How to do an FTP test indoors

Your FTP is the number every structured workout is built on. Here is how the two most common indoor tests work, which one to pick, and what to do with the result.

What FTP is

Functional Threshold Power (FTP) is roughly the highest power you can hold for about an hour. Training zones, interval targets and ERG mode all scale from it: a workout written as "4 × 4 min at 112%" means 112% of your FTP. If the number is wrong, every session is either too easy or too hard.

Indoors on a smart trainer is the best place to test: no traffic, no wind, no hills, and the same conditions every time you retest.

Option 1: the ramp test

The ramp test is short and needs no pacing. You simply ride until you can't hold the target any more.

1. Warm up for 5 minutes at an easy 100 W.
2. The target starts at 100 W and rises by 20 W every minute.
3. Keep your cadence steady and ride each step until you can no longer hold the target.
4. Your FTP is 75% of your best 1-minute power.

Example: your best full minute was 340 W, so your FTP is 0.75 × 340 = 255 W.

The ramp test is ideal for a first test. Riders with a very strong sprint can come out a little high, and very steady "diesel" riders a little low, so retest with the same protocol to compare like with like.

Option 2: the 20-minute test

The classic test. It takes longer and needs good pacing, but it's closer to what threshold actually feels like.

1. Warm up: 5 minutes easy, 5 minutes steady, 3 minutes light spinning.
2. Ride a 5-minute opener at about 110% of your current FTP to open the legs (hard, not all-out).
3. Recover for 5 minutes.
4. Ride 20 minutes at the highest power you can sustain for the whole effort.
5. Cool down for 5 minutes.

Your FTP is about 95% of your 20-minute average power. Example: 270 W average gives an FTP of 257 W.

Pacing tip: start the 20 minutes slightly below what you think you can hold and build in the last five. Starting too hard is the most common way to ruin this test.

Which test should you choose?

• First test or short on time: the ramp test.
• You know how to pace a long effort: the 20-minute test.
• Either way: stick to one protocol so your results stay comparable.

How to prepare

• Test rested: no hard sessions in the 1 to 2 days before.
• Eat as you would before a hard workout and have a bottle ready.
• Use a fan. Indoors you overheat long before you run out of power.
• Use the same trainer and setup each time, and calibrate it if your trainer recommends it.

After the test

Update your FTP and your power zones follow automatically. Retest every 6 to 8 weeks, or after a training block, to keep your targets honest.