FTP, or functional threshold power, is the highest average power you can sustain for roughly an hour before fatigue forces you to slow. It sits close to your lactate threshold—the intensity where your body produces lactate faster than it can clear it—which is why coaches use it as a proxy for that physiological ceiling. In practice, if you're a trained amateur, you're probably looking at something more like 40–50 minutes at true FTP, not a full hour. Elite riders inch closer to 60. The "one hour" rule is a convention, not a universal law.
What FTP isn't: a perfect measure of fitness. It's a practical field metric, not a lab number. Research published in the Journal of Strength and Conditioning Research in 2023 confirmed that outdoor FTP tests produced significantly higher power values than both critical power and the 4 mmol/L lactate threshold measured in a controlled lab setting. That doesn't make FTP useless—it makes it a useful proxy that needs context. You shouldn't compare your FTP directly to another rider's without knowing how each of you tested, and you shouldn't treat a single number as the full portrait of your endurance engine. That said, for self-coached riders without regular lab access, it's often the most practical calibration tool available. From that reference point, interval targets, training zones, and volume thresholds can all be anchored to something real. If you haven't settled on a zone model yet, the training zones overview on this blog covers the main frameworks and how to choose one.
How to test it properly
The most common method is the 20-minute test: ride as hard as you can for 20 minutes on an indoor trainer or a steady, uninterrupted climb, then multiply the average power by 0.95. If you've been training for less than two years or are new to structured work, use 0.93 instead—the 5% reduction accounts for the pacing difference between 20 minutes and a true 60-minute maximal effort. Experienced riders can often sustain a higher fraction of their 20-minute power; less experienced ones can't pace it as well, which is why the fixed 0.95 multiplier slightly overestimates FTP for beginners.
The ramp test has become the default on platforms like Zwift and TrainerRoad because it's less psychologically brutal—you increment power by 20 watts each minute until you crack, and the software takes 75% of your best-minute average as FTP. It's reliable for most riders, but it has a known bias: it tends to favour athletes with stronger anaerobic systems, so pure endurance types can find it slightly underestimates their threshold. Neither protocol is universally better. What matters most is consistency—pick one method and stick with it every time you retest, so comparisons are meaningful.
A few practical details most guides skip: never test when you're carrying fatigue from a hard block. Post-rest-week testing, when you're genuinely fresh, gives you a far more accurate reading than mid-block testing does. And don't test more than once every six weeks during active training—FTP doesn't change week to week, but your form does, and a test done when you're fatigued will produce a number that's lower than your actual fitness. One more thing: a well-paced test should hurt considerably from around the eight-minute mark. If the last five minutes didn't feel like a genuine struggle, you left power on the table.
The training approaches that actually move your FTP
Three main stimulus types reliably raise FTP over a training block: sweet spot work, threshold intervals, and VO2max intervals. The first two are often conflated, and the confusion leads to blocks that are too hard to absorb but not hard enough to generate the right adaptation.
Sweet spot sits at roughly 88–93% of FTP. It's demanding enough to drive meaningful aerobic gains—raising mitochondrial density, improving fat oxidation, expanding your threshold bandwidth—without crushing your ability to recover and train again the next day. A classic sweet spot session of 2–3 sets of 15 minutes, with 5 minutes recovery between, delivers a lot of adaptation per unit of fatigue. For time-crunched riders, it's an efficient workhorse. The limitation is this: done exclusively and indefinitely, it stalls. Your body adapts to a specific stimulus. After 8–10 weeks of consistent sweet spot work, most riders need to either increase volume significantly or shift the intensity upward to keep the signal strong.
Threshold intervals run at 95–105% of FTP—at and just above the number you tested. The classic formats are 4 × 8 minutes or 2 × 20 minutes at 95–100%. These are harder to recover from than sweet spot, and pacing discipline matters in a way it doesn't at lower intensities. Grinding through the last interval at 86% because you started too hot turns what should have been a threshold stimulus into a badly executed sweet spot session that also beat you up. That's a common failure mode among self-coached riders. Going out slightly conservative and building into each interval is almost always the better strategy.
VO2max intervals—typically 3–5 minutes at 110–120% of FTP—work at the ceiling of your aerobic system and pull that ceiling upward over time. Raising VO2max raises the upper boundary of what your threshold can ultimately become, so neglecting this zone entirely puts a cap on long-term FTP development. These sessions don't need to dominate your plan, but one session every ten to fourteen days during a build phase compounds well with threshold and sweet spot work. Ignore them for too long and you'll find yourself hitting a plateau around the same FTP number, block after block.
What to do once you have a new number
Retest after a rest week, not before it. Your true fitness reveals itself when you're fresh, not mid-block. A post-recovery test that shows a 4-watt improvement is a cleaner signal than a fatigued test showing 8 watts, because the latter is partly measuring your ability to push through tiredness, not your actual adaptation. Once you have a confirmed new FTP, update your zones. Riding with outdated zones is one of the most reliable ways to accidentally undermine your training—what you think is threshold work slides into sweet spot territory, and your top-end sessions become genuine overreach. LeCoach recalculates all training zones automatically when you update your FTP, so every session stays anchored to your current fitness rather than where you were three months ago.
One last thing worth saying plainly: FTP is a measure of sustained flat-road aerobic output. It doesn't tell you how well you sprint, how you handle short punchy climbs, or how you hold up when pace is irregular and the road constantly disrupts your rhythm. It's an important number—arguably the most useful single metric in cycling training—but it's not the whole picture. Use it as a calibration tool, not a scoreboard.
Sources: Bok et al. (2023). "Functional threshold power field test exceeds laboratory performance in junior road cyclists." Journal of Strength and Conditioning Research / PMC.