Race Nutrition for Endurance Events (3+ hours)

This article shows you how to get your race-day nutrition right and increase your chances of having a good race. 

During IRONMAN (Full or Half-Distance) Triathlon Races and Endurance Events, you burn four times more calories per hour than usual. Despite burning so many calories, you barely feel like eating or drinking in the race's latter stages, which is why you need to plan your nutrition carefully.

The energy you need for endurance events comes from a 65% carbohydrate and 35% fat ratio. Thankfully, we all have enough fat in our bodies, so we don’t need to consume any more during the race. However, our carbohydrate stores will run out after around 90-120 minutes.

To stay energised and healthy, you need carbohydrates, water, and salt (arguably). The more palatable your nutrition choices, the more you’ll be able to consume.

There is a new type of carbohydrate product from the Swedish company Maurten (we have no ties to them). The world’s top marathon runners use Maurten products, often without sponsorship.

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.

After working with over 40,000 athletes, here’s how we recommend you prepare for your event: endurance triathlon, running, or cycling.

If you plan to use on-course nutrition products (see the event website or event guide to find the products offered), you should use them during your training sessions in preparation for race day. Otherwise, experiment with products. Look for ones that contain multiple sources of carbohydrates (e.g., glucose and fructose) that suit your gut and taste good. The more palatable your nutrition choices, the more you’ll be able to consume.  

Swim Nutrition 

Consuming gels or drinks during an IRONMAN swim is impractical, so don’t bother. Just ensure you’re fuelled up beforehand (see Race Day Breakfast).

Bike Nutrition

Taking on nutrition on the bike is easiest because you can carry bottles, bars, and gels. Your upper body is static, which makes it easier to consume food and drink on the move. Think of it as a buffet on wheels. We’ll explain how much to consume later, but for now, here’s what to carry.

• OPTION 1: Water for hydration, carbo-chews such as Clif BLOKS Energy Chews, gels or bars for carbohydrates. SaltStick capsules for extra salt, depending on your sweat rate.
• OPTION 2: Maurten 320 Drink Mix and nothing else. This drink is easiest on your gut, so you’ll absorb more carbohydrates. It also takes care of your hydration needs. If it’s a hot day and you’re sweating a lot, consider using Maurten 160 Drink mix instead. This is the same product but half as strong, so there’s more water to quench your thirst. Maurten drinks do contain some salt, but not that much. On hot days, you may need to supplement this with SaltStick capsules (or similar).

Run Nutrition

For IRONMAN athletes, your gut will be compromised by the time you get to the run, and you need to treat it kindly. It can be the same for marathon runners; this is where people struggle. It is common to get jelly belly, cramps and diarrhoea – or just feeling plain exhausted. Your nutritional strategy can help.

• Energy drinks, ideally, with a 6-10% concentration of carbohydrate, so your gut can cope.
• Avoid energy gels and bars. Their carbohydrates are very concentrated and can cause gastrointestinal distress at this stage of the race.
• If you can’t cope with energy drinks, regularly sip Coke instead. It is like pure sugar and enters your bloodstream before reaching your stomach. Consume anything else you feel like – small bits of fruit often work well when you’re feeling lousy.

All Endurance Events: Race Day Nutrition Plan

Before your endurance race, you should make a detailed hour-by-hour nutrition plan. It can be a time-consuming exercise, but it’s totally worthwhile. You don’t have to memorise it perfectly, but it’s still better than making it up on the day.

Below, you will see the recommended total carbohydrate, fluids and sodium intakes per hour that you will need during your race to sustain your energy, hydration and electrolyte balance throughout.

We’ve written mostly in metric units. If you use US ounces, see the calculators below.

• You can calculate grams to US ounces here.
• You can calculate kilograms to pounds here.

You’ll need to study the nutritional information on packets and stick with mostly carbohydrate products. 

Pre-Event

Check this article to learn more about Race Day Breakfast

Event Nutrition

Swim

Just before the start:

• Carbohydrate: 5–30 grams, 5-30 minutes before. For example, a half or full energy gel, or a few swallows of energy drink.
• Fluid:  Ad-lib, to thirst.

Bike

• Carbohydrate: 60-70 grams of carbohydrate per hour. Some athletes may tolerate up to 90 grams. For example, six Clif Shot Blocks or 2/3 of a bottle of Maurten 320 every hour.
• Fluid: Maximum absorption is usually 1–1.2 litres per hour (32 to 40 fl. oz.) Depending on your sweat rate.
• Sodium: 500-700 mg/litre of fluid (32 fl. oz.). Salty sweaters: up to 1,000 mg/litre (32 fl. oz.)

Run

• Carbohydrate: 40-50 grams of carbohydrate per hour. Little and often. For a standalone marathon, you may be able to tolerate up to 60 grams of carbohydrate per hour.
• Fluid: Drink to thirst or dehydration level; sip little and often.
• Sodium: 500-700 mg per litre of fluid (32 fl. oz.). Salty Sweaters: up to 1,000 mg/Litre (or 32 fl. Oz)

Examples

4-hour marathon, aim for around 180 grams of carbs. You should be well-fuelled pre-race and have enough for the first 50-70 minutes. After that, you will need to top up your levels, for example:

• Sip from two small Maurten 320 Drink Mix bottles containing 80 grams of carbohydrate - each equivalent to four energy gels.
• Or nine gels containing 20 grams of carbohydrate (one every 20 minutes after the first 50-70 minutes).

13-14-hour IRONMAN 140.6, aim for 840g to 1260g carbs.

• Pre-race (waiting for swim start)
  • 500ml of Maurten 320 Caf, consumed slowly over about an hour (80 grams carbs)
• T1
  • Maurten gel (25 grams carbs)
• Bike (Total: circa 790 grams carbs, 2-3 litres of fluid and 4,000mg sodium)
  • 2 litres of Maurten 320 Caf (320 grams carbs), plus another litre of plain water
  • 1 small peanut butter sandwich for variety/real food (35 grams carbs)
  • 2 Maurten bars (86 grams carbs)
  • Salt tablet every 30-40 mins, depending on temperature
• T2
  • Maurten gel (25 grams carbs)
• Run
  • Carry a soft flask with 500 ml Maurten 320. Sip regularly - if logistics allow, carry mix and refill  for another 500ml (160 grams carbs)
  • Supplement with sips of water at aid stations
  • Maurten gel every 45 mins and a salt tablet.

Key considerations

• If you have pre-existing health factors and/or dietary restrictions, you may need to consult a doctor and/or make adjustments to your nutrition plan.
• Obtain the many essential vitamins and minerals from a varied and balanced diet.
• Your resting metabolic rate and daily activity level determine your energy needs.
• Your hydration plan should take into consideration your sweat rate and climate.
• Replenishing fluids and electrolytes can prevent dehydration and hyponatremia.
• Post-race nutrition helps replenish the body, restore muscle, replace fluids and sodium lost to sweat and respiration and provides the nutrients needed for muscle repair.

Learn More

Videos

Full Distance Triathlon

Half Distance Triathlon

Marathon

Hydration

Articles

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.

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