Cycling

FTP calculator and cycling zones

Pick the test you actually did — 30 minutes, 20 minutes, or 2 × 8 — and get your FTP, your LTHR and the seven zones for each.

Which test to do

All three are valid and all three get you to the same place. The practical difference is what each one gives back:

30 minutes all-out. The most complete, and the one I recommend. It gives you FTP and LTHR from a single ride: average power for the 30 minutes is your FTP, and average heart rate for the last 20 is your LTHR. It's also the hardest to pace.

20 minutes all-out. Shorter and more repeatable. FTP comes from 95% of average power, because a 20-minute effort is held above true threshold. LTHR comes from average heart rate over the last 15 minutes.

2 × 8 minutes. Two maximal blocks with recovery between. FTP is 90% of the average of both. This test does not give you heart-rate zones: the blocks are too short for heart rate to settle where it needs to be. If you want HR zones, you need a continuous 20 or 30 minute effort.

Power or heart rate — which one leads?

If you have both, power leads. Heart rate lags behind the effort and moves with heat, sleep, caffeine and the stress of the day — two identical sessions can produce different heart rates with nothing at all having changed in your fitness. Power measures the work you're doing, directly.

That doesn't make HR useless: it's the best backup there is when you don't have a meter, and comparing the two across a block tells you things neither one says alone.

How to do the test properly

Rested, fed, chest strap on — a wrist sensor won't do for this. On the trainer, or on a stretch of road with no traffic lights, no long descents and no traffic forcing you to soft-pedal. Warm up seriously: 15 or 20 minutes with a couple of short accelerations before the block starts.

Go out even. The most common mistake is starting at the power you'd like to have and dragging yourself through the last eight minutes: the average comes out similar, but the test stops describing your threshold and starts describing your capacity to suffer badly distributed.