Essential Strategies for Fueling and Hydrating During Your Ironman or 70.3 | Plus Free Guide Download

Mark Cullen
3 days ago
4 min read

Preparing for an Ironman or 70.3 race demands more than just physical training. How you fuel and hydrate during the event can make the difference between finishing strong or struggling to cross the line. Proper nutrition and hydration strategies help maintain energy, prevent cramps, and support mental focus throughout the race. This post breaks down practical tips to help you optimize your fueling and hydration plan, plus offers a free downloadable guide to keep with you on race day.

How to Fuel for a 70.3 or Ironman Without Guessing

If you’re racing a 70.3 or an Ironman, your fueling and hydration plan matters just as much as your fitness. A lot of athletes spend months building their swim, bike, and run fitness, then completely wing their race-day nutrition. They show up with a rough idea to “eat a few gels,” grab whatever is on course, and hope for the best.

That’s exactly why I put together a free Fuel and Hydration Planner for 70.3 and Ironman athletes at the bottom of this page. It’s designed to help you stop guessing and start building a plan you can actually test in training.

Why fueling matters so much in long course triathlon

In a long race, you are constantly burning through energy and losing fluid.

You’re using carbohydrate stores from muscle and liver, sweating out fluid and electrolytes, and asking your gut to keep up while you’re under stress for hours. If you don’t stay on top of that, the cost adds up. Maybe it starts with a slight fade on the bike. Then your pace drifts. Then you stop wanting to eat. Then the run becomes survival mode and often times a walk in to the finish if you dont nail this.

That’s why a good fueling plan is less about doing something fancy and more about being consistent. The goal is to drip-feed the race with enough energy and fluid that you never dig too deep of a hole.

Fill in the free planner on Precisions Website to get your target totals The Fuel & Hydration Planner by Precision Fuel & Hydration

The biggest mistake athletes make

The biggest mistake is not having a real plan. They know what products they like. They know they should drink something. They know they should take in carbs. But they haven’t actually mapped out how many carbs per hour they’re targeting, how much sodium they’re getting, how much fluid they’re drinking, or whether it all works together at race intensity.

That’s where problems start.

A plan should answer things like:

How many carbs per hour are you aiming for on the bike?
How many carbs per hour are you aiming for on the run?
How much fluid are you taking in each hour?
How much sodium are you getting?
Are you taking Caffiene? When?
What products are you using?
When exactly are you taking them?
What happens if it’s hotter than expected?
What happens if your stomach starts to go sideways?

If you can’t answer those questions clearly, you probably don’t have a plan yet.

Bike fueling and run fueling are not the same

One of the biggest things athletes need to understand is that what works on the bike may not work as well on the run.

The bike is generally the best chance to stay ahead on fuel and hydration. You’re moving at a lower impact, it’s easier to drink consistently, and it’s easier to get in bigger amounts of carbs.

The run is different. Gut tolerance often drops, it’s harder to stay on top of intake, and athletes who got behind on the bike usually feel it here.

That means your bike plan needs to do a lot of heavy lifting.

A common mistake is underfueling the bike and then expecting to fix it on the run. That rarely works. The run is usually where poor execution gets exposed, not where it gets solved.

You need to test your plan in training

Race day is not the place to experiment. You should be testing your fueling plan in long rides, long runs, bricks, and race simulation sessions. That’s where you figure out what your gut tolerates, what intake feels realistic, what products sit well, and how your energy responds.

This is also where you learn whether your plan is actually practical. A plan might look great on paper, but if it’s too complicated to execute while riding hard, grabbing bottles, staying aero, and managing the chaos of a race, it’s not a good plan. That’s why I like athletes to track what they actually did, not just what they intended to do.

What to pay attention to in training

When you’re practicing fueling, don’t just ask whether you took in calories. Ask better questions.

What was your target for carbs per hour?

How much did you actually get in?

How much fluid did you drink?

How much sodium did that give you?

Did your energy stay stable?

Did you feel thirsty?

Did you get sloshy or bloated?

Did you have any GI issues?

Did the plan feel easy to execute?

Did you finish the session feeling like this could work on race day?

Those are the types of questions that help you refine a race plan over time.

Why hydration and sodium matter too

A lot of fueling conversations focus only on carbs, but hydration and sodium matter as well, especially in hotter conditions or for heavier sweaters.

If fluid intake is too low, performance can suffer and fueling can become harder to tolerate. If sodium intake is way off relative to your sweat losses and fluid strategy, that can create problems too.

This doesn’t mean you need to obsess over every milligram. But it does mean you should stop being vague.

“Drink when thirsty and hope for the best” is not much of a strategy for a race that lasts 5 to 7 hours or 9 to 15+ hours.

You want a plan that is specific enough to guide your decisions, while still flexible enough to adapt to weather, pace, and how you’re feeling on the day.