Training zones

Why FTP isn't the whole story

Functional threshold power (FTP) is the highest power you can sustain for roughly an hour. It is a useful performance number for setting zones and tracking progress, but it describes what you can do, not why. Two riders with the same FTP can get there with very different physiology, hold up very differently over hours, and need different training.

Use FTP as a shared reference point, then look past it: at what sits underneath it, and at what happens to you late in long sessions.

By Nick Buckley-Mills, Team GBR age-group triathlete Reviewed 2 November 2026 12 min read

At a glance

What FTP is	A performance measure: roughly an hour's best sustainable power, usually estimated from a shorter test
What it's good for	A common reference for zones, sessions and progress that every device and coach understands
What it doesn't tell you	How big your aerobic engine is, how you produce the power, or how well you hold it after hours of work
How close it is to your threshold	Close on average in studies, but often tens of watts off for an individual
What else describes you	VO2max, your steady-state ceiling (MLSS or critical power), lactate profile, efficiency and durability
How to use it	Keep it as the reference, treat zones built from it as starting points, and check them against how you respond

What is FTP?

FTP is your best average power for about an hour, measured in watts. Hunter Allen and Andrew Coggan popularised it as a practical stand-in for threshold: easy to test with a power meter, easy to share, and the anchor for training zones and for training-load scores such as TSS. Coggan himself has long looked beyond the single number, with the power profile and power-duration models that show strengths and limiters across durations.

Few athletes ride flat out for an hour to find it. Most use a shorter test and a formula, such as 95% of a 20-minute all-out effort, or a ramp test. Runners and swimmers have equivalents, threshold pace and CSS (critical swim speed), and the points below apply to them too.

Its simplicity is why it caught on. You can compare one test with the next, and every platform, device and coach understands the number. See how training zones work for how it becomes a set of zones.

Is FTP your physiological threshold?

On average it lands close to one, but for an individual it can be well off. Several studies have compared FTP with lab measures of threshold in trained cyclists:

Close on average, wide for individuals. FTP from a 20-minute test matched a lactate-based threshold on average, with large correlations, but the gap for individual riders was wide enough that the authors advised against using the two interchangeably.
Tens of watts either way. In another group of cyclists, FTP sat close to the power at a fixed blood lactate of 4 mmol/L on average, yet for individuals it could be roughly 45 W lower or 50 W higher.
Not an hour, and not a boundary. Riders held their FTP for about 51 minutes in the first of those studies, and about 34 minutes in a later one: often less than the hour many people assume. In the later study, by Wong and colleagues, oxygen uptake still levelled off 15 W above FTP, which suggests FTP doesn't mark the line between hard-but-steady and unsustainable effort.

Most of these studies tested the 20-minute shortcut rather than FTP as Coggan defines it: the highest power you can hold in a quasi-steady state, which he expects to last roughly 30 to 70 minutes rather than exactly an hour.

None of this makes FTP useless. It means FTP is a good estimate of where your threshold is, not a measurement of it. The lactate thresholds guide explains what a lab test measures instead.

Why percentages of one number mislead

Training by percentages assumes everyone's physiology sits in the same place relative to that one number. It doesn't. In a study of 100 men and women, the first lactate threshold fell anywhere between 45% and 74% of VO2max, and the maximal lactate steady state between 69% and 96%. The same percentage put different people in different intensity domains: easy for one, hard and unsustainable for another.

That study used percentages of VO2max and maximum heart rate, but the problem applies to FTP too, though less near threshold, because FTP sits close to one. It's largest for zones far from it, especially easy riding around the first threshold. A session written as "3 x 15 minutes at 95% of FTP" is steady threshold work for one rider and close to their limit for another. So zone edges are conventions, and the same session can feel very different to two athletes with the same number.

Sport scientists separate the work you do, called external load, from the stress it puts on you, called internal load. The same session can create very different internal load in two athletes, or in one athlete on two different days.

What else describes an athlete?

Endurance performance has long been explained by three things: how much oxygen you can use, how much of it you can sustain, and how efficiently you turn it into speed. FTP is the result of all three. Looking at them separately shows why two athletes reach the same number differently.

VO2max: the size of your aerobic engine, the most oxygen your body can take up and use.
Your steady-state ceiling: the highest effort at which your body can still settle, measured as the maximal lactate steady state (MLSS) or critical power. Some physiologists argue critical power marks this boundary more accurately than MLSS.
Your lactate profile: where your turn points sit and how quickly lactate builds as effort rises. See lactate thresholds.
Glycolytic capacity (VLamax): how fast you can produce energy from carbohydrate without oxygen. In the model it comes from, a high value helps sprints and short efforts but can lower the power you can hold for long, steady events. It's hard to measure, and estimates depend on the test and the model behind them, so treat any single figure with caution.
Efficiency or economy: how much power or speed you get for the oxygen you use.
Durability: how much of the above you lose after hours of accumulated work. A fresh test, including an FTP test, can't show it, yet in long-course racing it decides the back half of the bike and the run off it. It depends on more than training: in one small study, taking carbohydrate during a long ride roughly halved the drop in the power riders could hold at the first threshold, and heat makes the same work harder. And it can be trained: in a ten-week study of previously inactive and recreationally active adults, both low- and high-intensity training reduced the strain of a three-hour ride.

In a recent note, coach Iñaki de la Parra describes FTP as "a performance metric, not a physiological diagnosis." It shows what you can produce, not why. His answer is to measure the physiology first, with the maximal lactate steady state as the reference point, and prescribe from that. He also separates stamina, how long you can hold an effort from fresh, from durability, how much you lose after hours of work.

Same FTP, different athletes

Here are two illustrative riders with the same FTP. They're invented to show the idea, not taken from a study.

	Rider A	Rider B
How they reach it	A big aerobic engine, but a high glycolytic rate, so lactate builds early	A smaller engine, but able to sustain a high share of it
Strengths	Strong over 1 to 5 minutes, good on short climbs	Steady for long periods, holds power late in long rides
Likely limiter	Fades in long events; threshold sits low relative to the engine	A low ceiling: little room above threshold
What might help most	Volume and threshold work to raise the steady-state ceiling, and long rides that build durability	VO2max work to raise the ceiling the threshold sits under

Rider A, freshRider A, after hours of workRider B, freshRider B, after hours of work

Illustrative shapes, not data. Both riders share an FTP. Rider A is stronger over short efforts; Rider B keeps more of their power after hours of work. The curves show what each rider can do; the physiology underneath explains why, which a power file alone can't show.

Give both the same plan built on percentages of that FTP and at least one of them will be training the wrong thing.

Even identical training doesn't produce identical results. In studies where everyone follows the same programme, some people improve a lot and others barely change. Your own record of how you respond is a better guide than any average.

What no sensor sees

Some of the biggest reasons training stalls never show up in a power file. Life stress, poor sleep, under-fuelling, mood and motivation all change how you respond to the same session, and no FTP, heart rate or device score captures them on its own.

There's research behind this. A systematic review found that athletes' own ratings of mood, stress, fatigue and recovery tracked changes in training more consistently than common objective measures such as heart rate and blood markers.

A short daily check-in is enough: sleep, fatigue, soreness, stress and mood, each on a simple scale. Sport scientists have used five-item questionnaires like this for years. Watch each item's trend over a week rather than adding them into one score. If your mood has dropped three days running, that's worth knowing, and a single total can hide it.

De la Parra makes the same case about readiness scores in a longer piece: the underlying data can be useful, but readiness is a decision for the athlete and coach, made from how you feel and what the data shows together. When the two agree, act on it. When they disagree, find out why before you decide.

How to use FTP without being ruled by it

Keep it as your reference. Test the same way each time, so changes reflect you rather than the protocol.
Treat zones as starting points. If a zone consistently feels too easy or too hard, or your heart rate disagrees with the power for weeks, trust the pattern and adjust.
Look at your power profile. Your best 5 seconds, 1 minute, 5 minutes and 20 minutes show where you're strong and where you're limited, which a single number hides.
Watch what happens late in long sessions. Compare your power and heart rate in the last hour of a long ride with the first. If one drifts away from the other, that tells you about your durability.
Test in a lab if you want precision. A lactate or VO2max test shows what sits under your FTP. Repeat it with the same protocol so the results are comparable.
Train what limits you. Raising FTP is a fine goal, but how you get there should depend on what's holding it back.

Treat each block as a test

Most training blocks are judged by feel at the end. A better habit is to treat each one as a small test.

Pick one objective tied to your limiter, such as holding power later in long rides.
Write down what you expect to change, and by how much, before you start. Don't edit it later.
Measure it the same way before and after.
Know your normal range. Results vary from day to day, so a small change may be noise rather than progress.
Review honestly, including what else happened: illness, heat, a hard month at work.

Over a season, those reviews tell you more about how you respond than any single test.

Keep a record of the why

Your files record what you did. They don't record why you changed a session, what you were worried about, or what else was going on that week. A line each time you make a decision, and a note later on how it turned out, will tell you more over a season than the files alone.

Common questions

Is FTP the same as lactate threshold?

Not exactly. FTP is a performance test of roughly an hour's sustainable power; lactate thresholds are turn points on your lactate curve. In studies of trained cyclists they land close together on average, but for an individual FTP can sit tens of watts above or below a lab threshold.

Can you really hold FTP for an hour?

Not always, and it isn't meant to be exact. Coggan expects roughly 30 to 70 minutes. In two studies of the 20-minute estimate, trained cyclists held it for about 34 and 51 minutes on average, with wide variation between riders. Treat FTP as an estimate of threshold power, not a promise about duration.

Is a 20-minute FTP test accurate?

It's a reasonable estimate and, done the same way each time, a good way to track change. The 95% factor is an average, though, so your true sustainable power may be a little higher or lower. Pacing, motivation and freshness on the day also move the result.

Should I stop using FTP?

No. It's a useful, shared reference and every device understands it. Use it to set starting zones and to track progress, and add other information alongside it: your power profile, how sessions feel, how heart rate responds, and what happens late in long sessions.

What is VLamax, and do I need to know mine?

VLamax is an estimate of how fast you can produce energy from carbohydrate without oxygen, from a model of energy metabolism developed in Cologne in the 1970s and 1980s. It's hard to measure, and figures depend on the test and model used. Most athletes can train well without it; it's one input among many.

Does this apply to running and swimming?

Yes. Threshold pace and CSS are the running and swimming equivalents of FTP, and they share the same strengths and limits: useful references, but estimates of your physiology rather than measurements of it.

Sources

Allen H, Coggan AR, McGregor S. Training and Racing with a Power Meter, 3rd edition. VeloPress, 2019.
Borszcz FK, Tramontin AF, Bossi AH, Carminatti LJ, Costa VP. Functional threshold power in cyclists: validity of the concept and physiological responses. International Journal of Sports Medicine. 2018;39(10):737–742.
Jeffries O, Simmons R, Patterson SD, Waldron M. Functional threshold power is not equivalent to lactate parameters in trained cyclists. Journal of Strength and Conditioning Research. 2021;35(10):2790–2794.
Wong S, Burnley M, Mauger A, Sun F, Hopker J. Functional threshold power is not a valid marker of the maximal metabolic steady state. Journal of Sports Sciences. 2022;40(23):2578–2584.
Iannetta D, Inglis EC, Mattu AT, Fontana FY, Pogliaghi S, Keir DA, Murias JM. A critical evaluation of current methods for exercise prescription in women and men. Medicine & Science in Sports & Exercise. 2020;52(2):466–473.
Joyner MJ, Coyle EF. Endurance exercise performance: the physiology of champions. The Journal of Physiology. 2008;586(1):35–44.
Jones AM, Burnley M, Black MI, Poole DC, Vanhatalo A. The maximal metabolic steady state: redefining the "gold standard". Physiological Reports. 2019;7(10):e14098.
Wackerhage H, Gehlert S, Schulz H, Weber S, Ring-Dimitriou S, Heine O. Lactate thresholds and the simulation of human energy metabolism: contributions by the Cologne Sports Medicine Group in the 1970s and 1980s. Frontiers in Physiology. 2022;13:899670.
Maunder E, Seiler S, Mildenhall MJ, Kilding AE, Plews DJ. The importance of "durability" in the physiological profiling of endurance athletes. Sports Medicine. 2021;51(8):1619–1628.
Dudley-Rode H, Zinn C, Plews DJ, Charoensap T, Maunder E. Carbohydrate ingestion during prolonged exercise blunts the reduction in power output at the moderate-to-heavy intensity transition. European Journal of Applied Physiology. 2025;125(5):1349–1359.
Matomäki P, Heinonen OJ, Nummela A, Laukkanen J, Auvinen E-P, Pirkola L, Kyröläinen H. Durability is improved by both low and high intensity endurance training. Frontiers in Physiology. 2023;14:1128111.
Impellizzeri FM, Marcora SM, Coutts AJ. Internal and external training load: 15 years on. International Journal of Sports Physiology and Performance. 2019;14(2):270–273.
Mann TN, Lamberts RP, Lambert MI. High responders and low responders: factors associated with individual variation in response to standardized training. Sports Medicine. 2014;44(8):1113–1124.
Saw AE, Main LC, Gastin PB. Monitoring the athlete training response: subjective self-reported measures trump commonly used objective measures: a systematic review. British Journal of Sports Medicine. 2016;50(5):281–291.
McLean BD, Coutts AJ, Kelly V, McGuigan MR, Cormack SJ. Neuromuscular, endocrine, and perceptual fatigue responses during different length between-match microcycles in professional rugby league players. International Journal of Sports Physiology and Performance. 2010;5(3):367–383.
Hopkins WG. Measures of reliability in sports medicine and science. Sports Medicine. 2000;30(1):1–15.
Jamnick NA, Pettitt RW, Granata C, Pyne DB, Bishop DJ. An examination and critique of current methods to determine exercise intensity. Sports Medicine. 2020;50:1729–1756.
de la Parra I. Note on FTP and physiology-first prescription. Substack, 26 October 2026.
de la Parra I. The readiness score is bullshit, the data isn't. Substack, 30 September 2026.