Introduction
Functional Threshold Power (FTP) is the cornerstone metric for power-based training — the best single-number estimate of the highest power you can sustain for roughly one hour. For intermediate cyclists with a power meter, accurate FTP measurement unlocks meaningful training zones, objective progress tracking, and smarter sessions. This FTP test cycling guide explains common protocols (20-minute, ramp, 2x8, critical power), how to prepare and execute them, and how to validate results so your training stays honest and productive.
Understanding Functional Threshold Power
FTP is conceptually close to your lactate threshold or the highest steady-state power before fatigue accelerates. Practically, FTP is used to set zones (sweet spot, tempo, threshold, VO2max) and to prescribe interval intensity.
Common testing approaches:
- 20 minute FTP test: One of the most popular field tests. Complete a maximal 20-minute time trial and multiply your average power by 0.95 to estimate your one-hour FTP.
- Ramp test FTP: Power increases in fixed steps (typically 20–30 W every minute) until you can no longer continue. FTP is estimated from the maximal one-minute power reached. It's shorter and less mentally grueling but tends to give slightly higher FTP estimates for some riders.
- 2x8-minute (or 2x10) test: Two hard, steady efforts separated by a short recovery. Average of the efforts converted with a smaller correction factor can provide a robust FTP estimate with better pacing control than a single 20-minute effort.
- Critical power (CP) modelling: Uses multiple all-out efforts of varying duration (e.g., 3, 5, 12 minutes) to fit a CP curve. CP is a model-derived sustainable power and can be a closer scientific analog to FTP when enough data are available.
Each method has trade-offs in duration, rider comfort, and physiological assumptions. The key takeaway: protocols differ, but consistent preparation and validation are what make your FTP useful.
Preparing for Your FTP Test
Power Meter Calibration
Accurate power is non-negotiable. Before any FTP test, perform these checks:
- Follow the manufacturer's zero-offset or calibration routine (esp. for crank/left-right and pedal meters).
- Update firmware and confirm the device reports stable battery voltage.
- Do a warm-up offset check in the test environment — temperature shifts between storage and riding can change readings.
Poor calibration biases FTP and will skew training zones. See N+One’s power meter calibration guide for step-by-step instructions on keeping your meter honest.
Testing Environment
- Indoor trainers reduce external variables (wind, traffic, gradient) and are ideal for repeatable FTP test cycling. Use a fan, hydration, and simulated race-motivation (music, trainer apps) to help effort.
- Outdoor tests are valid too but require a steady course, minimal stopping, and consistent conditions to be repeatable.
Physical and Mental Preparation
- Avoid high training load 48 hours before the test — aim for a light spin and full rest the day before.
- Hydrate and eat a carbohydrate-rich meal 2–3 hours prior. Consider a small carbohydrate snack 30–60 minutes before testing if you typically benefit from it.
- Warm up 15–30 minutes with progressive efforts and include a few short, race-pace bursts to prime the neuromuscular system.
- Plan pacing and mental checkpoints. Even pacing wins most 20-minute tests — resist surging early.
Executing FTP Test Protocols
20 Minute FTP Test (Protocol)
- Warm up 20–30 minutes with progressive efforts and 3–5 short high-cadence or 1-minute hard efforts.
- Start the 20-minute maximal effort; aim to hold a steady power slightly below your estimated capacity for the first 5 minutes, then maintain the highest sustainable effort.
- Cool down 10–15 minutes.
- Calculate FTP = average 20-minute power × 0.95.
Pros: well-understood, good pacing practice. Cons: mentally and physiologically demanding; correction factor assumes ability to sustain longer efforts.
Ramp Test FTP (Protocol)
- Warm up thoroughly (20–30 minutes) including short sprints.
- Start the ramp: every minute (or 2 minutes) increase power by a fixed amount until failure.
- FTP is estimated from the maximal completed stage (varies by protocol; some apps use % of best minute power).
Pros: shorter, easier to execute indoors; cons: can overestimate FTP for some athletes and is sensitive to step size and cadence.
2x8 or 2x10 Protocol
- After a proper warm-up, perform two maximal steady efforts (8–10 minutes each) with a 10–15 minute easy spin between them.
- Take the average of the two efforts and apply a small correction (often 0.93–0.96 depending on protocol).
This approach reduces the impact of pacing errors and gives a more reliable physiological signal for threshold power.
Critical Power Testing
Collect multiple maximal efforts across durations (e.g., 3, 5, and 12 minutes) and fit a CP model. CP requires data handling but yields a curve that characterizes both sustainable power and anaerobic work capacity (W'). Advanced riders and coaches use CP for nuanced training prescriptions.
FTP Validation and When to Test FTP
FTP Validation
An FTP number is only useful if it matches real-world performance. Validate by:
- Comparing training session success: are prescribed intervals at target intensities achievable? If long threshold intervals feel too hard or too easy, reassess FTP.
- Checking race or time-trial performances: sustained efforts in competition are the strongest validation.
- Monitoring trends: rising CTL (chronic training load) with improved normalized power for set race distances suggests FTP is moving.
Frequent testing without validation wastes energy. Real-world performance often provides better FTP validation than repeated lab-style tests.
When to Test FTP
- Retest every 4–8 weeks during focused build phases or after a block of structured training. This frequency balances sensitivity to adaptation and test fatigue.
- Test less during maintenance phases; only retest if workouts consistently miss targets or life changes (illness, travel) suggest altered capacity.
Common Pitfalls and Practical Tips
- Don’t test when ill, sleep-deprived, or under-fueled — results will underrepresent capacity.
- Be consistent: same protocol, same environment, same warm-up and nutrition for repeat tests.
- Know the indoor-outdoor difference: many riders produce slightly different numbers indoors vs outdoors; choose one method and use it consistently.
Conclusion
FTP test cycling is an essential skill for power-based training. While multiple protocols exist — 20-minute, ramp, 2x8, and critical power modelling — the accuracy of your functional threshold power depends on consistent preparation, precise power meter calibration, and validation against real-world performance. Retest on a 4–8 week cadence during build phases, but let training data and races confirm whether your FTP truly represents your capacity. With disciplined testing, sensible validation, and consistent application, FTP becomes a trustworthy anchor for smarter workouts and measurable progress.
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