varying a lot between people. If you finish sessions with white residue on your face or clothing, you are at the high end and should aim higher within that range.

This is the one genuine case for electrolyte products, not general wellness, but prolonged effort where sodium loss is real and plain water alone can dilute blood sodium.

Train the gut

The most common race-day failure is gastrointestinal, not muscular. Someone reads that 90 g/hour is possible, tries it for the first time on race morning, and spends the second half of the event regretting it.

Absorption capacity is trainable. Practice taking carbohydrate during long training sessions, building up over weeks. Use the exact products you plan to use on the day.

Nothing new on race day is advice about your stomach, not your shoes.

Before and after

Before: 1–4 g of carbohydrate per kg of body weight, 1–4 hours ahead, timed so it is digested. Low fiber and low fat, both of which slow gastric emptying.

After: carbohydrate to refill glycogen and 20–40 g of protein. The urgency depends entirely on when you next train, within a few hours it matters, tomorrow it does not, and the total across the day matters more than the timing either way.

Common questions

How many carbs per hour during endurance exercise?: 30–60 g per hour for efforts beyond about 90 minutes. Above roughly 2.5 hours, 60–90 g per hour is possible using a mix of glucose and fructose, which use separate intestinal transporters and so exceed the ceiling either sugar has alone.
Do you need carbs for a run under an hour?: No. Muscle glycogen covers roughly 90 minutes of hard effort. For shorter sessions, fueling during the session adds nothing beyond what you already have stored.
What is gut training for endurance athletes?: Practicing taking carbohydrate during training so the gut adapts to absorbing it under exercise stress. Absorption capacity is trainable, and attempting 80 g an hour on race day without having practiced is a common cause of gastrointestinal distress.