Your Most Important Number: How to Find Your Running Functional Threshold Power (rFTPw)

This story adapted from the upcoming book RUN WITH POWER by Jim Vance.

If you are now using a power meter for running, like the new Stryd or RPM2, you likely are wondering how you can utilize the tool to maximize the benefit of the technology in your training and racing. Power meters for running are a very new technology, and there is still a lot to learn ahead. However, to begin using it effectively to learn about your training and training response, you should begin as you would if you were using a cycling power meter.

First, simply train normally and observe the data as you train. Watch and see how the numbers fluctuate or correlate with different intensities, different inclines or declines, and more. Don’t try to control your training based on the power numbers now, as you don’t have a baseline for what they truly mean yet. At first, collect the data from your normal training and see how the numbers are trending.

When you feel you are ready, you can then test for your running functional threshold power, which I abbreviate rFTPw.

If you’re a triathlete who uses power on the bike, this number will not likely be the same as on the bike for you. In fact, your running FTP is likely to be larger than your cycling FTP. You may already use threshold pace in TrainingPeaks, or what I call rFTPa. I use these terms so not to confuse them with cycling, and especially not to confuse both pace and power when comparing or discussing FTP.

The Running Functional Threshold Power (rFTPw) Test

There are a number of ways you can estimate your rFTPw, but I will share one of the field tests you can do. One of the power meter companies, Stryd, came up with a test that I like, but which I have modified slightly. This test is much easier than an all-out 1 hour effort, or even 20-30 min effort. It simply is a 3 min all-out effort, and a 9 min all-out effort, separated by 30 mins. This test should be performed outside, on a flat surface, not on a treadmill.

Here’s the protocol:

  • Warm up for 15 minutes, preparing for a hard effort.
  • Run a 3-minute interval at maximal effort.
  • Recover for 30 minutes with a 5-minute walk, 10-minute easy jog, 5-minute walk, 5-minute easy jog, and 5-minute walk.
  • Run a 9-minute interval at maximal effort.
  • Cool down 10-15 minutes with easy running.

After you have complete this test, take the average power for the 3 mins and the 9 mins, and average the two values. For example, if you did 350 watts for the 3 mins, and 300 watts for the 9 mins, you would get a 325 watt average of the two.

After this, take 90% of that averaged value. This number is your estimated rFTPw and it should be within +/-3% of your actual value if your interval pacing was good.

For information on how to correctly set your rFTPw into TrainingPeaks, see my post on the TrainingPeaks blog here. The post there is basically the same as this one, but includes the information specific to using rFTPw with TrainingPeaks. If you have set your cycling power zones on TrainingPeaks, you will probably want to set your running power zones using the rFTPw you’ve just found.

Don’t do it.

The TrainingPeaks zones, while excellent for cycling, do not (yet) apply with run power meters. Trust me, I have researched it, and I will be coming out with my running power zones in another post soon, that work effectively for you.

In the meantime, just gather some baseline data by running with your running power meter. If you use TrainingPeaks, simply observe how your VI, IF and TSS values calculate based on easy efforts, hard efforts and everything in between.

We’ll get to Running Power Zones soon.


Run with Power by Jim VanceRUN WITH POWER is the groundbreaking guide you need to tap the true potential of your running power meter like SHFTStryd, or RPM2. From 5K to ultramarathon, a power meter can make you faster—but only if you know how to use it. Just viewing your numbers is not enough; you can only become a faster, stronger, more efficient runner when you know what your key numbers mean for your workouts, races, and your season-long training. In Run with Power, TrainingBible coach Jim Vance offers the comprehensive guide you need to find the speed you want.

Run with Power is available now from your local bookstore, tri or running shop, and from these online retailers:
Coach Jim Vance
Limited offers: Get Run with Power FREE with purchase of a SHFT, RPM2, or Stryd power meter while supplies last.

Also available wherever books are sold:
Barnes & Noble
local bookstores

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