FTP and power zones: what they measure and how far to trust them
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What FTP measures
FTP stands for Functional Threshold Power: the highest power you can sustain steadily for about an hour. The concept was popularised by Hunter Allen and Andrew Coggan, who also proposed training zones as percentages of FTP.1
Physiologically, the limit that matters is the maximal metabolic steady state: the highest intensity at which lactate and oxygen uptake stay stable. Scientists measure it with critical power or lactate tests.2 FTP is a practical way to get close to that value without a lab., but it does not measure it.
Studies of the 20-minute test are few and mostly on trained male cyclists.5 The test is repeatable: in 19 highly trained athletes two tests gave similar results (difference between −17 and +13 W).3 But repeatable does not mean exact: in 18 well-trained people, power at maximal lactate steady state (MLSS) was on average 88.5% of 20-minute FTP and 93% of the 95%-adjusted FTP, so the 95% overestimated it; in 23 cyclists the 95% of 20 minutes was close to individual threshold on average, but individuals differed by up to ±40–60 W.46 These are small samples.
The 20-minute test
- Warm up for 15–20 minutes with a couple of short efforts.
- 5 minutes hard, then 10 minutes easy, to use up your anaerobic reserve.
- 20 minutes at the highest average power you can hold, starting controlled.
- Estimated FTP = 20-minute average power × 0.95.
The 0.95 factor is a convention: it gives different results from person to person and in some studies overestimates threshold. Treat it as a starting point.
The zones, simplified
| Zone | % FTP | Use |
|---|---|---|
| Recovery | below 55% | Easy recovery rides |
| Endurance | 56–75% | The base: long, easy rides |
| Tempo | 76–90% | Sustained pace, in measured doses |
| Threshold | 91–105% | 8–20 minute blocks |
| VO₂max | 106–120% | 3–5 minute intervals |
The zones and retest interval are the Allen and Coggan convention, not results of controlled studies.
Repeat the test every 6–8 weeks, or when your zones clearly feel too easy or too hard.
How we reviewed it
Document review of the sources: validation studies on small samples of trained cyclists and reference texts on zones.
Limits. Few studies, small samples, almost only trained and mostly male cyclists. The 95% of the 20-minute test can overestimate threshold and differ by 40-60 W between people.
Related tool: Wolf Engine, power zones.
Sources
- Allen, Coggan, McGregor. Training and Racing with a Power Meter. VeloPress, 3rd edition 2019.
- Jones, Burnley, Black, Poole, Vanhatalo. The maximal metabolic steady state: redefining the 'gold standard'. Physiological Reports, 2019. DOI
- Reliability of the FTP test in 19 highly trained athletes. PMC
- Inglis, Iannetta, Passfield. MLSS versus 20-minute FTP in well-trained people (18 participants), 2019. Europe PMC
- Scoping review of the 20-minute FTP test (15 studies). PubMed
- Borszcz and colleagues. Functional Threshold Power in Cyclists: Validity of the Concept and Physiological Responses. International Journal of Sports Medicine, 2018. PubMed
Sources rechecked on 26 October 2026.