Yes, you can keep your FTP current without regular test days. Your best efforts from normal training contain much of the same information as a formal test, and research shows threshold estimates built from field data can be valid. The catch is knowing when that data reflects a true maximal effort and when it doesn’t.
Why a stale FTP holds you back
Every power target in a structured plan is a percentage of your FTP. If you’ve gotten fitter since your last test, your FTP is too low, and your threshold and Sweet Spot intervals are easier than they should be. You’re doing the work without getting the full stimulus.
If your FTP is too high, the opposite happens. Intervals feel impossible, you fail workouts, and fatigue builds without a matching gain in fitness. Either way, the plan stops matching your body.
The traditional fix is to retest at the start of each training block. That works, but it costs a training day, takes motivation, and leaves your FTP frozen between tests while your fitness keeps changing.
A test can also miss real change. In one study of well-trained cyclists, lab-measured maximal lactate steady state rose by 12 watts over seven months of training, while 20-minute FTP didn’t change significantly (Inglis et al., 2020).
How FTP can be estimated from ride data
The power-duration curve
Every time you ride with power, you produce a best effort for every duration: your best 1 minute, 5 minutes, 20 minutes and so on. Plot those bests and you get a power-duration curve. It slopes down, because you can hold less power the longer the effort lasts.
The critical power model fits a line to that curve. Critical power (CP) is the power you could theoretically sustain without using up your limited reserve for hard efforts above it. Some physiologists consider CP the best marker of the maximal metabolic steady state (Jones et al., 2019). CP and FTP aren’t identical, but in trained cyclists they were strongly correlated (r = 0.969) and close on average (Karsten et al., 2021).
Can everyday rides replace a test?
Researchers have tested this directly. One study compared lab-measured CP with CP built from the best 3-, 7- and 12-minute powers in riders’ routine training and racing. The field estimate had a standard error of 5.2% and high reliability between repeated trials (intraclass correlation 0.99) (Karsten et al., 2015). The authors concluded that field protocols produce valid and reliable CP values.
A study of 27 professional cyclists added an important nuance. During the competitive part of the season, CP and best 5- and 20-minute powers from training and racing data matched results from formal timed trials. Earlier in the season, they didn’t. The authors suggested specific tests may still be needed when only training data are available (Pallares et al., 2022).
The limits of testless FTP
That nuance is the whole challenge. A formal test is an all-out effort by design. Your rides usually aren’t.
- Outdoor bests often aren’t maximal. A 20-minute climb you rode at a comfortable pace looks like a “best 20 minutes” in the data, but it doesn’t show what you could do flat out.
- Missing data isn’t lost fitness. If you haven’t ridden hard in a few weeks, your recent bests will drop. That doesn’t mean your FTP did.
- Short efforts can mislead. In the professional cyclist study, best 1-minute power from field data didn’t match formal tests even late in the season (Pallares et al., 2022). Longer, sustained efforts tell you more about threshold.
So a good testless system needs rules: what counts as evidence, how big a change it can make at once, and when it should lower FTP versus simply waiting for better data.
How WattAscent’s Adaptive FTP works
Other apps estimate FTP without a test too. TrainerRoad’s AI FTP Detection, for example, tracks FTP without an all-out test. Where WattAscent differs is that we publish the rules, so you always know why your FTP changed.
WattAscent also counts more of your training. Any activity recorded with a heart rate monitor, in any sport, adds to your training load. For activities without power, it uses a heart-rate-based training load (Banister’s TRIMP), calibrated to your own power data so a hard run and a hard ride are measured on the same scale. That keeps your fitness, fatigue and plan accurate when part of your week happens off the bike.
Starting point
When you set up WattAscent, you choose one of three options:
- I know my FTP. Enter it. If you’ve connected Strava and saved an FTP there, it’s filled in for you.
- Estimate it from Strava. WattAscent looks at your best efforts with power from the last 60 days. It combines a critical-power fit with 95% of your best 20 minutes, takes the simple average, and never sets FTP below your best 60-minute power. It needs at least one effort of 12 minutes or longer.
- I don’t know it. WattAscent doesn’t guess. You do a Ramp Test before any other workout or plan.
The two-week FTP check
Every two weeks, WattAscent reviews your FTP using:
- your best efforts over the past six weeks, from WattAscent rides and tests and your connected Strava activities, and
- whether you’ve been completing hard indoor workouts.
Two weeks is long enough to collect several hard sessions as evidence, and short enough that your targets don’t fall far behind your fitness. You don’t have to schedule anything: the check runs in the background while you follow your plan.
The rules for raising FTP
When the evidence shows you’ve gotten stronger, FTP goes up, but by no more than 6% per check. The cap keeps one great day, or a data glitch, from setting targets you can’t hold.
The rules for lowering FTP
Lowering FTP takes stronger evidence: two failed workouts or more than 14 days off. That’s deliberate, because outdoor bests often aren’t all-out. A few weeks of easy riding shouldn’t drag your targets down when your fitness hasn’t changed.
After more than 14 days off, WattAscent also eases your plan by one intensity step while you get back into it. For more on how fitness fades, read How Fast Do You Lose Cycling Fitness?.
When you still want a test
You can test any time. WattAscent includes a Ramp Test (75% of your best minute), a 20-minute test (95%), an 8-minute test (90%) and a Durability test. Tests are useful when you’re starting out, coming back after a long break, or simply want a clean benchmark. If you have a heart condition or other health concern, check with your doctor before any all-out effort.
Making testless FTP work for you
- Include some hard, sustained efforts. Threshold intervals and long climbs ridden hard give the FTP check real evidence to work with.
- Connect Strava. Your outdoor rides and other activities count, so the check sees your whole training picture.
- Finish your workouts honestly. Completing, or failing, hard indoor sessions is part of the evidence.
- Trust the trend, not one ride. A single bad day won’t lower your FTP, and a single great day can’t raise it more than 6%.
To understand how FTP is defined and tested in the first place, start with What Is FTP?. Then see How to Increase Your FTP for the training that moves it.
Train with an FTP that keeps up with you
WattAscent’s Adaptive FTP keeps your targets current using the rides you’re already doing, with rules you can read. It’s part of AI-based training built on published sports-science research, for $99 a year with a 30-day money-back guarantee. Start training.
Frequently asked questions
Is FTP estimated from rides as accurate as a test?
It can be. Critical power built from routine training and racing data had a standard error of about 5% against lab values in one study (Karsten et al., 2015). Accuracy depends on your data including genuinely hard efforts, which is why WattAscent uses rules about what counts as evidence.
Why won’t WattAscent lower my FTP after a few easy weeks?
Because easy weeks don’t show your maximum. Outdoor bests often aren’t all-out, so WattAscent only lowers FTP with clear evidence of lost fitness: two failed workouts or more than 14 days off.
How much can my FTP go up at once?
No more than 6% per two-week check. If you’ve improved more than that, FTP will keep rising over the following checks as the evidence holds up.
Do I ever need to do an FTP test?
Only if you don’t know your FTP when you start, in which case the Ramp Test comes first. After that, tests are optional.
Does TrainerRoad also estimate FTP without testing?
Yes. TrainerRoad’s AI FTP Detection tracks FTP without an all-out test. For a side-by-side look at the two apps, read WattAscent vs TrainerRoad.
References
- Inglis, E. C., Iannetta, D., Passfield, L., & Murias, J. M. (2020). Maximal Lactate Steady State Versus the 20-Minute Functional Threshold Power Test in Well-Trained Individuals: “Watts” the Big Deal? International Journal of Sports Physiology and Performance, 15(4), 541–547. link
- Jones, A. M., Burnley, M., Black, M. I., Poole, D. C., & Vanhatalo, A. (2019). The maximal metabolic steady state: redefining the “gold standard”. Physiological Reports, 7(10), e14098. link
- Karsten, B., Petrigna, L., Klose, A., Bianco, A., Townsend, N., & Triska, C. (2021). Relationship Between the Critical Power Test and a 20-min Functional Threshold Power Test in Cycling. Frontiers in Physiology, 11. link
- Karsten, B., Jobson, S. A., Hopker, J., Stevens, L., & Beedie, C. (2015). Validity and reliability of critical power field testing. European Journal of Applied Physiology, 115(1), 197–204. link
- Pallares, J. G., Hernández-Belmonte, A., Valenzuela, P. L., Muriel, X., Mateo-March, M., Barranco-Gil, D., & Lucia, A. (2022). Field-Derived Maximal Power Output in Cycling: An Accurate Indicator of Maximal Performance Capacity? International Journal of Sports Physiology and Performance. link