Pacing Your IRONMAN 70.3

Learn how to structure your race pace strategy to optimise your potential in your IRONMAN 70.3.

An IRONMAN 70.3 can take anything from four to eight hours. So let’s say, for example, it takes you six hours. That’s a LONG time to be swimming, cycling and running, and you’ll need a pacing strategy that reflects that. 

IRONMAN 70.3 Swim

During the first 300 metres of the swim you’ll find yourself swimming hard, without even trying. As soon as you can, settle down and find your place in the group and hopefully get in the draft-zone of similar-level (or slightly faster) swimmers. Ease down to a moderate intensity and maintain that right through to the end of the swim. If you’re a nervous swimmer, start off steady and stay out of harm’s way.

There are several ways to pace yourself, including heart rate, pace and RPE. From a practical point of view, using RPE (feel) works well – it saves you trying to look at your watch.

Rate of Perceived Exertion

  • First 300 metres, your intensity in Z4 and feel 7 to 8 out of 10 (feeling hard)
  • After the first few minutes, intensity should then dial down to a moderate High Z3 to Low Z4. Feeling like 6 to 7 out of 10 (where 10 is your hardest)

Max Heart Rate

  • First 300 metres your intensity should be 87 to 93% of your Maximal Heart Rate
  • For the remainder 80 to 87%
  • Beats Below Maximum Heart Rate: 20 to 40 beats


  • Take your fastest training pace for a 100, and then add 5 secs per 100 to get your IRONMAN 70.3 swim race pace
  • If you’re racing in a wetsuit, make sure you base your pacing strategy on your recent wetsuit training times (and vice versa)

IRONMAN 70.3 Bike

​The bike section is where pace judgement is most vital. Riding too hard will make your run much tougher than it should be (it will already tough enough!). Try to avoid these 3 common mistakes.

  1. Attempting to ride at a constant power output that is slightly too high.
  2. Riding in bursts, ranging from easy to hard – without realising.
  3. Riding too hard on the hills without realising, due to inappropriate gearing.

It is important to not base your pace-strategy on the bike split that you would ‘ideally like to do’. Use the pacing guidelines below and be realistic with your goals.

Power Output

 IRONMAN 70.3 Target    % FTP
 Sub 5 hours    83 to 84% 
 5 to 6 hours    80 to 83%
 6 to 8 hours    77 to 80%

Max Heart Rate

 IRONMAN 70.3 Target    % Max HR
 Sub 5 hours    84 to 85% 
 5 to 6 hours    82 to 84%
 6 to 8 hours    80 to 82%

Rate of Perceived Exertion (where 10 is the hardest)

 IRONMAN 70.3 Target    RPE (feel)    Zone
 Sub 5 hours    6 out of 10    Mid to High Z3
 5 to 6 hours    5 out of 10    Low to Mid Z3
 6 to 8 hours    4/5 out of 10    High Z2 to Low Z3

Riding at the right intensity takes discipline and courage, especially when other people are overtaking you. But it really works. Get it right and later in the bike and then on the run you’ll be passing those who passed you. You’ll also find that you can better digest your nutrition helping you maintain your energy levels going into the run. You will run faster as a result of pacing yourself properly on the bike, and you’ll feel fresher and more energised.

IRONMAN 70.3 Run

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 the run course. After all you’ll have been racing for 3 to 6 hours already. So don’t expect to run like it’s an individual half marathon. Realistically you should be aiming for an intensity that’s similar or slightly slower than your full-marathon pace.

Max Heart Rate

 IRONMAN 70.3 Target    % MHR
 Sub 5 hours    80 to 82% 
 5 to 6 hours    78 to 80%
 6 to 8 hours    76 to 78%


 IRONMAN 70.3 Target    % Threshold Run Pace
 Sub 5 hours    90 to 91% 
 5 to 6 hours    87 to 89%
 6 to 8 hours    86 to 87%

Rate of Perceived Exertion (where 10 is the hardest)

 IRONMAN 70.3 Target   RPE (feel)    Zone
 Sub 5 hours    5 out of 10    Low Z3
 5 to 6 hours    4 out of 10    High Z2
 6 to 8 hours    3.5 out of 10    Mid Z2

Using all three of the methods above (HR, Pace, Feel) is best as none of them are completely reliable in isolation. There are many variables that can affect them such as wind direction, gradient and cardiac drift (an increase in heart rate due to heat stress). The downsides of starting too fast are far greater than the downsides of starting too slow.

For all Disciplines

Ensure you base your IRONMAN 70.3 pacing strategy on real results from fitness tests done in the last 8 weeks. DO NOT GUESS!!

Your run success will be determined by how hard you went in the bike and swim sections – and your nutritional strategy. If you cycle too fast you will struggle on the run. If you pace the bike section intelligently and get your nutrition right, the chances are you’ll run well.

The longer you anticipate you’ll take to complete your IRONMAN 70.3, the lower your intensity should be. For example, if you think you’ll take 7 or 8 hours in total, you should aim for the lowest possible end of the pace, heart rate and exertion suggestions above.

Good Luck for your IRONMAN 70.3!

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