FTP Explained: What Functional Threshold Power Means and How to Test It Right
FTP is the most over-tested, most misunderstood number in cycling. Here's what it actually represents, the three testing protocols that work, and how to use it to train.
Functional Threshold Power — FTP — is the highest average power you can sustain for roughly one hour. It's the anchor of every modern power-based training plan: every cycling zone, every workout target, every season-over-season comparison flows from this one number.
Yet most cyclists carry an FTP they over-estimated in a fresh-legs 20-minute test, then spend a season failing workouts and blaming the trainer. Honest FTP, tested well, is the single best lever you have.
What FTP actually represents physiologically
FTP is a proxy for the maximal lactate steady state (MLSS) — the highest intensity at which lactate production and clearance balance. Above FTP, lactate accumulates exponentially and the clock starts ticking. Below it, you can ride for hours. The closer your prescribed FTP is to your true MLSS, the more useful your training zones become.
Three FTP tests that actually work
1. The Ramp Test (20–25 minutes total)
Power increases by a fixed wattage each minute until failure. FTP ≈ 75% of the highest one-minute power you sustained. Low fatigue cost, easy to repeat monthly, slightly under-predicts FTP for diesel engines and over-predicts for fast-twitch riders.
2. The 20-Minute Test
After a structured warm-up and a 5-minute opener, ride 20 minutes maximal. FTP = 95% of 20-minute average power. Most accurate of the three for trained cyclists; brutal mentally and physically.
3. The 8-Minute Test
Two 8-minute maximal efforts with 10 minutes recovery. FTP ≈ 90% of the higher 8-minute average. Useful for crit racers and shorter-event athletes; tends to inflate FTP for diesel engines.
An FTP that's 10 watts too high turns every sweet-spot workout into an over-threshold workout. Three weeks later you're flat, defeated, and convinced you've stopped progressing.
Coggan power zones from FTP
- Zone 1 — Active Recovery: <55% FTP
- Zone 2 — Endurance: 56–75% FTP
- Zone 3 — Tempo: 76–90% FTP
- Zone 4 — Lactate Threshold: 91–105% FTP
- Zone 5 — VO2max: 106–120% FTP
- Zone 6 — Anaerobic: 121–150% FTP
How often to re-test
Every 4–6 weeks in build phase, once at the start and once mid-block in a race build. If two consecutive sweet-spot sessions feel suddenly easy, bump FTP up by 2–3% and verify. If you fail two threshold workouts in a row when fresh, drop FTP by 3–5%.
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Book a discovery callEndurance coach since 2015. RRCA-certified, USAT Level II, TrainingPeaks Level 2. 12× Boston Marathon qualifier. Based in Fenway, Boston — coaching athletes worldwide in English, Portuguese, and Spanish.
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