Race Nutrition for Endurance Events (3+ hours)

During long-endurance events such as IRONMAN triathlons, marathons or long cycling races, your body burns around four times more calories per hour than usual. Because stored carbohydrate (glycogen) can run out after 90–120 minutes, you must replace carbohydrates, fluids and sodium during the race to maintain performance.

How Your Body Uses Energy

• You have plenty of fat stores — you don’t need to consume fat during the race.

• Carbohydrate stores are limited and deplete during long, hard exercise.

• Without carbohydrate replacement, your pace and performance drop quickly.

This is why regular fuelling is essential during long events.

Hourly Intake Guidelines

• Carbohydrate: 60–90 g per hour

• Fluids: Up to 1–1.2 litres per hour (depending on conditions and sweat rate)

• Sodium: 500–700 mg per litre, or up to 1,000 mg per litre if you are a “salty sweater”

Always check the nutrition labels of your chosen products (gels, bars, drinks, chews) so you know precisely how much carbohydrate and sodium you’re getting.

Fuel by Discipline

Swim Nutrition:

• You cannot eat or drink during the swim, so you must start well-fuelled.

• Take a gel or energy drink before the swim while waiting at the start — this tops up blood glucose so you reach the bike feeling strong.

Bike Nutrition:

This is the easiest stage to meet your fuelling needs. 

Hourly targets:

• Carbohydrate: 60–90g, such as:

  • 6 Clif Shot Bloks (~48–72 g)

  • Two-thirds of a Maurten 320 drink

• Fluids: 1–1.2 litres

• Sodium: 500–700 mg per litre (up to ~1,000 mg for salty sweaters)

Common options: Water, sports drinks, gels / chews, bars, sodium capsules, concentrated carbohydrate. drink mixes

Run Nutrition

Your gut is more sensitive during the run, so choose easier-to-digest options. 

Hourly targets:

• Carbohydrate: 60–90g 

• Fluid: sip to thirst

• Sodium: 500–700 mg per litre (up to ~1,000 mg for salty sweaters)

Well-tolerated choices:

• Sports drinks with 6–10% carbohydrate concentration

• Gels you know work for you

• Small amounts of fruit or Coke as needed in the latter stages

Example Full-Day Race Nutrition

Marathon (~4 hours): Carbohydrate target ~180 g

Example strategy:

• Two small bottles of Maurten 320 (~80 g carbs each)

• OR nine 20 g gels spaced every 20 minutes after 50–70 minutes

• Hydrate regularly and add sodium if sweating heavily

IRONMAN 140.6 (~13–14 hours): Carbohydrate target: ~840–1,260 g

Pre-race (waiting for swim):

• 500ml of Maurten 320 drink, consumed slowly over about an hour (80 grams carbs)

T1:

• Maurten gel (~25 g)

Bike (~790 g carbs):

• 2 litres Maurten 320 drink (~320 g)

• 1 litre water

• 1 mini peanut butter sandwich (~35 g carbs)

• 2 Maurten bars (~86 g)

• Salt tablets every 30–40 minutes

T2:

• Maurten gel (~25 g)

Run:

• Soft flask with 500 ml Maurten 320 (~160 g carbs)

• Water at aid stations

• Gel every ~45 minutes + salt tablets

Planning Your Nutrition

Before the Event

• Create an hour-by-hour fuelling plan.

• Practise all products in training to avoid race-day distress.

• Check what on-course nutrition is provided and test it in advance.

Gut Training

Your gut adapts over time — practising your fuelling plan during long rides and runs reduces the risk of stomach issues.

We recommend a carbohydrate product from the Swedish company Maurten (we have no ties to them). For endurance athletes, Maurten gels and drinks are potentially game-changing. They enable you to ingest more carbohydrates with less risk of getting jelly belly and other forms of gastrointestinal distress. A small Maurten 320 Drink Mix bottle contains 80 grams of carbohydrate, equivalent to four energy gels.

However, as with all energy products, it’s important that you use them regularly in training first. For example, Maurten energy gels are thick and can be hard to swallow sometimes. They may not suit you.

Adjust for Conditions

Increase both sodium and fluid intake in hot or humid weather or if you are a heavy sweater.

Health & Dietary Needs

Adjust your plan as needed and speak with a health professional if you have specific conditions.

After the Race

Refuel with carbs, fluids and electrolytes to support recovery.

Learn More

Watch Phil's video content:

Half Distance Triathlon

Marathon

Hydration

Further reading:

• Race Day Breakfast
• Fuelling Options
• Nutrition and Hydration Logistics

Looking for a more personalised approach?

You can benefit from expert nutritional guidance tailored to your training plan and specific needs, with Fuelin - the nutrition app for people who do endurance sports.

Fuelin syncs with TrainingPeaks and is programmed to recognize MyProCoach workouts. So that you can have a nutrition plan that matches your MyProCoach training plan, enabling you to consume the right foods and drinks at the right times.

Get 30% off with the discount code "MPC30". Please note this is a one-time use code available for monthly, quarterly or annual subscriptions). 

Copyright MyProCoach® Ltd © September 2023. All rights reserved.