FTP Testing for Cyclists and Triathletes

FTP is the power you can hold for roughly an hour. That is the whole definition, and it is worth being honest about what the number is: an estimate, not a lab truth. Every field test approximates it from a shorter or differently shaped effort, and every approximation has a bias. What makes FTP useful anyway is what hangs off it. Your power zones, your training stress scores, your interval targets, and the coach's read on whether a session was hard or easy all anchor to this one number. A stale or inflated FTP corrupts everything downstream. A reasonable one, tested the same way each time, is enough to train on for years.

So the question is not which protocol is scientifically perfect. It is which protocol you can execute repeatably, in the same conditions, without blowing up. Here are the ones that work.

The 20-Minute Test

The classic. Warm up thoroughly (20-30 minutes with a few short openers, and many versions include a 5-minute all-out effort before the main block to burn off the anaerobic edge). Then ride 20 minutes as hard as you can sustain evenly. Multiply your average power by 0.95. That is your FTP.

The 0.95 factor exists because 20 minutes is shorter than the roughly hour-long effort FTP describes, so you can hold more power. For most trained riders the correction lands close. Riders with a big anaerobic engine can over-test on this protocol because they smuggle extra watts into 20 minutes that they could never hold for an hour. If your interval sessions at the resulting FTP feel impossible, that is the likely reason. Knock 2-3% off and see if the zones start making sense.

Pacing is where most people fail this test, and they fail it the same way every time: out too hot, dying at minute 8. The effort feels manageable for the first five minutes because your anaerobic system is covering the overdraft. Then the bill arrives. Power sags 30-40 watts, the last ten minutes become survival, and the average ends up lower than a patient ride would have produced.

The fix is a negative-split plan. Start at what you believe you can hold, or 5-10 watts below it. Hold that through minute 12. If you have something left at minute 15, spend it. The best 20-minute tests end with the final 3 minutes as the hardest of the ride. If minute 8 is your hardest minute, you paced it wrong, and the number is soft.

The Ramp Test

Start easy and increase power by a fixed step (commonly 20-25 watts per minute) until you cannot turn the pedals at the target. FTP is estimated as a percentage of your best 1-minute power at the end, usually around 75%.

The appeal is execution. There is no pacing to get wrong. You ride until you stop, and the protocol does the math. It takes about 25 minutes including warmup, it hurts for five of them, and it produces a number every time. For athletes who dread test day, or who keep botching the 20-minute pacing, the ramp test removes the failure mode.

The trade is accuracy at the edges of the physiology. The general consensus among coaches is that ramp tests tend to overestimate FTP for punchy riders with strong short-duration power, because the final minute leans on the anaerobic system, and tend to underestimate it for diesel-type riders who can grind at threshold all day but lack a sprint finish. If you are one of those diesels, your ramp result may sit 10-15 watts below what a longer test would show. Same rule as always: check the number against how training feels, and adjust.

2x8 Minutes

Two 8-minute all-out efforts with 10 minutes easy between them. Average the two, take roughly 90% of that average.

This protocol splits the difference. Shorter blocks are easier to pace than a continuous 20, and the second effort punishes anyone who went out too hard in the first, which self-corrects the pacing error the 20-minute test invites. It suits athletes newer to testing, and it fits into a shorter session. The correction factor is rougher than the 20-minute version, so treat the result as a starting point and expect to nudge it once real sessions confirm or deny it.

The Long Way: 40-60 Minute Efforts

The most honest test is the one that skips the correction factor. Ride 40-60 minutes at the highest power you can hold evenly, and the average is your FTP, near enough. No multiplier, no protocol bias.

Almost nobody does this, for good reasons. A true hour effort is brutal, it wrecks two or three days of training, and pacing it well is a skill in itself. But if you race 40k time trials, or you are a long-course triathlete who wants to know what an hour of steady output looks like from the inside, one of these per season teaches you things a 20-minute test cannot. Treat it as a race simulation that happens to produce a number.

Indoor or Outdoor: Pick One

Trainer power and road power are not the same number for most riders. Cooling is worse indoors, the fixed position removes the micro-freewheeling of the road, and motivation differs. It is common to test 5-15 watts lower on the trainer, though some riders go the other way.

The rule: test in the context you train in, and stay there. If your interval work happens on a smart trainer, test on the trainer, and do not import an outdoor FTP into indoor sessions. If you keep both contexts, keep two numbers. Comparing this month's indoor test to last month's outdoor test tells you nothing about fitness. Same protocol, same setting, same power meter, or the comparison is noise.

Which raises the power meter point. Pedals, crank, and trainer can disagree by 2-3% or more, all of them within spec. That gap is invisible in a single ride and decisive in a test-to-retest comparison. Calibrate before every test and use one power source as the source of truth.

How Often to Retest

Every 6-8 weeks, or at the end of a training block, whichever the plan dictates. Fitness moves slower than motivation, and testing more often than that measures your day-to-day freshness, not your threshold.

Retest under matched conditions: rested (two easy days prior), fed, same time of day if you can manage it, same protocol. A test ridden on tired legs is a wasted test. If the block was interrupted by illness or a two-week work trip, retest anyway. Riding a pre-illness FTP after a layoff turns every threshold session into an over-threshold session, and the normalized power and stress numbers on every ride will quietly lie to you until the anchor gets fixed.

What to Do With the Number

Set your zones and stop looking at it. Run the result through a power zones calculator and let the zones drive your sessions: zone 2 rides that stay easy enough to work, threshold intervals that sit where threshold sits, VO2 work that lands above it, not on it.

FTP is a means. The number itself is not the goal, and chasing it produces a familiar failure pattern: athletes who train for the test, over-perform the 20-minute protocol, set inflated zones, and then wonder why every prescribed session is a death march. Your FTP going up is a side effect of training well. It is not the training.

Also worth checking your power-to-weight ratio once the number settles, since w/kg predicts climbing performance better than raw watts.

Common Mistakes

Testing fatigued. The most common one. An FTP test after a hard weekend measures fatigue, not fitness. Two easy days before, minimum.

Going out too hot. Covered above. Minute 8 is where optimism goes to die. Negative-split the effort.

Comparing across platforms. A trainer-app ramp result versus a road 20-minute test versus a number your friend got on different pedals. None of these compare. One protocol, one setting, one power source, tracked over time.

Never retesting. An FTP from last October is a rumor. Zones drift with fitness in both directions, and detraining is the direction people refuse to test.

Testing weekly. The opposite error. Threshold moves over weeks, not days. Constant testing burns hard-session capacity that should be going into training.

Skipping calibration. A zero-offset takes ten seconds. A 3% drift in the meter takes months to notice.

Where the AI Coach Fits

This is one of the things an AI coach handles for cyclists without being asked. Movement Rebels schedules the retest when the block warrants it, rather than leaving it to memory. Since rides and power data flow in through the Garmin integration, the coach also reads the signal between tests: when your recent threshold sessions come in with lower heart rate at the same power, or you hold prescribed watts with room to spare, the post-ride debrief flags that FTP has likely moved, and the weekly adaptive plan adjusts zones instead of waiting for a formal test to catch up. Test days themselves get pushed to your Garmin as structured workouts, warmup and effort blocks pre-loaded.

You can also sanity-check any result against the FTP calculator before committing zones to it.

Pricing

Movement Rebels covers the complete picture: strength, endurance, hybrid, planning, AI coach, nutrition tracking, recovery tools, and native integrations with Garmin, Strava, and Apple Health on iOS. One app instead of five.

The 7-day free trial gives you the full coach, the adaptive plan, structured workouts pushed to your Garmin, and the post-ride analysis. No card required. After the trial, it is $20/month for unlimited coaching.