Every FTP test protocol depends on the one thing that is really hard (and unpleasant) to do: truly go as hard as you can.
The new FTP Tracker in CoachCat solves that problem for you with your existing power data. Plus, our AI analysis also uses your heart rate and your Level (CoachCat's daily measure of how much you have been training) to increase the accuracy and degree of confidence we have in the result. No test is required to get your number, although hard efforts make your FTP determination more accurate.
Key Takeaways
- Every FTP test, and the critical power curve, needs a truly maximal effort, and most riders' files are nearly empty of them.
- CoachCat reads every effort against your heart rate, so hard but not maximal rides still help find your FTP.
- We use your Level (training load) to know whether your FTP has gone up or down from the amount of training you have been doing lately.
- Every number comes with a degree of confidence, and the Tracker tells you when one hard effort would raise it.
01 · The problem
The Problem: Going as Hard as You Can
An FTP test means going as hard as you possibly can, on purpose, and it hurts.
That is the first problem. The 20 minute test, the ramp test, the 8 minute test, the full hour: each one asks you to empty the tank. So you dread it. Your legs don't feel great, it's cold, it's windy, you hate going hard on the trainer, you will do it next week. Every excuse you have ever used to skip a race works just as well for a test.
Execution is the next hurdle. Start too hard and fade. Start too easy and leave watts on the table. Sleep badly the night before. Each one gives you a number that is wrong, and not a little wrong. Wrong enough to set every training zone you ride for the next eight weeks too low or too high.
A maximal effort is hard to produce on demand. That is the problem. It is why most athletes test rarely, test poorly, or skip testing altogether and ride on an FTP that is months out of date.
The critical power curve looks at every ride, not one test.
Instead of betting everything on one test on one day, the critical power curve plucks out your best power outputs at every duration, from 5 seconds to 60 minutes and beyond, from all of your rides, not a single day. It rests on sixty years of exercise physiology, from Monod and Scherrer's original work capacity model to today's power duration research1 to 7.
- No single effort carries the whole load. The curve smooths out the bad days.
- It finds the shape of what you can actually do.
Critical Power curves still need maximal efforts to be accurate.
Same problem, different costume. The curve is only as good as the data points that build it, and it cannot tell a hard effort from a maximal one on its own.
- The group sat up at 4 minutes. Your hardest 5 minute effort was a surge that ended early, so the curve sits below your real ability at 5 minutes.
- The climb topped out at 3:40. Your best 5 minute power is 3:40 of climbing plus 80 seconds of coasting, and the curve calls it your 5 minute best.
- No true 20 minutes since spring. The curve at 20 minutes describes the athlete you were in spring.
In the language of the science, the problem is an incomplete data set. The model needs maximal efforts at several durations to find the shape of the curve. A rider might have an honest 20 minute effort from a club time trial and no honest 5 minute effort in months, because nobody goes all out for 5 minutes by accident. Fit the curve to that and the short end is wrong, which pulls the long end out of shape too.
Even a perfect curve describes the days those efforts happened.
Fast in July, and three easy weeks since. The curve still says July. Or the reverse: you have been training more than ever, you are fitter than any effort in your file, and a power only curve has no way to know. Your FTP goes up with training and down without it. A curve built from past efforts cannot see either.
Two tools, one missing ingredient
Most riders' power files are full of hard efforts and nearly empty of truly maximal ones. So you end up with two tools that both depend on the one thing athletes reliably fail to provide, and neither one knows what day it is.
| Method | What it needs | What goes wrong | What it costs you |
|---|---|---|---|
| 20 minute test | One all out 20 minutes, then 95 percent | Paced wrong, or 4 percent too easy. The multiplier is wrong for diesels one way and punchy riders the other. | Eight weeks of zones set too low or too high |
| Ramp test | Ride to failure on a rising ladder | Rewards a big sprint, punishes a big engine | An FTP that does not match the hour |
| 8 minute test | Two maximal 8 minute efforts | Easy to leave something in the tank on the second one | Same as above, with more suffering |
| Full hour | One maximal 60 minutes | Almost nobody does one outside a race | Months between real numbers |
| Critical power curve | Maximal efforts at several durations, from any rides | Hard efforts and maximal efforts look the same to it, and most files are missing the short ones | A curve that describes the athlete you were, not the one you are |
Most riders' power files are full of hard efforts and nearly empty of truly maximal ones. The curve cannot tell the difference on its own. That is the whole problem in one sentence.Frank Overton FasCat founder, former Cat 1 racer, invented sweet spot training in 2005
02 · The solution
The Solution: We Analyze Your Data and Tell You Your FTP
CoachCat analyzes and learns the relationship between your power and your heart rate to help determine your FTP.
Heart rate is the honesty check. Across your whole history, CoachCat works out what a true maximal effort looks like at each duration. Efforts that qualify build your critical power curve. The rest are read for what they are.
- Say you rode 240 watts for an hour at 90 percent of your threshold heart rate. We know your FTP is greater than 240 watts.
- The curve is built on the efforts where you had nothing left, and the other efforts set a floor beneath it.
Wattage from your not as hard as you can go efforts fixes the incomplete data set. Hard efforts set your curve, and wattage from sub maximal heart rate data helps fill your curve. A 20 minute "as hard as you can go" effort helps to set the curve, as well as a 5 minute wattage effort at 90 percent. CoachCat uses heart rate data to understand how hard you were going and therefore what wattages to use in the model.
It learns your threshold heart rate from your own rides.
There is nothing to type in and nothing to get wrong. It just needs a few weeks of riding with a heart rate monitor strap. Threshold heart rate holds steady within a season even as your power changes, which makes it a stable reference against which every effort can be read.
If you rarely go hard, CoachCat has less to learn from, but your threshold shows itself in ordinary training too. A steady tempo or sweet spot ride at a known power and heart rate narrows where it sits. The more honest efforts in your file, the higher CoachCat's degree of confidence in the number, and the Tracker will tell you when one hard effort would raise it most.
FTP is the power your curve says you can hold for 60 minutes.
That is what FTP has always meant, the best you can do for an hour. CoachCat reads the curve with your heart rate and anchors it to your longest honest efforts, so the hour is what you can actually hold rather than a mathematical extrapolation from short efforts. No 20 minute multiplier that is wrong for diesels in one direction and punchy riders in the other.
What changes when heart rate joins the curve
A power only curve sees watts. With heart rate beside them, every effort gets read for what it was, and the curve is built only on the ones that count.
| The ride | A power only curve sees | With heart rate, CoachCat sees |
|---|---|---|
| A hard 20 minutes with heart rate at threshold | Your 20 minute best | A maximal effort. The watts are real and they build the curve. |
| An hour at 240 W, heart rate a little below threshold | Your 60 minute best, taken at face value | A sub maximal effort. Your FTP is above 240 W, and the curve is not dragged down to it. |
| A long sweet spot ride at a known heart rate | Nothing useful | A narrow range for where your threshold sits. Almost as much as a test. |
| Climbs separated by descents | A 20 minute best that includes coasting | An effort whose heart rate never settled near threshold. Discounted. |
| Power 50 percent higher at the same heart rate as last week | A breakthrough | A power meter fault. Set aside, with a note. |
Every number comes with a degree of confidence.
CoachCat does not just hand you a number. It tells you how much evidence sits behind it. A recent maximal effort with heart rate at threshold, best efforts spread across short and long durations, a strap worn on most rides, and a Level that has not moved far since those efforts were set: that is a high confidence number. Six months since your last hard effort, no strap, and a big change in training since: the number still stands, but CoachCat says so, and tells you what would raise its confidence. Usually that is one hard effort. Here is what that breakdown looks like for one rider.
- 1Your FTP SetYou set your FTP at 260W on October 27, 2026.32%
- 2Sustained 60 minute power 60 minYour best 60 minute effort of 234W sits on your power duration curve.24%
- 3Power duration fit Curve7 maximal efforts fit one consistent power duration curve.18%
- 4FTP history TrendNot enough accepted FTP values to show a trend yet.14%
- 5Durability Long ridesRides over two hours back the durability signal.12%
This is the same engine we used to analyze a full season of a WorldTour team's power data.
03 · Level
Level: Bringing the Number to Today
The curve knows July. Your Level knows today.
A critical power curve, even a perfect one, only describes your fitness on the days those efforts happened. Heart rate fixes which efforts count. It cannot tell you what has happened to you since.
Level is CoachCat's daily measure of your training load. It moves every day whether or not you test, so it is the one signal that knows what you have done since your last hard effort.
There is a clear relationship between your Level and your FTP.
The more you ride, the faster you get, up to a point13, 14. We have a training tip on it, and Exhibit 5 shows the shape of a season.
- Through a base phase your Level climbs and your FTP climbs with it. That is the sweet spot base doing its job.
- A recovery week dips your Level without costing you fitness, and CoachCat knows the difference.
- Once intervals start, your Level holds and your FTP keeps rising. That last stretch is why a new maximal effort always wins.
Your Level carries the number from your last hard effort to today.
Your FTP goes up with training and down without it. When the curve's data has aged, CoachCat compares your Level now with your Level when those best efforts were set.
- Level lower than when your best efforts were set: your number comes down to match. A 60 minute effort of 250 watts six months ago, at a Level 25 percent higher than today, still counts, but for what you can do today, not what you could do then.
- Level higher than when your best efforts were set: your number comes up. You have been training more than the data shows, and you are faster than your file says.
- How much, in either direction, comes from your own history of how your FTP has tracked your Level, not a generic formula.
CoachCat also notes when your last maximal effort was. If it has been more than about six weeks, your degree of confidence drops and the Tracker will tell you a hard effort would raise it. When that effort arrives it is the final word.
04 · How we do it
How We Do It
The analyses under the hood, in plain language. Then all four factors and the guardrails in one place.
1. Every duration counts, not just 20 minutes.
CoachCat looks at your best 1, 5, 12, 20, 30, 40 and 60 minute efforts, plus the whole power curve from 5 seconds to 3 hours.
- A hard climb on Saturday and a race on Sunday both feed the number. You do not have to schedule a test.
- A maximal hour is your FTP, full stop. A maximal 40 minutes is nearly as good.
2. Heart rate decides how much to trust each effort.
Every best effort in your file is read against the heart rate behind it.
- Heart rate at or near threshold: the effort was maximal. The watts are real and they build the curve.
- Heart rate well below threshold: the effort was sub maximal. It sets a floor, your FTP is at least that, and the curve is not bent down to meet it.
- Heart rate never settled, like a climb broken up by descents: the effort is discounted.
One rule holds throughout. Heart rate decides how much each effort counts, never more than the watts show. Your hardest real effort sets the ceiling on what the curve can say.
3. Heart rate catches a broken power meter.
Your watts at a given heartbeat are remarkably consistent, ride to ride. When a meter starts reading 50 percent higher at the same heart rate, that is a fault, not a breakthrough. Those rides are set aside and you will see a short note when it happens.
How the FTP Tracker works, on one page
Four factors, each with a job, and a set of guardrails that keep the number from moving for the wrong reasons.
| Factor | What CoachCat looks at | What it protects against |
|---|---|---|
| Every duration | Your best 1 to 60 minute efforts and the whole curve, from any ride | Betting everything on one test on one day |
| Heart rate | How maximal each best effort really was | Sub maximal efforts dragging the curve down, and an incomplete set of efforts bending it out of shape |
| Power at a given heart rate | Whether your watts per heartbeat match your history | A faulty power meter being read as a breakthrough |
| Level | Your training load now versus when your best efforts were set, and how your FTP has tracked your Level before (Chapter 3) | A number that describes July when it is October, in either direction |
The guardrails
- Your FTP moves on evidence: a new maximal effort, or a sustained change in your Level. Never on a hunch.
- A rest week or a taper is not a layoff. The number comes down only when your Level has fallen for long enough to mean lost fitness, and then it comes down the way fitness actually leaves the body: gradually, not in one cliff.
- Level moves the number by what that change in load has meant for you before, from your own history, so a big jump in training does not produce a big jump in FTP overnight. The Level section above has the whole story.
- A new maximal effort always wins. Whatever Level has projected, your next hard effort resets the number to what you actually did.
A true maximal effort still raises your degree of confidence, and the Tracker will tell you when one is overdue. The difference is that you no longer have to manufacture one on a Tuesday in order to know where you stand.Frank Overton FasCat founder, former Cat 1 racer, invented sweet spot training in 2005
Now go see your number
Keep riding. The Tracker is built from your data, so the more you ride, and the harder you go when the workout calls for it, the higher the degree of confidence behind your number.
Open the FTP Tracker, compare the FTP our analysis determined with the one set in your profile, and update it in one tap.
See my FTP Tracker →Sync your rides and CoachCat determines your FTP from the riding you have already done, sets your training zones, and gives you a benchmark to measure every improvement from here. No test required.
Start a free trial →05 · References
References
CoachCat uses a combination of scientific approaches: the critical power model, heart rate, training load, and the common FTP testing protocols. The critical power model dates to 1965, its use with everyday ride data has been validated in the field, and the gap between 95 percent of 20 minutes and a true hour has been measured three times over. The small orange numbers in the exhibits point here.
The critical power model
Where the curve comes from: the original work capacity model, the link to the anaerobic threshold, and the modern reviews that define critical power as the boundary between sustainable and unsustainable exercise.
- Monod H, Scherrer J. The work capacity of a synergic muscular group. Ergonomics. 1965;8(3):329-338. doi:10.1080/00140136508930810
- Moritani T, Nagata A, deVries HA, Muro M. Critical power as a measure of physical work capacity and anaerobic threshold. Ergonomics. 1981;24(5):339-350. doi:10.1080/00140138108924856
- Morton RH. The critical power and related whole-body bioenergetic models. European Journal of Applied Physiology. 2006;96(4):339-354. doi:10.1007/s00421-005-0088-2
- Jones AM, Vanhatalo A, Burnley M, Morton RH, Poole DC. Critical power: implications for determination of VO2max and exercise tolerance. Medicine & Science in Sports & Exercise. 2010;42(10):1876-1890. doi:10.1249/MSS.0b013e3181d9cf7f
- Poole DC, Burnley M, Vanhatalo A, Rossiter HB, Jones AM. Critical power: an important fatigue threshold in exercise physiology. Medicine & Science in Sports & Exercise. 2016;48(11):2320-2334. doi:10.1249/MSS.0000000000000939
Critical power from everyday rides
Evidence that a valid curve can be built from training and racing data rather than a laboratory, and the current consensus on power profiling in cycling.
- Karsten B, Jobson SA, Hopker J, Stevens L, Beedie C. Validity and reliability of critical power field testing. European Journal of Applied Physiology. 2015;115(1):197-204. doi:10.1007/s00421-014-3001-z
- Leo P, Spragg J, Podlogar T, Lawley JS, Mujika I. Power profiling and the power-duration relationship in cycling: a narrative review. European Journal of Applied Physiology. 2022;122(2):301-316. doi:10.1007/s00421-021-04833-y
Why 95 percent of 20 minutes is not the hour
Three studies that compared the 20 minute shortcut with a real 60 minute effort or with critical power. Each found small average differences and wide individual ones, which is Exhibit 2 in one sentence.
- Borszcz FK, Tramontin AF, Bossi AH, Carminatti LJ, Costa VP. Functional threshold power in cyclists: validity of the concept and physiological responses. International Journal of Sports Medicine. 2018;39(10):737-742. doi:10.1055/s-0044-101546
- Morgan PT, Black MI, Bailey SJ, Jones AM, Vanhatalo A. Road cycle TT performance: relationship to the power-duration model and association with FTP. Journal of Sports Sciences. 2019;37(8):902-910. doi:10.1080/02640414.2018.1535772
- MacInnis MJ, Thomas ACQ, Phillips SM. The reliability of 4-minute and 20-minute time trials and their relationships to functional threshold power in trained cyclists. International Journal of Sports Physiology and Performance. 2019;14(1):38-45. doi:10.1123/ijspp.2018-0100
Heart rate as the honesty check
Threshold heart rate holds steady within a season even as power rises, and power at a fixed submaximal heart rate predicts performance. Both are why a strap lets CoachCat read how hard an effort really was.
- Lucía A, Hoyos J, Pérez M, Chicharro JL. Heart rate and performance parameters in elite cyclists: a longitudinal study. Medicine & Science in Sports & Exercise. 2000;32(10):1777-1782. PubMed 11039652
- Lamberts RP, Swart J, Noakes TD, Lambert MI. A novel submaximal cycle test to monitor fatigue and predict cycling performance. British Journal of Sports Medicine. 2011;45(10):797-804. bjsm.bmj.com/content/45/10/797
Training load
The systems model of training that underlies Level and every fitness and fatigue tracker since, and a field study in road cyclists showing that training load tracks the changes in fitness and performance that follow. The relationship between Level and FTP is Exhibit 5, in Chapter 3.
- Banister EW, Calvert TW, Savage MV, Bach T. A systems model of training for athletic performance. Australian Journal of Sports Medicine. 1975;7(3):57-61.
- Sanders D, Abt G, Hesselink MKC, Myers T, Akubat I. Methods of monitoring training load and their relationships to changes in fitness and performance in competitive road cyclists. International Journal of Sports Physiology and Performance. 2017;12(5):668-675. doi:10.1123/ijspp.2016-0454
Keep reading
- The 20 minute field test: if you want to add a true maximal effort, here is how to do it right.
- FTP versus critical power: where the curve came from and what it adds.
- Training load and FTP: why your Level and your FTP move together.
