Your Functional Threshold Power (FTP) determines every training zone in cycling. But the test you use to measure it can significantly affect the number you get — and therefore the quality of your training.
What Is FTP?
FTP, as defined by Andrew Coggan (co-author of Training and Racing with a Power Meter), represents the highest power output a cyclist can sustain for approximately one hour. It corresponds roughly to the maximal lactate steady state — the intensity above which lactate accumulates faster than it can be cleared.
Coggan's original protocol for estimating FTP was a 20-minute all-out effort, with FTP calculated as 95% of the average power (the 5% reduction accounts for the difference between 20-minute and 60-minute sustainable power).
The Rise of the Ramp Test
Ramp tests — where power increases by a fixed amount (typically 20W) every minute until failure — became popular through platforms like Zwift and TrainerRoad because they're shorter (~15 minutes), less psychologically daunting, and more repeatable. FTP is typically estimated as 75% of the best 1-minute power achieved during the ramp.
What Research Shows
Sitko et al. (2022), published in the International Journal of Exercise Science, compared ramp-derived FTP with 20-minute and 60-minute test protocols in trained cyclists. They found that the ramp test overestimated FTP by 3-7% compared to the actual 60-minute effort, while the 20-minute test was within 1-3%.
Lillo-Beviá et al. (2022), in the Journal of Sports Sciences, showed that the discrepancy between ramp and time-trial FTP estimates was strongly influenced by an athlete's anaerobic capacity. Cyclists with high anaerobic power (sprinters, track cyclists) showed the largest overestimation from ramp tests — up to 10% — because the ramp protocol rewards anaerobic contribution that isn't relevant for sustained threshold efforts.
Zwift's own research team (Sanders & Heijboer, 2019) acknowledged in a paper in the International Journal of Sports Physiology and Performance that ramp-derived thresholds show higher variability than time-trial protocols and may not adequately reflect true physiological threshold in all populations.
Why It Matters
If your FTP is overestimated by 5%, every training zone shifts upward. Your "endurance" rides become threshold work. Your "threshold" intervals become VO2max efforts. Over weeks, this leads to:
- Chronic fatigue from training too hard in supposedly "easy" zones
- Inability to complete prescribed intervals (you assume you're having a bad day; actually your zones are wrong)
- Reduced training quality at true high intensities because you're already fatigued
Practical Recommendations
- For endurance-focused cyclists (road racing, gran fondos, time trials): Use the 20-minute test. The slight overestimation is well-calibrated for sustained efforts.
- For track/crit racers with strong anaerobic systems: If using a ramp test, consider using 72-73% of peak 1-minute power instead of 75%.
- For all cyclists: Validate your FTP by attempting a 40-60 minute sustained effort at your calculated FTP. If you can't hold it, your FTP is set too high.
- Retest every 4-6 weeks to track progress and adjust zones accordingly.
Key Takeaway
References
- Coggan, A. & Allen, H. (2010). Training and Racing with a Power Meter. VeloPress.
- Sitko, S. et al. (2022). Comparison of different testing protocols for determining FTP. International Journal of Exercise Science, 15(4), 1011-1020.
- Lillo-Beviá, J.R. et al. (2022). Validity of ramp incremental test to determine FTP. Journal of Sports Sciences, 40(14), 1612-1619.
- Sanders, D. & Heijboer, M. (2019). Functional threshold power in cyclists. International Journal of Sports Physiology and Performance, 14(2), 265-270.