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How to Test with the 20-Minute & 8-Minute FTP Tests

With the Ramp Test as our recommended assessment, we still offer two alternative options to test FTP: The 20-Minute and 8-Minute FTP Tests.

How to Test

During the test intervals, totally ignore the graph's recommendations.

Whether you're above, below, or exactly in line with the graph makes no difference. It's important that these assessment efforts are not restricted or guided in any way. We're simply trying to get a reasonably close estimate of your Functional Threshold Power, something we can't do if your smart trainer is limiting your power.

FTP (Functional Threshold Power) is automatically calculated upon completion of any of our test workouts.

20-Min VS. 8-Min Test

If you do decide to use one of these alternative tests, whether you use our 20-minute Maximal Lactate Steady State (MLSS) interval or a set of 8-minute Power at VO2max (pVO2max) efforts, it's best to choose a format that you will stick with and one that fairly represents your fitness at the time.

Each test has its own pros & cons.  We'll elaborate on each of them briefly below in order to help you choose a format that best suits you, both in terms of your current capabilities & capacity for suffering.

20-Minute Test

The 20-Minute Test is an ideal format to break into shorter, more manageable segments. By breaking the 20-minute effort into four 5-minute segments, riders can subtly tweak their effort every so often based on longer periods of muscular feedback, i.e. a rider can slightly reduce their pace every 5 minutes based on perceived exertion or how their body feels.

The 20-minute test is a relatively long testing effort and pacing can sometimes be an issue for less experienced riders.  Because of this, the 20-Minute Test is usually more ideal for seasoned riders who have a good sense of how to pace well.

Additionally, many riders play it safe during the longer formats and end up finishing with too much gas left in the tank. Evidence of this is illustrated via a 2 or 3-minute surge in power at the end of an effort that would ideally be evenly-paced over the entire 20 minutes.

As a result, their FTP and relative power levels are likely to be underestimated a bit (or a lot) rendering all subsequent FTP-based workouts less productive than they would be otherwise.

TrainerRoad calculates your FTP from the 20-Minute Test by multiplying your average power for the test interval by .95. In other words, your FTP is 5% less than your average power of the test interval.

8-Minute Test

Our preferred format for less experienced riders is the 8-minute protocol comprised of two 8-minute efforts. 

The 8-Minute Test yields a greater amount of information by demonstrating power at VO2max via each 8-minute interval, sustainable power/FTP once the average power of the two 8-minute intervals is reduced by 10%, and you can even track improvements in your aerobic fitness when comparing the 2 efforts afterward, i.e. a substantial difference could indicate a limited ability to recover & insufficient aerobic capabilities.

TrainerRoad calculates your FTP from the 8-Minute Test by multiplying your average power of the two test intervals by .9. In other words, your FTP is 10% less than your average power of the two test intervals.

Erg Mode vs Slope/Resistance Mode

Building on the information found in our Erg Mode Explained article, these FTP test alternatives, when completed on a smart trainer, have to be done in the appropriate mode: Slope or Resistance mode (depending on your particular trainer).

Fortunately, TrainerRoad switches modes for you when you assess your FTP via our 20-Minute Test or our 8-Minute Test.

Why Erg Mode is Bad for the 8- and 20-Minute FTP Tests

If a smart trainer is left in Erg mode during the testing portion(s) of a 20- and 8-Minute test, the workout will lock you in at your current fitness level instead of allowing you to pace the duration of the test interval at your own power target.

To avoid this, the assessment needs to take place in Slope/Resistance mode in order to allow a rider to work at his/her own pace rather than having the trainer determine a pace based on the input FTP.

TrainerRoad automatically switches you to Slope/Resistance mode during your test interval(s).

If you wish to use a higher or lower Slope/Resistance setting, you're free to adjust it yourself and it makes no difference if you use different Slope/Resistance settings from interval to interval or test to test. The last setting you used will be applied the next time you enter Slope/Resistance mode.

By switching to Slope/Resistance mode, you're allowed to go hard without being forced to maintain the calculated Target Power that would be forced on your legs in Erg mode. You can pace according to your current capabilities such that you ride as strongly as possible for the assessment interval(s).


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