Pacing Your IRONMAN 70.3 (Half Distance) Triathlon

IRONMAN 70.3 Swim: Start Smart, Stay Controlled

The 1.9 km (1.2-mile) swim is a significant challenge, but it’s just the beginning of a long race. You must balance speed with energy conservation to set yourself up for a successful bike and run.

How to Pace the Swim

• Start strong, then settle: The first 300 meters will feel hard, but settle into your target intensity as soon as possible. If you are a nervous swimmer, start steady and stay out of the way.
• Use drafting to save energy: Position yourself behind or slightly to the side of a swimmer, maintaining a steady pace.
• Use Rate of Perceived Exertion (RPE): Aim for a moderate but controlled effort that feels sustainable for much longer than the distance.

Common Swim Pacing Mistakes

❌ Going out too hard and fading – leads to exhaustion before the bike even starts.
❌ Following the wrong swimmer – ensure they are swimming straight and at the right pace for you.
❌ Not staying relaxed – tension wastes energy; stay smooth and efficient.

IRONMAN 70.3 Bike: The Most Important Part of Your Pacing Strategy

The 90 km (56-mile) bike leg is where smart pacing makes the biggest difference. Push too hard, and your half marathon will feel tougher than needed. Ride with patience and discipline, and you’ll pass others on the latter part of the bike and during the run.

How to Pace the Bike

• Use a power meter if possible: This is the best way to control effort.
• If no power meter, use heart rate and RPE.
• Be consistent: Avoid surging and big power spikes—these burn extra energy and hurt your run.
• Control effort on hills: Many athletes push too hard on climbs without realizing it. Use easier gearing and maintain an even effort.
• Expect others to pass you early on: Let them go. Many will fade later in the race while you stay strong.

Common Bike Pacing Mistakes

❌ Going too hard too soon – leads to a slow, painful run.
❌ Uncontrolled effort on hills – avoid burning extra energy.
❌ Ignoring your fueling plan – stick with your fuelling strategy to run strong.

Pacing yourself properly on the bike will help you run faster and feel fresher and more energized.

IRONMAN 70.3 Run: Survive, Then Thrive

By the time you start the half marathon, your body is already fatigued. The key is to start conservatively and stay steady. The best possible outcome is maintaining a consistent pace without fading or walking excessively.

How to Pace the Run

• Start at an easy pace: Don’t expect to run like it’s an individual half marathon. Realistically, you should aim for an intensity similar to or slightly slower than your full-marathon pace.

• Use all three pacing tools: RPE, Heart Rate, and Pace, as none are reliable in isolation. Many variables can affect them, such as wind direction, gradient, and cardiac drift (increased heart rate due to heat stress). 

• Hold back until halfway: If you feel strong at mile 6, you can gradually increase your effort.
• Use aid stations wisely: Walk if necessary to get fluids in, but keep moving forward.
• Expect mental challenges: Positive self-talk and breaking the run into small segments can help.

Common Run Pacing Mistakes

❌ Starting too fast – the downsides of starting too fast are far greater than the downsides of starting too slow.
❌ Not adjusting for conditions – heat, wind, and fatigue all affect pacing.
❌ Skipping nutrition – lack of calories and fluids can cause an energy crash.

🔗 Triathlon Race Pace Calculator

A well-planned race pace strategy can make or break your triathlon. Proper pacing helps you stay strong, avoid fading, and improve hydration and nutrition absorption. Use our Triathlon Race Pace Calculator to plan your pacing based on actual fitness, not guesswork. It works with thresholds like Functional Threshold Power (FTP), Pace, or simple Rate of Perceived Exertion (RPE) (1-10 scale).

Fitness Tests: Base Your Pacing on Real Data

Ensure you base your Half Distance Triathlon pacing strategy on real results from fitness tests in the last eight weeks. DO NOT GUESS!

Fitness Tests To Determine Your Thresholds

Final Thoughts: Pacing is Everything

Your IRONMAN 70.3 race isn’t won in the first hour—but it can be lost there. Stick to your pacing strategy, trust your training, and run your own race. Remember:

✅ Swim steady and controlled – don’t waste unnecessary energy.
✅ Bike with patience – avoid fading and run strong.
✅ Run smart – start slow, stay steady, and only push if you can in the final miles.

Pacing is the difference between finishing strong and struggling to the line. Get it right, and you’ll have your best IRONMAN 70.3 yet!