The 8-minute FTP test from Chris Carmichael swaps one long effort for two all-out 8-minute time trials, 10 easy minutes apart. Your FTP is 90% of the better of the two averages. 51 minutes in all, and easier to get your head round than 20 minutes in one go.
| Target | Zone | Time | FTP 200 W | FTP 250 W | FTP 300 W |
|---|---|---|---|---|---|
| 105–115% | 5VO2 Max | 16 min | 210–230 W | 263–288 W | 315–345 W |
Put this session on your bike computer or watch
Do the test from your bike computer, guided block by block. Then enter your new FTP and every session follows.
This test doesn't make you fitter: it measures. It estimates your FTP, the power you can hold for about an hour, from two 8-minute efforts. Over such a short effort you ride above threshold, at around 111% of your FTP if it's right (100 ÷ 90): the 90% factor brings that effort back to an hour. The second effort tells you something extra: if it stays close to the first, you recover well between hard efforts. Like any field test, it is an estimate, not a direct measurement.
Riders with a power meter or a smart trainer who have done some hard efforts before. Eight minutes is easier to break down in your head than twenty: it's the right test if the long effort of the 20-minute FTP test makes you lose the thread. If you'd rather not pace anything at all, the ramp test sets the power for you. No known FTP? Enter an estimate: the targets are only guides.
At the start of a training block, or every 4 to 6 weeks: a common guideline. Do it fresh, after one or two easy days, never the day after a hard session. Repeat it in the same conditions (time of day, equipment, route) so your results compare, and don't mix tests: an 8-minute FTP and a 20-minute FTP don't come from the same calculation. Once your FTP is updated, every watt target moves with it.
5′ at 45–55% FTP + 5′ at 56–65% FTP + 5′ at 66–75% FTP
15 minutes building from 45 to 75% of FTP, in 5-minute steps. CTS suggests slipping a few short accelerations into the warm-up; keep them light, the test starts straight after.
8′ at 105–115% FTP
8 minutes all-out, by feel. On a smart trainer, turn ERG mode off. Build the power over the first 45 to 60 seconds, as CTS advises, rather than going off like a sprinter. If your current FTP is right, your average will land around 105–115% of it: 263 to 288 W for an FTP of 250 W. Note your average power.
10′ at 45–55% FTP
10 genuinely easy minutes at 45–55% of FTP. Drink, let your breathing settle, and head back to the start if you're outdoors: the second effort has to be on the same stretch of road.
8′ at 105–115% FTP
8 minutes all-out, paced the same way: controlled start, steady effort, a lift at the end if there's anything left. This second effort often comes out a little weaker than the first: that's normal, and it doesn't skew the result. Note your average power.
10′ at 40–55% FTP
10 very easy minutes at 40–55% of FTP. Then the maths: your FTP is 90% of the better of the two averages. 290 W then 284 W give an FTP of 261 W.
The first four minutes of each effort go fine; the last two are very hard, and the recovery feels very short before the second. Guide: 9 out of 10 at the end of each effort. If your second average is clearly higher than the first, you probably held back on the first.
Eight minutes is short enough to tempt you into a fast start, and long enough to make you pay for it. Build the power over the first minute, then hold a steady effort: an average is built, not ripped out in the first 30 seconds.
One effort uphill and the other on the flat, or a tailwind one time out of two: the averages no longer compare. Ride both on the same stretch, flat or a steady climb, or on the turbo.
The protocol keeps the better of the two averages, not their mean. Some apps do the opposite: with 290 and 284 W, your FTP goes from 261 to 258 W. Pick one method and stick with it from test to test.
In ERG mode the trainer imposes a power: the opposite of an all-out effort. Turn it off for both 8-minute efforts.
A field test developed in 1994 by Chris Carmichael and physiologist Edmund Burke, described in The Time-Crunched Cyclist (Carmichael and Rutberg, VeloPress) and by the coaches at CTS, Carmichael's company. The 90% factor is their convention; no published independent validation was found. CTS describes a warm-up of 10 easy to moderate minutes with a few short accelerations, without figures: the 15-minute warm-up, the cool-down and the % FTP targets are Wattson choices; on the two all-out efforts those targets are only guides. Other tests use other factors: 95% over 20 minutes for Allen and Coggan, 75% of the best minute for the ramp test. Bottom line: a recognised coaching test, moderate confidence in the FTP estimate.
Take the better of your two 8-minute averages and multiply it by 0.90. 290 W then 284 W give an FTP of 261 W. Some apps average the two efforts first, which gives a little less: 258 W here. Both methods are out there; stick with the same one from test to test.
Because you can ride 8 minutes harder than 20: the shorter the effort, the further it sits above your FTP, and the lower the factor has to be to bring the result back to an hour. The 90% is the convention of CTS coaches, not a figure from an independent study.
The 8-minute test is easier to manage mentally and to fit into a busy week. The 20-minute test, being longer, is closer to riding at threshold, and many coaches see it as more representative for diesel-type riders. What matters most is sticking with the same test from one time to the next.
First, a second chance: if you paced the first one badly, the second rescues the result. Second, the gap between the two shows how you recover from a hard effort: a second effort close to the first is a good sign. A clearly better second effort suggests you were too cautious on the first.
Yes, and it is the easiest way to keep the conditions identical for both efforts. Turn ERG mode off, keep the room well ventilated, and use the turbo for your next tests too: an indoor result and a road result don't always compare.
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