Race Shape › Answers › How should I pace a 70.3 half Ironman?
AnswersHow should I pace a 70.3 half Ironman?
Conservatively on the bike, so you can run. A Race Shape plan targets about 75% of FTP for a 70.3 bike leg — it feels far too easy for the first hour, and it is meant to. It then expects the run to be about 11% slower than your fresh half marathon, because nobody runs a half marathon off 90 km of riding at their standalone pace.
Targets for an FTP of 250 W and a 1:50 half marathon
| Leg | Target |
|---|---|
| Swim | Comfortably below threshold. Start wide, settle, then build |
| Bike average | about 188 W — 75% of FTP |
| Bike ceiling on climbs | about 208 W — do not chase the hill |
| Run | plan for about 2:02:06, not 1:50:00 |
| Run pacing | Easy first third, then hold or lift |
Why the bike is where the race is lost
Every watt above the target in the first third of the ride comes out of the run later, and it comes out at a bad exchange rate. Athletes who ride to feel rather than to a number almost always go too hard early, because fresh legs and adrenaline make threshold feel sustainable. It is not, for 90 km followed by a half marathon.
Fuel on a timer rather than on feel. By the time you feel hungry on the bike, it is too late to fix on the run.
Common questions
What if I do not have a power meter?
Ride by heart rate, staying in the endurance zone, and by perceived effort — conversational for the first hour.
Why is the full Ironman target lower?
A full-distance bike leg is twice as long and followed by a marathon. Race Shape targets about 68% of FTP for it.
How much slower is the run off the bike?
Race Shape plans for about 11% slower than a fresh half marathon at 70.3 distance, and about 20% slower than a fresh marathon at full distance.
Sources
- Race Shape engine rules: 70.3 race-day bike target 0.75 of FTP with a climbing ceiling of 0.83; run-off-bike factor 1.11 (70.3) and 1.20 (full distance).
- Allen, H. & Coggan, A. Training and Racing with a Power Meter.