Ironman 70.3 pacing strategy: swim, bike and run

Pace each leg for the run

The half marathon is where an over-paced bike shows up. Aim to arrive at T2 with energy left, not to win the bike split. A small time saving on the bike rarely repays a slower run.

Swim: start controlled

• Swim at a steady aerobic effort, slightly easier than your CSS pace.
• Avoid sprinting the first few hundred metres. Heart rate that spikes early is hard to bring down.
• Sight often enough to swim straight. Extra distance costs more than a slightly slower stroke rate.

Bike: ride to a power or effort cap

Choose a bike effort well below FTP that you have practised over race-distance rides followed by running. A coaching reference for trained half-distance athletes is around 80–85% of FTP, with lower targets for less experienced athletes; this is not a universal prescription. Keep power steady and monitor both average and normalized power.

• Hold back on climbs and in the first 20 minutes. Keep surges short.
• Start eating and drinking early, in the first 10 to 15 minutes.
• Keep an even effort over rolling terrain instead of attacking every hill.
• In the last 10 minutes, spin lightly and prepare for the run.

Run: build, then finish

Start the first 2 to 3 km at the pace you can hold comfortably, even if it feels slow off the bike. Settle into target pace through the middle, and only push in the final 3 to 5 km if you still can. Walk aid stations briefly if it helps you take in fluid and fuel.

Example split table for a 5:30 finish

This table is an illustration, not a prescription. Replace the numbers with your own targets in the Triathlon Pace Calculator.

Race-week checklist

• Know your target pace or power for each leg and write it where you can see it.
• Plan fuel and fluids for the whole race, and use what you practised.
• Check the course profile and the weather. Heat and wind change the numbers.
• Do not try new gear, food or pacing on race day.