How To Pace Your Next Half Ironman

Swim, bike and run faster with this Ironman 70.3 triathlon pacing guide…

An Ironman 70.3 is the first step towards the world of long-distance triathlon. With its 1.9km swim, 90km bike and 21.1km run it’s an event that can take anything from four hours, right through to eight.

So let’s say for argument’s sake it takes you five or six hours. That’s a LONG time to be swimming, cycling and running, and you’ll need a pacing strategy that reflects that. If you treat it like it’s an Olympic distance triathlon you’ll pay a hefty price later in the day.

Thankfully the advice in this feature shows you how to pace yourself properly, so that you feel strong throughout. The secondary benefit of getting your pacing right is that it gives your body a fighting chance to process all the gels, bars and energy drinks that you consume during the event. So not only will this pacing strategy help you to race faster, but it will also keep you more energised along the way. Let’s start with the swim…

Half Ironman Swim Pace

This is the only time in the race when you should go above 6 out of 10 intensity – and only at the start. Aim for 8 out of 10 intensity initially and use the first 300 metres of the swim to find your place in the group and hopefully get in the draft-zone of similar-level (or slightly faster) swimmers. After a few minutes you should be able to ease back down to 6 out of 10 intensity and maintain that right through to the end of the swim. If you’re a nervous swimmer, start off at 6 out of 10 and stay out of harm’s way.


Transition 1.​

Don’t sprint like Usain Bolt and build up lots of lactic acid in your legs. This is a five or six hour race and you should not be out of breath. Jog into transition. You still need to be smart in transition – but save your legs for later.


Half Ironman Bike Pace

Use a power meter as your first guide, with heart rate as a backup. If you don’t have a power meter you can use heart rate and feel.  Aim to ride at a consistent power output with the difference between your average power and normalized power being as close to zero as possible. In other words, no spikes in power for hills or sprints. If it’s a hilly route, you might benefit from a compact chainring and a rear cassette with a 30 or 32 tooth chainring. This should give you enough gears to maintain a nice steady power output without spikes, on all but the hilliest routes.


Sub 5 hour Half Ironman Athletes:
  • 83 to 84% of your threshold power output (FTP).
  • 84-85% of your max heart rate
  • Feels like 6 out of 10 intensity.
5 to 6 hour Half Ironman Athletes:
  • 80 to 83 % of your threshold power output (FTP).
  • 82-84% of your max heart rate
  • Feels like 5.5 out of 10 intensity.
6 to 8 hour Half Ironman Athletes:
  • 77 to 80% of your threshold power output (FTP).
  • 80-82% of your max heart rate
  • Feels like 4.5 to 5 out of 10 intensity.

Transition 2

Jog. Be smart, don’t waste time. Save your legs for the run.


Half Ironman Run Pace

​If you paced the swim and bike sensibly, you’re in with a fighting chance of running to par. Either way, you’ll still be tired by the time you hit T2. After all you’ll have been racing for 3 to 6 hours already. So don’t expect to run fast like it’s an individual half marathon. Realistically you should be aiming for an intensity that’s similar or slower than your full-marathon pace.


Sub 5 hour Half Ironman Athletes:
  • 80-82% of your max heart rate
  • 90-91% of your 1-hour race pace
  • Feels like 5 out of 10 intensity.
5 to 6 hour Half Ironman Athletes:
  • 78-80% of your max heart rate
  • 87-89% of your 1-hour race pace
  • Feels like 4 out of 10 intensity
6 to 8 hour Half Ironman Athletes:
  • 76 to 78% of your max heart rate
  • 86-87% of your 1-hour race pace
  • Feels like 3.5 out of 10 intensity

Ironman 70.3 Strategy

​My final tip is to make sure you treat your half Ironman with respect. Use accurate and recent data to plan your pacing strategy, rather than guess work. As well as getting your pacing right, you need to think carefully about nutrition. This principles in this Ironman nutrition blog will help you. For more training advice check out our half Ironman schedules here.

By Phil Mosley.

Click Here to browse Phil’s 8-48 Week Half Ironman Training Plans for beginner, intermediate and advanced.

Copyright © 2016 Philip Mosley

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Phil Mosley (Coach & Founder)
Phil Mosley (Coach & Founder)

Phil is a recognised expert in the field, having featured on many endurance sports publications. He founded MyProCoach in 2010 to sell premium training plans complete with email coach support for triathlons, duathlons, running & cycling.

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