Why Your 20-Minute FTP Test Is Probably Wrong

The 20-minute FTP test is the most widely used power test in cycling. It is also, for many athletes, producing a number that is 5 to 10 percent higher than their actual threshold power.

That matters. FTP is the foundation every zone, every interval, every training prescription sits on. If it is inflated, you are training in the wrong zones. Your Zone 4 efforts are actually Zone 5. Your "tempo" rides are edging into threshold territory. You dig a deeper hole than planned on hard days and under-recover as a result. Over months, the cumulative training stress miscalculation compounds.

Here's what the research says, why the 20-minute test fails certain athletes, and what to do about it.

Where the 20-Minute Test Comes From

The standard protocol says: ride flat out for 20 minutes, take 95% of your average power, and that is your FTP. The 5% discount exists because sustained 20-minute power typically sits above true one-hour power for most cyclists.

The problem is "typically." Research from the University of Colorado published in 2025 confirmed what many coaches had suspected: the relationship between 20-minute power and one-hour power varies substantially between individuals. For some athletes, 95% is accurate. For others, particularly those with a high anaerobic capacity relative to their aerobic base, 20-minute test power can be inflated by closer to 10%.

Why? Athletes who are naturally strong anaerobically can produce significantly more power over 20 minutes by drawing on anaerobic energy systems. That contribution masks their true aerobic threshold. The 5% discount does not account for this.

The Athletes Most at Risk of Overestimating

Criterium racers and sprinters. High-end anaerobic power inflates short-effort tests.

Newer cyclists. Without a well-developed aerobic base, a larger proportion of 20-minute effort comes from anaerobic sources.

Athletes who rarely train at true threshold. If you rarely spend time riding at FTP, your perceived exertion at test time may lead you to go harder than sustainable in the first 10 minutes, artificially inflating your result.

Anyone who is particularly good at suffering. Mental toughness can push your 20-minute power above your aerobic ceiling.

The Signs Your FTP Is Set Too High

You can often tell without a new test. Look for these patterns:

Your prescribed Zone 4 intervals feel significantly harder than expected from the first repetition, not just by the fourth or fifth. Threshold work should be hard but sustainable. If 2x20 at FTP feels like maximal effort in the first 10 minutes, the target is wrong.

Your heart rate at FTP power is consistently above your lactate threshold heart rate. Many cyclists have a rough sense of where their threshold HR sits from long training history. If power and HR don't align, something is off.

You cannot complete the prescribed interval volume. If your training plan calls for 3x20 at FTP and you regularly only manage 2x20, the FTP may be the problem, not your fitness or willpower.

Your performance data over time does not improve despite consistent training. Incorrect zones mean you are probably not spending enough time at the right intensities.

Better Testing Options

The Ramp Test

The ramp test has become the standard at TrainerRoad and several other platforms. You increase power by a fixed amount every minute (typically 20W) until failure. FTP is estimated at approximately 75% of the peak one-minute power you achieved before dropping out.

The ramp test is not perfect. It has its own weaknesses, particularly for athletes with very high aerobic capacity relative to their anaerobic ceiling, where it can slightly underestimate FTP. But for most cyclists, it is more accurate than the 20-minute test because it removes the pacing problem. There is no skill to distribute. You simply keep going until you cannot.

The 60-Minute Test

If you want an accurate FTP number, this is the only test that gives you a direct measurement rather than an estimate. Ride as hard as you can sustain for exactly one hour. Your average power is your FTP.

The limitation is obvious: a properly executed 60-minute effort is extremely demanding, and most cyclists either cannot or will not do it on a regular basis. Reserve this for key testing moments in your season, ideally twice a year.

Using Your Training Data

Modern analysis tools can estimate FTP from your accumulated power data without a specific test. If you have ridden a series of hard efforts over the past 90 days, best-average power curves can give a solid estimate. This approach is most reliable with a large volume of quality data.

VeloCoach uses your ride history to continuously refine FTP estimates alongside your CTL/ATL/TSB calculations, which means your training zones stay calibrated between formal tests.

What to Do If Your FTP Is Wrong

The simplest fix is to run a ramp test and use that result. If the ramp test gives you a number 10-15W lower than your current FTP, that is likely more accurate.

If you suspect your FTP is inflated but are not ready to test, you can apply a manual reduction of 5% to your current number and reassess after four weeks of training in the new zones. If interval completion improves and your recovery between hard sessions is better, you were probably training above your actual threshold.

Getting FTP right is not about being conservative. It's about training in the zones that actually produce the adaptations you are after. Threshold work at 95% FTP builds different adaptations than VO2max work at 110% FTP. When those zones blur because the base number is wrong, so do your training outcomes.

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