How to Test Nutrition Before a Race: A Runner's Guide

Table of Contents

• Step 1: Set Your Baseline Carbohydrate Intake Per Hour
  • How to Calculate Your Starting Point
  • Choosing Gels and Mixes That Match Your Target
• Step 2: Build Your Hydration Strategy Around Sweat Rate
  • Measuring Sweat Rate and Sodium Concentration
• Step 3: Start Practicing Race Day Nutrition During Long Runs
  • The Confidence Problem Nobody Talks About
  • Logistics of Testing in Real-World Environments
  • Building a Mental Cue
• Step 4: Gut Training for Endurance Athletes
  • Why the Gut Adapts
  • A Progressive Gut-Training Protocol
  • Practical Rules That Make It Work
  • Tracking Gut Tolerance and GI Distress
• Step 5: How to Test Nutrition Before a Race Without Breaking Your Training
• Common Mistakes When Testing Race Day Nutrition
• Frequently Asked Questions

Last Updated: September 27, 2026

Step 1: Set Your Baseline Carbohydrate Intake Per Hour

Learning how to test nutrition before race day starts with one number: your hourly carbohydrate target. Most endurance athletes land between 60g and 90g of carbohydrate per hour, but the right figure depends on your body weight, pace and gut tolerance.

How to Calculate Your Starting Point

Start conservative. Pick a number you can hit on every long run for two weeks.

• Under 2 hours of racing: 30-60g per hour
• 2-4 hours: 60-80g per hour
• Beyond 4 hours: 80-90g per hour, built up slowly

Track what you take in. Write it down. A simple note on your phone works fine.

Choosing Gels and Mixes That Match Your Target

Precision Fuel PF30 gels deliver 30g of carbs each. Maurten Gel 100 gives you 25g. Both absorb fast and sit gently on the stomach.

Two PF30 gels plus a scoop of Skratch hydration gets you to roughly 80g per hour. That combo is a proven starting point.

Step 2: Build Your Hydration Strategy Around Sweat Rate

Your hydration strategy matters as much as your carbs. Get it wrong and you'll cramp, slow down, or end up in a medical tent.

Sweat rate varies wildly between athletes. Some lose 500ml per hour. Others lose over 1.5 litres.

Measuring Sweat Rate and Sodium Concentration

Weigh yourself before and after a one-hour run. No fluid intake during the run. Every kilogram lost equals roughly one litre of sweat.

Do this test in similar conditions to your race. A cool morning tells you nothing about a hot afternoon.

For sodium, check the salt stains on your kit. Heavy white marks mean you're a salty sweater. You need more electrolyte replacement than the average runner.

Step 3: Start Practicing Race Day Nutrition During Long Runs

Practicing race day nutrition during long runs is where your plan either works or falls apart. Race day is not the time to try a new gel. But the deeper problem most runners face is not logistical, it is psychological. Trying something new under race pressure triggers anxiety, and anxiety itself changes how your gut behaves.

The Confidence Problem Nobody Talks About

Most fuelling advice assumes you will trust your plan on race morning. In practice, many runners abandon a tested plan in the final kilometres because doubt creeps in. The fix is not more information, it is repetition that builds genuine confidence.

• Run the exact sequence you will use on race day: same gel, same timing, same fluid.
• Note how you feel at the 60, 90 and 120-minute marks, not just whether your stomach hurt.
• Repeat the same protocol at least three times before you trust it.
• If a session goes badly, change one variable at a time rather than abandoning the whole plan.

Logistics of Testing in Real-World Environments

Real-world testing means carrying what you will carry on race day. Same belt. Same bottles. Same pockets. The goal is to remove every small decision from race morning.

CREWED Sub 3:00 Marathon Race Fuel Pack →

• Test opening gel packets while running, including with cold or wet hands.
• Practice drinking from aid station cups at pace, pinching the rim to avoid spilling.
• Try caffeine gels and note how your body responds, including sleep that night.
• Time your intake to match race-day intervals so the rhythm becomes automatic.
• Practise taking fuel on hills and in the final hour of a long run, when coordination is worst.

Building a Mental Cue

Pair each fuel intake with a simple cue, a word, a breath, a check of your watch. Over several long runs, that cue becomes a trigger that reminds you to fuel even when race-day adrenaline is pushing you to forget. This is the part of nutrition testing that competitors rarely cover, and it is often what separates a plan that works in training from one that survives race day.

Step 4: Gut Training for Endurance Athletes

Gut training for endurance athletes is the missing piece in most fuelling plans. Your stomach can learn to absorb more carbohydrate per hour, but only through repeated, progressive exposure during training. The gut is not a fixed limit, it adapts, much like muscle does.

Why the Gut Adapts

When you repeatedly take carbohydrate during exercise, the stomach empties faster, the small intestine upregulates its carbohydrate transporters, and the gut becomes less sensitive to the mechanical and osmotic stress of food moving through it. Most practitioners find meaningful adaptation takes three to six weeks of consistent practice, not a single long run.

A Progressive Gut-Training Protocol

Start at your current comfortable intake and build in small, repeatable steps:

• Week 1: Hit your baseline hourly carb target on every run over 90 minutes. No increases.
• Week 2: Add 5-10g per hour to one long run only. Keep the rest at baseline.
• Week 3: Hold the new higher intake on two long runs. If it sits well, add another 5-10g per hour.
• Week 4: Attempt your full race-day hourly target on one long run, then repeat it once more before tapering.

Practical Rules That Make It Work

• Take carbohydrate in small, frequent doses, roughly every 20 minutes, rather than large boluses.
• Pair gels with fluid. A gel taken without water sits heavily and slows gastric emptying.
• Use a mix of glucose and fructose sources where possible. Multiple transportable carbohydrates are absorbed through different pathways and are generally better tolerated at higher intakes.
• Keep intensity moderate during gut-training sessions. High intensity diverts blood away from the gut and makes tolerance harder to judge.

Tracking Gut Tolerance and GI Distress

According to Australian Institute of Sport sports nutrition resources, carbohydrate tolerance improves with repeated exposure during training, which is why race-day nutrition should be rehearsed, not improvised.

Step 5: How to Test Nutrition Before a Race Without Breaking Your Training

Testing nutrition before a race should never disrupt your training block. The trick is to fold it into sessions you're already doing.

Here is a simple four-week testing schedule:

Week	Focus	Session	What to Test
1	Baseline carbs	Long run	Current gel and timing
2	Hydration	Long run	Sweat rate and electrolytes
3	Higher intake	Long run	Add 5-10g carbs per hour
4	Race simulation	Long run	Full race-day protocol

Common Mistakes When Testing Race Day Nutrition

Testing nutrition before a race goes wrong in predictable ways. Avoid these and you'll line up far more confident.

• Trying new products on race day instead of in training
• Ignoring fibre intake the day before, which slows gastric emptying
• Skipping electrolyte replacement because it's "just a short race"
• Testing only once, then assuming it works
• Changing your plan because a training partner does something different

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Frequently Asked Questions

How many weeks before a race should you test your nutrition?

Start testing at least 8 to 12 weeks out, during your highest-volume training block. Begin with shorter long runs to establish gut tolerance, then increase carbohydrate intake per hour as your body adapts. The final 2 to 3 weeks before race day should be about confirming what already works, not experimenting. Tapering is not the time to try new gels or hydration mixes. Use at least three long runs above 90 minutes to rehearse your full race-day protocol, including timing, flavour rotation and fluid volumes.

What are the signs that your race-day nutrition plan isn't working?

Watch for bloating, cramping, nausea, sloshing in the stomach, or a sudden drop in energy that feels like hitting the wall. These signs often point to too much carbohydrate too quickly, a fructose-to-glucose ratio your gut cannot absorb, or dehydration that slows gastric emptying. If symptoms appear during a long run, note the time, the product and the volume. Adjust one variable at a time, such as reducing carbohydrate intake per hour by 10g or switching to a milder-flavour gel, then retest on the next long run.

Should you test new gels or supplements during a race?

No. Race day is for executing a plan you have already rehearsed in training. New products can trigger GI distress, flavour fatigue or unexpected blood glucose spikes when you least want them. If you want to try a different gel, do it during a moderate training run at least 6 weeks out. The CREWED Sub 3:00 Marathon Race Fuel Pack and Sub 3:30 pack are built around a tested combination of PF30 Gels and Skratch Sport Hydration, giving you a starting point to fine-tune during your final long runs.

How do you calculate your carbohydrate intake per hour for endurance events?

Start with 60g per hour for efforts under 3 hours, then build toward 80 to 90g per hour for longer races if your gut tolerates it. For example, the CREWED Sub 3:00 pack recommends 2 PF30 Gels plus 1 to 1.5 scoops of Skratch Sport Hydration each hour, which lands in that 80 to 90g range. Test this during long runs, adjust by 10g increments, and track how you feel at each hour mark. Individual tolerance varies, so your tested number matters more than any generic guideline.