A 20 Minute Power-Based Field Test

Originally published at: https://fascatcoaching.com/tips/a-20-minute-power-based-field-test/

by Frank Overton, January 2015

One key question we ask ourselves as coaches at FasCat, is if the athlete is responding to the training we have prescribed. Aka, are they getting faster? Our favorite “experiment” to answer this question is a good old fashioned 20 minute power based field test, which is free and can be conducted anywhere and anytime appropriate.

Reality Cycling

In a former life and career, I conducted hundreds of experiments in a medical and biotechnology as a research scientist in laboratories designed to answer specific questions about the research projects I was working on. Spinal cord research, cancer, and novel cancer cures to name a few. At FasCat, we still perform “experiments” designed to evaluate our athletes’ current physiology as it relates to their cycling performance. Still to this day the most practical, most relevant test of all is a 20 minute power based field test. With the exception of a full gas 40k time trial.

In the past we have conducted MLSS tests in an exercise physiology lab, but the reality is that cyclists need to test two to three times per year which is cost prohibitive for many athletes. Plus indoor power tends to be slightly less that outdoor power. A properly conducted field test cuts to the core of cycling performance and gives a great physiological assessment of the athlete (1), making it an indispensable tool for our coaches or the self coached athlete.

How Do I Conduct a Field Test?

In essence, a 20 minute power based field test is riding as fast as hard as you can for exactly 20 minutes. Just like a 20 minute time trial. Record your average power output and use that number as a benchmark and to determine your wattage based zones*. When available we’ll recommend a steady grade hill free of stop signs, descents and any section of road that requires the athlete to stop pedalling. Ideally a 2-3% steady grade hill like this Strava segment. Steeper climbs tend to bog athletes’ cadence down which skews the test results. Conversely, some athletes make greater power uphill than they can on the flats. Whichever you choose, it is absolutely imperative that you ensure your test is repeatable, accurate and reliable.


Here’s how: For the road cyclist and mountain biker an all out effort similar to your time trial pace of 20 minutes elicits a physiological response that has been found to be “the single greatest determinant of cycling performance in mass start cycling events” (1). We have experimented with 60 minute Field Tests and honestly not that many athletes can sustain that sort of mental effort for the full 60 minutes. If they can its a mental match we don’t want to burn. On the other hand if we know the athlete can do a 60 minute field test once a year, it is the coaches discretion to prescribe one. It is especially beneficial to compare 60 minute field test data to ~ 60 minute 40k time trial data.

When choosing the roads for your field test let the terrain you have available dictate the specifics of your test (working within the 20 min range). After all, going for it from the bottom of a climb all the way to the top is more stimulating than working off your stopwatch. It may even be specific to your target event(s). For instance, a climber targeting a race with a decisive climb will want to specifically perform their test on a climb similar to the one found in the race. Heck, if you live nearby the race course, test on the race course! Conversely you may not even see a climb longer than one or two minutes where you live. That’s cool; then find a stretch of road to measure how far you can ride in 20 minutes. If this is the case, pay special attention to the wind and humidity which will affect your aerodynamics and thus time. As long as you come back to the very same piece of road and start from the very same spot, under the same test conditions, your test will be repeatable.

*We take the average 20 minute power and subtract 5 – 10% to arrive at an athlete’s 60 minute “Functional Threshold Power” or FTP. As a generally rule of thumb we use 5% for slow twitch aerobic athletes and 10% for athletes that have a well developed anaerobic system. We’ll subtract 7.5% if we don’t know about the athlete’s anaerobic capacity.

Field Test: 20 minuter


Whatever you have nearby, find a stretch of road free of stops signs, intersections and corners — anything that would slow you down. In essence: go as hard as you can! Don’t hold back one bit, go for it! Now here’s the catch: remember everything about this test and duplicate it for your next test.

Items to keep the same (& ensure repeatability) include:
  • Your powermeter! Calibrated of course. Different powermeters unfortunately produce different results
  • Your bike: weight (including water bottles), body position, tires, tire pressure.
  • Your kit: jersey, shorts, helmet – – essentially you want to have the same aerodynamic characteristics from test to test.
  • Wind and weather conditions: test on a windless day under the same humidity – air density affects aerodynamics too!
  • Temperature: avoid testing between extreme temperature differences.
  • Come into the test rested, properly fueled, well hydrated with tons of motivation (you gotta go full gas!)
  • Perform the exact same warm up before each field test.
  • In a nutshell keep everything the same except for your fitness.

Being able to compare tests and controlling for all other variables except your physiology or fitness allows you and your coach to interpret the efficacy of your training. These details may seem picky but are necessary to draw accurate comparisons.

Your results:

Test at the beginning of your training and then again after 8-12 weeks to measure your improvement. If your power goes up, guess what? Your training is working, keep going. If your power goes down or stays the same, guess what? Your training is not working and you need to change what you are doing. Its as simple as that.

All of our Six Week $49 Training Plans culminate with a field test so you can measure how much faster you’ve become!

Field Test Workout

Test not once, but twice, or more

If you have a new powermeter or are beginning a training program, perform a “baseline” field test for two reasons:

• To determine your wattage based training zones
• To establish a benchmark to measure future improvement

For a good test ‘performance’, approach the day with a minimum of 24 hours rest and go absolutely as hard as you can during the test. If you don’t, the results will be inconclusive. Record the average power and continue with your next training cycle. Come back to the very same field test in 6-8 weeks under the same rested conditions and go for it again. By comparing the two average power outputs, you will be able to draw useful conclusions about your training. i.e. is it working? Test periodically throughout the year (we recommend no more than 3 times*) and carefully record your results in your training log. This will paint a big picture that is extremely useful when plotting out your next move and planning your next winning season.

Regular testing is THE BEST way to track performance and we do not recommend using mean maximal, mFTP or power profile charts that cull non “as hard as you can go” power outputs. By performing 20 minute tests, you’ll also be able to compare this data with race data. For example, time trials where you went as hard as you could for 20 minutes or breakaways and long climbs.


• Go as hard as you can for the full 20 minutes
• Upload your data and analyze the average power output
• Make sure the test is 100% repeatable to eliminate all variables except your average power output improvement
• For indoor 20 minutes tests, see our indoor cycling 20 minute tip

Finally, testing yourself is a great start, but remember the ultimate measure of performance is performance itself. So get out there in a race, go hard, and duke it out! For further reading, please read the “Determining Threshold Power” training tip on VeloNews.


E.F. Coyle, A.R. Coggan, M.K. Hopper and T.J. Walters, “Determinants of endurance in well-trained cyclists.” J Appl. Physiol 64:2622-2630, 1988

Copyright 2017 , FasCat Coaching

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Frank is the founder, owner and CEO of FasCat Coaching in Boulder, CO. He is a full time professional USA cycling certified Elite level coach, former category 1 road racer; semi-pro mountain biker and nowadays a ‘master’ category cyclocross racer. Frank & FasCat prescribes field tests all over North America and Europe and locally chooses Lefthand Canyon in Boulder, CO for FasCat Athletes to test up. To talk with a FasCat Coach about the same testing described above, please call 720.406.7444 or fill out a New Athlete Questionnaire to set up a Coaching Consultation. Additionally all of FasCat’s training plans have field tests prescribed for optimal performance.

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I have a couple of questions. My first field test for my current training episode was done with the Coggan method. I have my 2nd one due this Wed. I was planning on doing the 20 minuter per Fascat (rather than Coggan method and wondered if that mattered). My other question is, since I’m training by Heart Zones, what Field Test result would indicate I am getting stronger? I wondered whether my avg HR would be lower because I’m in better shape, rather than higher, but thought I’d ask. In the last 2 weeks, I have posted personal record times up 2 local climbs! Thanks.

Hiya @markmueller - thanks for your question, to what Coggan method are you referring too ? He and I are in agreement with everything.

in this podcast if you go back an listen again I touch on this - you measure how much further you travel in the 20 minutes. 100 feet or 1,000 meters - that’s how you’ll measure your improvement.

HR won’t be lower - “it never gets any easier you just go faster” to quote Greg Lemond.

PR’s on Strava are a good indication too!

Sorry, my bad, I did the CTS–carmichael training–field test based on Coggan field test. CTS is two 8 min. intervals. Wondered whether to do that again or just do Fascat 20?

You always want to #FtFP . There’s a 20 min test for a reason.

An 8 minute test is garbage and Coggan would never associate with that.

To add - 8 minutes is too short of an effort to elicit a threshold response.


Sorry, I do have another question: the triple bypass has now postponed to 9/26/20 and I’m in to week 21 of about 33 total (resistance and sweet spot)–what would be a good plan in terms of staying in shape/prepping for it until that time? I believe there’s 19 weeks until 9/26.

Keep following your plan until the end and then get into our triple by pass plan for the six weeks prior to the triple bypass:

If there’s a gap work on your climbing with our climbing intervals plan:

:ok_hand: Thanks appreciate the advice.

Just listened to the May 8th, 2020 podcast on the 20 min power test. Maybe my theory is off here but I have experimented with the 1 min ramp, MAP, 10 min steps, and 20 min power and have come to the conclusion that I actually like the MAP (30w every 3 mins). The reason being is that I have noticed that zones outside FTP seem to vary in which a straight 20 min power does not capture. Like after tons of base training I can ride closer to a FTP that has not changed that much (validated with lactate testing where my 2 mmol output increased by 30w while my ftp only went up a few watts) and it is a little less taxing. Other than that, it takes out the pacing issue and whether you are 90%-97% of your 20 min power out of the equation. You need to perform it on a trainer which may make it more consistent. It helps to know your lactate values to guide your zone setting but you can still witness the change in HR vs power and different levels without it (3 mins is a good amount of time to stabilize). I have found my lactate is very related to my HR and does not change (ie ~143 bpm is always 2 mmol) so in other words, if you do it once or twice, then you will have a good idea of your lactate levels based off your HR at any time.
Lastly, using this protocol, I found my 20min is 91% of my MAP.
Does this seem logical with this background info to opt for MAP tests over 20 min field tests?

One of the biggest points I tried to make in the podcast was simplicity and creating the ability to monitor FTP throughout the season by:

20 minutes as hard as you can in the aforementioned field test
20 minutes as hard as you can in a group ride
20 minutes as hard as you can during interval training
20 minutes as hard as you can going for a strava segment
20 minutes as hard as you can in a RACE

That’s 5 apples-apples data points from March - September (for example) that make a nice data set. Can your MAP test do that?

I see your point. I guess the problem I have is I rarely, if ever, hit those levels in races (last break I made, I was still under ftp by a good 70w over an hour) or group rides, especially these days when there are no group rides or races, for intervals I FtFP so usually don’t go over the prescribed intensity so am pretty much forced to test if I want to see where I am at. Maybe strava but I don’t bother trying there as everyone on the leaderboard around here is like a 6+w/kg rider.

There is something to be said about the repeatability and control from a GXT test but I have found over the years athletes dig the deepest when it matters - usually when there’s a number on their back, i.e. in a competitive situation.

By setting yourself up to have your test data match your real world power data you’ll form a much better data set year to year, historically.


Hi Fascats,

I have a question regarding an upcoming field test. I’ve only ever done ramp tests and I’m afraid to overdo the pacing on a 20min effort. From experience, such tests also tend to overestimate my FTP. I’ve done done a 20 field test outside last summer for the sake of FTfPing, but without any power data on my bike, it’s hard to tell how it went pacing-wise.

In the week leading to the field test, there’s a 2x10 sweet spot workout. Should/can I go ahead and perform the 2x10 intervals full gaz in preparation for the test the week after?

A field test in its essence it simply you going as hard as you can for 20 minutes straight. If you do just that, you’ll ‘do it correctly’

Focus on that and as you do more and more field tests and have previous data and a sense of what you can do for twenty minutes, you’ll get a feel for what’s possible and be more informed.

Don’t limit yourself - see what you can do from a max effort for 20 straight minutes. Hindsight will be 20/20 but that’s the knowledge you’ll bring to the next time you test.

If I could give you more accurate information I would but it is simply a case of don’t know till you try.

Have the Eye of the Tiger and Cry in the DoJo to Laugh on the Battlefield!

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Back in August my ftp was 237.
I then joined Fascat bought ss4 and later winter plan + Weight Loss Plan.
Yesterday my dreams came true.
Hit 301 ftp on my Field Test
@Allie @Jake


Yeah baby!!! Great work!!!


Congrats @efty19 ! Welcome to the 300 watt club :muscle:

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Just wondering is it time for another test? My last one was 2nd Feb and next one is scheduled for 12th June as per ss4. I feel stronger but maybe I’m fooling myself? @Allie

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That is ~3 months between field tests which is just about right.
The good news is that until then you do not have to do another test to see if your power has increased if you have some good group ride/race data that you can analyze :wink:


The Lefthand Canyon route referenced in your article can be found on Rouvy & includes video of the route. I’ve ridden the route in VR & plan to test on it in a few weeks.