The purpose of an FTP test is to find you maximum sustainable power output. Within TrainerRoad, we do this through either the 8 Min Test or the 20 min test. In these tests, there are set testing intervals. and duringthese intervals you are expected to ride as hard as you possibly can for the entire interval. Your FTP will be calculated by multiplying a set factor by your average power for the interval. You can learn more about how your FTP is calculated in this article.
The most important advice for completing your FTP test is to IGNORE THE TARGET POWER during your test inteval.
Whether you're above, below or exactly in line with the graph makes no difference- you should be riding as hard as you physically can for the given interval. It's important that these assessment efforts are not restricted or guided in any way.
Check out the videos below to get an in depth look on how you should attack each test.
The 20-minute test is the preferred format for newer riders primarily because new riders simply don’t have an established feel for riding well above FTP — which is what’s necessary during the short, VO2max efforts necessary for the 8 Minute Test.
It’s also 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 downside is simply that it’s a relatively long effort and pacing is an issue for less experienced riders.
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.
Our preferred format for more experienced riders is the 8-minute protocol comprised of two 8-minute efforts. This format 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.
Past the initial assessment, riders can also observe changes in FTP, and arguably as important, compare power at peak aerobic uptake/VO2max from assessment to assessment, information that can be of particular value to competitive riders and exercise science geeks.
Testing on an ERG Trainer
Erg Mode vs Slope/Resistance Mode
Building on the information found in our Erg Mode Explained article, assessing FTP on a smart trainer has 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 either of our FTP Tests.
Why Erg Mode is Bad for Assessment
If a smart trainer is left in Erg mode, any test workouts won't assess FTP improvement because the workout will scale the assessment interval(s) to the FTP listed in your profile.
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.
In the case of a first-time assessment for a new TrainerRoad athlete, using Erg mode could be even more problematic since the default value for a new rider's FTP is 200. This standard value will likely be too high or too low unless your fitness happily coincides with the default 200 watts.
When you assess your sustainable power using one of our two test formats, TrainerRoad's workout player will automatically switch to Slope/Resistance mode just prior to each test interval.
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.
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).