How to measure your FTP without (too) much effort
You train at home and the app you use requires you to enter your FTP. The problem is that the methods usually suggested for doing this are imperfect and tedious. So here's how to find the right number without killing yourself in the process.
Several commercial applications offer us the possibility of developing and executing interval training sessions (ITS) suited to our fitness level (Zwift, TrainerRoad, PerfPRO Studio, Sufferfest, etc.). As with Vélo Cartel workouts, the sessions developed using these apps are personalized in that the intensity of the repetitions and active recovery periods is expressed as a relative value based on an objective measure of our aerobic fitness.
The problem is the difficulty of finding a reliable baseline measurement from which to calculate all the efforts that need to be made.
For most commercial applications, we recommend using the aerobic fitness index. This is known as Functional Threshold Power (FTP). The concept of FTP is poorly named and often misunderstood. Not to mention that measuring FTP requires a test so arduous (60 or 20 minutes of exhausting effort) that one is not tempted to do it regularly.
True FTP
FTP is supposed to be the pedaling power at which blood lactate concentration reaches a stable plateau. Some people argue or believe that it is a "threshold" intensity that can be maintained practically indefinitely. This is a far-fetched idea, as there is no intensity that can be maintained indefinitely.
Measuring true FTP requires a series of efforts at increasingly higher intensities and blood sampling. The goal is to find the highest stable concentration of lactate in the blood (known as MLSS, or maximal lactate steady state). This is therefore rarely done outside of research protocols. Or perhaps by professionals for whom undergoing such torture is part of their job.
Simplified FTP
Generally, commercial PTE applications present FTP as the highest power that could be maintained on average during a maximum test (leading to exhaustion) of 60 minutes. Since such a long test is quite challenging, a 20-minute test is generally offered, and then 5% is subtracted from the result to estimate the power that could be maintained for 60 minutes. This power is equated to FTP. Example: if you maintain 300 watts for 20 minutes, it is assumed that your FTP is 285 watts (95% of 300).
However, to obtain a more reliable figure, each individual's endurance index must be taken into account. This could cause the calculation to vary significantly. For example, a low index would result in an FTP of 85% of the 20-minute test result, a medium index would result in 90%, and a good index would result in 95%.
Other option
Fortunately, there is a more user-friendly and appropriate option. Instead of imposing a 60- or 20-minute test on yourself, simply take a test to assess your maximum aerobic power (MAP).
Protocol
This assessment test is progressive, in 1-minute increments, and maximal. Ideally, use a training base such as the Saris H3, in ERG mode, i.e., with the power imposed. This will ensure that you maintain the correct power throughout each completed minute. Also: keep the same cadence throughout (to within about 5 RPM) and remain in a seated position.
After a standard warm-up, start the test at a low intensity: 10 or 20 watts more than your average warm-up intensity. Increase the intensity by 10 watts every minute until you can no longer pedal at the required power. The power of the last completed step is your MAP.
To estimate your FTP, subtract 15% from your result, and use this estimate of your FTP to use the commercial application of your choice.
Being maximal, this test is demanding, but since the intensity is only high in the last two or three stages, it is a test that virtually all cyclists prefer to the continuous 20-minute test.
Especially since, to do a 20-minute test, you need to know yourself a little and have an idea of how much power you can maintain for that length of time. That's far from obvious if you've never done it before.
Going further
Furthermore, if you want to take the exercise a step further and refine your training afterwards, this very simple PAM test will be very useful for conducting a real 20-minute test to gauge your endurance level. (We also have an excellent protocol for this test, which avoids the most common mistakes made during this type of exercise.)
If you have long expeditions, gravel or mountain bike races covering several kilometers in mind that require you to develop your endurance, this test, even if done remotely under our supervision, can help you identify your strengths and weaknesses in this area. We can then offer you customized programs that you can download via your home training app or road computer (Garmin, Wahoo) to use outdoors.
For more details on this subject, please contact us!
Thanks to my friend Guy Thibault for helping me write this Vélo Cartel column. Guy has a PhD in exercise physiology and is the director of sports science at the Institut national du sport du Québec and an associate professor at the School of Kinesiology and Physical Activity Sciences at the University of Montreal. His website is nature-humaine.ca. Check out the 3-2-1 Go! app that we developed together: https://nature-humaine.ca/2017/11/3-2-1-go/
To learn more
Guy Thibault, Cardio Training. Endurance Sports and Performance, Vélo Québec Éditions, Géo Plein Air collection, 2009, 264 p.