What Is FTP in Cycling? Meaning, Tests and How It's Calculated

James. Hi, and welcome to the WattPlan Podcast. I'm James. When I'm not juggling family life, the day job and the occasional podium, I'm building WattPlan and reading sports science papers I really should have put down hours ago. This week it's the number every rider quotes and half of us quietly doubt. What actually is FTP, and is your test telling you the truth? Lyra's here, our AI research voice, and every study she mentions is linked in the show notes.

Lyra. Ha, the number everyone argues about at the café stop. Straight answer first. FTP, Functional Threshold Power, is the highest average power you can hold for about an hour. Most riders don't ride the hour. They take 95 percent of their best 20 minutes instead. And it matters more than people think, because your training zones are set as percentages of it. Get FTP wrong and every interval is either too easy or too hard.

James. Right, so it's the foundation for everything else. Why an hour, though? Where does that come from?

Lyra. Researchers define it as the average power from a 60 minute time trial. Every other test is a shortcut to that hour. It's measured in watts, and if you divide it by your weight in kilos you get watts per kilo, which is what decides how you climb. A rider on 250 watts who weighs 75 kilos is at about 3.3 watts per kilo at threshold.

James. And nobody wants to ride a flat out hour on the turbo. So the 20 minute test. How good is it, really?

Lyra. It's the test with the best evidence, and we looked at three studies for this episode. The first is MacInnis and colleagues, in the International Journal of Sports Physiology and Performance, 2019. Eight trained male cyclists rode two 20 minute tests and one full hour. The two 20 minute tests came out at 342 and 344 watts, so it's very repeatable. And the 20 minute result was strongly linked to what they held for the hour. [1]

James. So 95 percent of 342. That's about 325 for the hour?

Lyra. That's what the convention would say. Here's the catch. Those riders actually held 309 watts for the hour. That's about 90 percent of their 20 minute power, not 95. So the test predicted the hour well, but the multiplier isn't fixed. For some riders 95 percent fits nicely, and for others it flatters them.

James. Hang on. So the number I've been training off for years might be a bit generous?

Lyra. It might be, and the second study points the same way. Inglis and colleagues, same journal, 2020. Eighteen participants, twelve men and six women, did a 20 minute test plus two or three constant power rides to find their maximal lactate steady state. That's the highest power where blood lactate stays level instead of climbing. It came out at about 93 percent of their FTP estimate. [2]

James. So riding at my FTP for a whole hour is harder than the name suggests.

Lyra. Exactly that. Which brings us to the study I like most, because it answers the thing every rider wonders. How long can I actually hold this number? Sitko and colleagues, in the Journal of Science and Medicine in Sport in 2022, took road cyclists' FTP from the 20 minute test and had them ride at it to exhaustion. They grouped the riders into four levels by VO2max, the most oxygen you can use in a minute. [3]

James. Go on then. How long did they last?

Lyra. Recreationally trained riders held it for a median of 35 minutes. Trained riders, 42. Well-trained, 47. Professionals, 51. So for most amateurs, about an hour overstates it. A newer rider's tested FTP is closer to a 35 minute effort, and the gap closes with years of training.

James. Oh, that's genuinely reassuring. I always assumed I was just soft for not lasting the hour.

Lyra. You're not soft, you're normal. Even the professionals in that study came up short of an hour. The name promises more than the test delivers, and that's fine, as long as you know it.

James. Okay, but what about the ramp test? It's shorter, it hurts for less time, and surely a test the trainer paces for me is more accurate than me guessing?

Lyra. Shorter, yes, and no pacing, because the trainer sets every step. But the sum takes 75 percent of your best minute at the end, and that minute has a lot of anaerobic work in it. So it rewards riders with a big kick and short-changes steady diesel types. We haven't found a peer-reviewed validation of that 75 percent. Our view at WattPlan is that the 20 minute test is the better default if you can pace an even effort, and the ramp suits a first test, when you've no idea where to start.

James. I'm a diesel, so that explains a lot. What about ERG mode, though? I'd love the trainer to just hold me there.

Lyra. That's the trap. In ERG mode the trainer holds the wattage you typed in, so a 20 minute test in ERG measures your guess, not your legs. You have to set the power yourself. In WattPlan's 20 minute test the effort block is a free ride, a flat road simulation where you choose the gears.

James. So talk me through doing it properly. What does a good test day look like?

Lyra. Test after an easy day, at your usual training time, with your usual fan and fuelling. Use the same bike and power source every time, because a smart trainer and a pedal power meter can read differently, and a change of device looks like a change of fitness. Warm up properly. Then start the 20 minutes at a number you believe you can hold, and only build in the last five minutes. The average is what counts, so a heroic first five minutes just costs you.

James. Love it. Let's split it out by who's listening. If you're new to this, what do you actually do with all that?

Lyra. If you're new to structured training, don't worry about the decimals. Do one test, and a ramp is fine for a first go, then set your zones from it. After that, listen to your sessions. If threshold intervals keep falling apart, or sweet spot feels like tempo, the number is wrong, and that's your cue to retest.

James. And if you train with power already?

Lyra. Then know that WattPlan works your test out at 95 percent. If threshold work keeps failing after a test, your own number may sit nearer 90 percent, so set your FTP a few percent lower yourself in Metrics. WattPlan also watches your rides. It takes your best 20 minutes from a ride recorded in the app, multiplies by 0.95, and only offers a new FTP when it's at least 3 percent above your current one. It never changes it on its own. You choose whether to update it or keep the current one.

James. And if you race, or you're pacing a big event?

Lyra. If you race, an inflated FTP gets expensive, because it sets your pacing too. A number that's a few percent high paces the whole day too hot, and you pay for it late on. Retest when your sessions start feeling easier than they should. A plan built round an event doesn't include a test, so ask the Coach to put one in. And here's a twist from that Inglis study. Ten riders repeated everything after seven months of training. Their lactate steady state rose by 12 watts, and their 20 minute FTP estimate didn't move. [2]

James. Wait, really? So my test can say flat when I've actually got fitter?

Lyra. It can. The test is a blunt instrument. Between tests, the best 20 minutes of your hard rides will often flag a rise before a formal test does.

James. Everyone wants to know this next one. What's a good FTP? Where do I stand?

Lyra. Honest answer, there's no peer-reviewed table of FTP by level for amateur riders, and we won't invent one. The papers that classify riders use VO2max per kilo and peak power from a lab test, which is always higher than what you can hold for an hour. So a good FTP is one that's honest and rising over the season. Watts per kilo is the fair way to compare yourself with last year, or with that friend who climbs better than you.

James. So where does the evidence run out?

Lyra. Quite quickly. The 20 minute studies are small and mostly men, eight riders in MacInnis, and eighteen in Inglis, of whom six were women. The 95 percent is a convention that fits some riders and not others. And nobody has published what FTP per kilo amateur riders actually have. So treat your FTP as a working estimate, and let your sessions tell you when it's drifted.

James. Right, homework. What do I do this week?

Lyra. Three things. One, if your threshold sessions have started to feel easy, plan a 20 minute test after an easy day, or ask the Coach to put one in your plan. Two, ride it out of ERG, starting at a number you can hold and building only at the end. Three, after your next threshold session, ask yourself whether it actually felt like threshold. If it didn't, your number needs moving.

James. So in my words. Test fresh, pace it myself, don't trust the 95 percent blindly, and let my sessions tell me when the number's off.

Lyra. That's it, you've got it. And if one line sticks, FTP is an estimate of an hour most of us can't actually ride. It's a tool for setting your zones, not a score to defend.

Lyra. The full article and every study we mentioned are on the WattPlan blog, linked in the show notes.

James. And if you want a plan that's built around the time you've actually got, that's what WattPlan does. Thanks for listening.

Voices produced with ElevenLabs. James's voice is a clone of his own, Lyra is an AI voice, and James reviews every episode.