What is FTP and Why is it Important?

By Colin Levitch

If you’re new to the of world power training and training apps there’s a whole host of new terms, figures and abbreviations you’re soon to become well acquainted with. One, in particular, you’re going to be seeing a lot of is Functional Threshold Power or FTP, as it forms the basis for almost every app and workout. But what is it and why is it so important?

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What is FTP?

Your FTP or Functional Threshold Power is commonly defined as the maximum amount of power, measured in watts that you can sustain for an hour.

Training apps like Kinetic Fit, TrainerRoad and Zwift use your FTP to calibrate workout intensity and measure fitness progression, and it is the most accessible gauge of fitness. For example, a tempo workout will prescribe intervals at around 75-percent of your FTP, and VO2 Max workouts will have efforts at around 120-percent of your FTP.

Before FTP, Lactate Threshold (LT) was the gold standard of fitness and fatigue, however, it was inaccessible to many as it requires a lab setting, which involved taking blood lactate measurements at set intervals while ramping up the intensity on a trainer. In their book, Training and Racing with a Power Meter, Hunter Allen and Dr. Andrew Coggan defined FTP as a more practical alternative to LT as they are functionally very similar when it comes to training, and can be determined at home using your trainer.

It’s important to note that FTP is a moving target, as your bike fitness gets better, the number will go up and it serves as a pretty good marker of how your training is coming along. However, FTP only measures sustained aerobic ability and doesn't take into account neuromuscular, max aerobic power and anaerobic capacity abilities  — what your body is capable of above FTP. Everybody’s body reacts differently above threshold, and that’s why some people are better at sprinting, climbing or time trialing than others.

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How do you figure out your FTP

With FTP being the max watts you can hold for an hour, to figure it out you should go out for a 1-hour slugfest, right? Not quite, there is a better way!

FTP tests are usually based around a 20-min steady state, max effort interval. Most training apps including Kinetic Fit offer an FTP test to guide you through the process and do the math for you. Learn more here.

But, if you want to do it yourself, get set up on your trainer and spin for 10 to 15-minutes to warm your legs up and mentally prepare yourself for what's to come. The first part of the test is two five-minute full-gas efforts with a 10-minute rest between them. This is to clear some of your anaerobic capacity before the long effort, making the power you can sustain over the 20-minutes a more accurate representation of your FTP.

After another 10-minute rest begin the 20-minute interval, the goal is to maintain as high a power as possible for the entire effort. Make sure you don’t go out too hard, it’s much better to start out a bit easier and take stock every five-minutes, changing your effort accordingly.

Once you’re done, use a program like Garmin Connect, Strava, TraningPeaks or Golden Cheetah to find your average power over the 20-min effort (not Normalized Power), subtract five-percent and voila, you’ve got an estimate of your current FTP. For the best results make sure you hit the lap button on your head unit or watch as you start the long interval.

I got my FTP, now what?

Now that you know your FTP, you can use that number to track your progress, and better calibrate your training zones. As you continue to train, your fitness will go up and so will your FTP. The test should be repeated roughly once every six-weeks to keep an accurate number.

With your FTP you can quantify those power numbers that light up on your head unit, and apply them to your riding and racing. When your buddies attack at the bottom of a climb, you know how hard you can go without blowing up before the top or if you go off the front at your local crit; now you can measure your effort and determine whether you can hold that pace and stay away, or whether you’re going to burn all your matches and get spat out the back when the bunch does catch you.