What FTP means physiologically
Functional Threshold Power is the highest average power output a cyclist can sustain for about an hour without progressively fatiguing, a concept described by Hunter Allen and Andrew Coggan in Training and Racing with a Power Meter. It functions as an individual reference point: because riders vary enormously in absolute power capability, expressing a workout's target intensity as a percentage of a rider's own FTP allows training zones to be personalized rather than based on a fixed wattage that would mean very different things for different riders.
FTP is not a fixed number for life. It rises and falls as fitness changes, which is why structured power-based training programs periodically retest it, commonly every several weeks within a training block.
The 95%-of-20-minute-power test convention
Sustaining a genuinely maximal 60-minute effort is physically demanding and impractical to repeat often for testing purposes. The common field-test convention instead estimates FTP from a shorter, maximal 20-minute effort, discounted by 5% to approximate the somewhat lower power that can be sustained for a full hour: FTP (W) = 0.95 × 20-minute average power (W).
Worked example: a rider who averages 250 W for a maximal, evenly paced 20-minute effort has an estimated FTP of 250 × 0.95 ≈ 237.5 W. For a 75 kg rider, that is approximately 237.5 ÷ 75 ≈ 3.17 W/kg.
The 95% approximation works reasonably well for many riders but is not exact for everyone. Riders with strong anaerobic capacity may sustain a 20-minute effort at a higher relative intensity than their true one-hour threshold, which inflates the FTP estimate, while others pace a 20-minute test closer to their actual sustainable threshold. Pacing errors during the test -- starting too hard and fading, or holding back -- bias the estimate directly in either direction.
Coggan's seven-zone power training model
Once FTP is estimated, training intensities are commonly expressed as percentage bands of it, following Andrew Coggan's widely used seven-level power-training-zone model. The table below shows the published percentage ranges together with the resulting wattages for the 237.5 W FTP estimate from the worked example above.
| Zone | % of FTP | Watts (FTP = 237.5 W) | Physiological focus |
|---|---|---|---|
| Zone 1 — Active recovery | Below 55% | Below ≈131 W | Easy recovery riding |
| Zone 2 — Endurance | 56% – 75% | ≈133 – 178 W | Aerobic base training |
| Zone 3 — Tempo | 76% – 90% | ≈181 – 214 W | Moderate sustained effort |
| Zone 4 — Lactate threshold | 91% – 105% | ≈216 – 249 W | Sustainable-threshold intensity |
| Zone 5 — VO2 max | 106% – 120% | ≈252 – 285 W | Maximal aerobic power |
| Zone 6 — Anaerobic capacity | 121% – 150% | ≈287 – 356 W | Short, very high-intensity efforts |
| Zone 7 — Neuromuscular power | Above 150% | Above ≈356 W | Maximal sprint efforts |
Watts per kilogram: when it matters and when it doesn't
Watts per kilogram divides power output by rider body weight, and it is the standard normalization used in cycling because climbing speed on steep gradients is governed largely by power relative to total system weight. A physics-based model of cycling power -- validated against directly measured power in studies such as Martin and colleagues (1998) -- shows why: on a climb, a gravity term proportional to combined rider-and-bike mass dominates the power required, so a lighter rider needs less absolute power to climb at the same speed as a heavier one.
On flat roads, by contrast, speed is governed largely by absolute power relative to aerodynamic drag, since gravity plays little role when the road angle is near zero -- aerodynamic drag force grows with the square of airspeed, and the power needed to overcome it grows with the cube, regardless of rider weight. This is why a heavier but more aerodynamic or more powerful rider can hold a higher flat-road speed than a lighter rider with a lower FTP, even though the lighter rider might climb faster.
Because sustainable watts per kilogram varies enormously with training background, effort duration, age and other individual factors, no single number defines a 'good' FTP or W/kg value across all riders. Comparing an individual's own W/kg over time, at a consistent effort duration, is generally more informative than comparing against other riders.
Keeping the estimate useful
An FTP estimate from the 95%-of-20-minute convention is a practical training tool, not a laboratory measurement. It is most useful when the 20-minute test is performed with a proper warm-up and an evenly paced, genuinely maximal effort, and when it is retested periodically as fitness changes -- an FTP estimate from months ago can meaningfully understate or overstate current threshold power, shifting every training zone along with it.
Preguntas frecuentes
What is FTP in cycling?
FTP, or Functional Threshold Power, is the highest power output a cyclist can sustain in a quasi-steady physiological state for approximately one hour. It serves as the standard reference point for setting power-based training zones, a concept described by Hunter Allen and Andrew Coggan in Training and Racing with a Power Meter.
How is FTP calculated from a 20-minute test?
The common field-test convention estimates FTP as 95% of the average power sustained during a maximal, evenly paced 20-minute effort, since repeating a true 60-minute maximal test often is impractical. A 250 W average for 20 minutes gives an estimated FTP of about 237.5 W.
How accurate is the 95% FTP estimate?
It works reasonably well for many riders, but individual variation exists: riders with strong anaerobic capacity may hold a 20-minute effort at a relatively higher intensity than their true one-hour threshold, which can inflate the estimate, while others pace closer to their actual threshold. Periodic retesting helps keep the estimate current as fitness changes.
What are Coggan's power training zones?
Andrew Coggan's seven-level power-training-zone model expresses training intensities as percentage bands of FTP, from Zone 1 (active recovery, below 55% of FTP) to Zone 7 (neuromuscular power, above 150% of FTP), each targeting a different physiological training focus.
Why does watts per kilogram matter more on climbs than on flat roads?
On a climb, the power required is dominated by lifting the combined mass of rider and bike against gravity, so power relative to weight determines climbing speed. On flat roads, aerodynamic drag -- which depends on speed and frontal area rather than weight -- dominates instead, which is why watts per kilogram matters far less for flat-road performance than for climbing.
How often should FTP be retested?
FTP changes as fitness improves or declines, so many structured power-based training plans include periodic retesting, commonly every several weeks within a training block, to keep power zones aligned with current threshold capability.
Referencias
- Allen H, Coggan A, McGregor S. Training and Racing with a Power Meter, 3rd edition. VeloPress, 2019.
- Coggan A. Power training levels for cycling — the Coggan seven-zone power-training-zone model. TrainingPeaks.
- Martin JC, Milliken DL, Cobb JE, McFadden KL, Coggan AR. Validation of a mathematical model for road cycling power. Journal of Applied Biomechanics 1998; 14(3): 276–291.
- American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription, 11th edition. Wolters Kluwer, 2021.