How much slower is running after cycling?
Running off the bike feels like running through wet cement for the first kilometre or two — the famous “jelly legs.” It is real, it is measurable, and it is the single most important thing to understand about long-course racing.
Estimate your off-the-bike pace →How big is the penalty?
For most age-groupers the off-the-bike run is roughly 8–25% slower than a fresh, standalone run at the same distance. A 5:30/km open half-marathon runner might race nearer 6:15–6:45/km off a 70.3 bike.
Two things drive the size of the penalty: how hard you rode, and how much run durability you have built. Ride conservatively and run a lot of bricks, and the penalty shrinks toward the low end.
Why it happens
Your legs have been locked into one repetitive, mostly-concentric motion for hours, blood is pooled in your cycling muscles, and your nervous system has to re-learn the running pattern. Add dehydration and depleted glycogen and the back half gets harder still.
How to shrink it
The penalty is trainable. The highest-leverage moves:
- Pace the bike by power or effort, not ego — the bike is a setup for the run.
- Do brick runs: a 15–40 minute run immediately off the bike, regularly.
- Fuel and hydrate on the bike so you start the run topped up.
- Practise your race-pace transition so the run does not start in a panic.
FAQ
Does the penalty ever go away?
It gets much smaller with training and smart pacing, but there is always some cost to running off a hard bike. The goal is to manage it, not eliminate it.
How do I estimate my own off-the-bike pace?
Use the brick calculator: enter your fresh run pace, the race distance and your durability, and it estimates your off-the-bike pace and the percentage penalty.
This is general guidance for healthy adults, not medical or coaching advice. Confirm cutoffs in your race’s official Athlete Guide and consult a professional before starting any program.