The Biggest Mistake You Can Make on Race Day

If you're running a long distance event this fall, you've likely put in most of your important training at this point. It's time to start visualizing race day and making a plan! 

The biggest mistake runners make on race day is  under-fueling.

Not eating enough during the race will sabotage your performance, no matter how well prepared you are. 

Don't throw months of hard work out the window because you weren't eating enough to performance to your best potential. 

The Signs You’re Not Fueling Enough

In my own running career, my biggest challenge has been finding the best fueling options for me and how to maintain energy levels in the last 10K of a marathon (or 5K of a half marathon). 

I've had to visit the medical tent at the finish line of a few of my races because I was hypoglycemic (completely drained of resources and energy). 

Before I started fueling enough, I always came shy of the performance I was looking for and it lead to a lot of frustration.

Because most runners underestimate how much energy they burn at race pace. If you’ve noticed any of these signs, there’s a good chance you’re under-fueled:

• You feel strong early, but crash hard in the last 4 - 6 miles of a half marathon or the last 6 - 8 miles of a full.

• Your pace suddenly drops even though your training shows you’re capable.

• You get mentally foggy, cranky, or hit the dreaded “wall.”

• Your legs feel heavy and depleted even though your fitness is solid.

These aren’t “just part of racing.” They’re your body telling you it’s out of readily available fuel.

Why Fueling Matters

Here’s the physiology, simplified:

Your body stores a limited supply of glycogen (carbohydrate) in your muscles and liver—about 90 minutes’ worth at race pace. Once that runs out, your body is forced to rely more heavily on fat as fuel. While fat stores are basically unlimited, fat is much slower to convert into usable energy.

That’s why runners who under-fuel slow down dramatically. It’s not a lack of willpower or poor training—it’s biology.

The good news? You can prevent this by topping off your glycogen stores during the race. Think of it like keeping gas in your tank. A steady trickle of fuel keeps you moving smoothly all the way to the finish.

During-Race Nutrition Guidelines

So what does fueling enough actually look like?

General rule of thumb:
👉 Aim for 40–60 grams of carbs per hour (about 100–240 calories per hour).

For Example:

• Gels: Most standard gels contain 20–25g of carbs (~100 calories). That means taking 1 gel every 30–40 minutes.

• Chews: A sleeve of chews usually equals ~40–45g of carbs. 

• Sports drink: Many sports drinks provide 30–45g of carbs per 16–20 oz bottle. 

• Real food options: Half a banana, a fig bar, or other small carb-rich snacks can also work, especially for longer marathons or ultras. Just note that they don't come with supplemental electrolytes like most sports gels, chews, or drinks.

Tips to make it work:

• Start fueling early—20–30 minutes into the race. Don't wait until you're well into your race to start!

• Break your fueling into small, frequent bites. It’s easier on the stomach and maintains steady energy.

• Always take fuel with a few sips of water to help absorption and reduce GI distress.

• Practice fueling during your long runs so your gut is ready on race day.

Practical Application

Let’s break it down for different race situations:

Half Marathon (~2 hours):

• 2–3 gels spaced 35–40 minutes apart.

• Some water or sports drink at aid stations.

• Example: Gel at mile 4, gel at mile 8, optional gel at mile 11 for a strong finish.

Full Marathon (~4–5 hours):

• 6–8 gels total or the equivalent mix of gels/chews/sports drink.

• Alternate between gels and sports drink if you prefer variety.

• Example: Gel every 30–40 minutes from mile 3–4 onward, alternating with sips of sports drink.

The most common mistake: skipping that final gel because “you’re almost done.” That last gel is exactly what you need in the final miles because otherwise you're essentially running on empty.

Quick Takeaways (Pin These to Your Race Plan)

• Take in 40–60g of carbs per hour (~100–240 calories).

• Start fueling 20–30 minutes into the race.

• Space out intake—about every 30–40 minutes.

• Mix gels, chews, sports drink, or real food.

• Don’t skip late-race fuel—it gives you your strongest finish.

Closing Thoughts

Your training gets you to the starting line. Your fueling gets you to the finish line feeling strong.

Under-fueling is one of the most common mistakes I see runners make.

But the good news? It's 100% within your control, unlike most factors on race day. This month, use your long runs as practice. Test your fueling strategy. Train your gut, find what works best for you, and go into race day with confidence that you’ll have the energy you need to finish strong.

You’ve put in the miles! Don’t let your nutrition be the missing piece.

Product Recommendations

• SIS (Science in Sport): Known for their isotonic gels that are thinner and easier to swallow without needing water.

• Maurten: Uses hydrogel technology to deliver carbs with minimal stomach distress, popular with elite marathoners.

• Tailwind: A drink mix that combines carbs, electrolytes, and hydration in one easy-to-digest formula.

• Clif Bloks: Chewy, bite-sized carb blocks that are easy to portion out during runs and come in multiple flavors.

• Honey Stinger Chews: One of the originals in endurance fueling, offering a wide variety of flavors and caffeine options.

Questions about this topic? Reply to this email and we can talk more about it. 

 ➡️ Reply to me directly at [email protected] to ask your questions or share your experience while dealing with running related injuries.

👟 Unsure how to balance it all? Reach out to me for 1:1 Run Coaching for your half, full or ultramarathon! We talk about nutrition, race, and training plan strategies that'll work for YOU and YOUR goals. 

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