Power Test: Failed

Having received a power meter and a copy of Training and Racing with a Power Meter it seemed like time to try and work out my Functional Threshold Power.

Obviously this isn’t the kind of test which usually has a pass/fail outcome; I failed in that I did not complete the test with a set of results which allows an FTP number to be calculated.

I made several errors:

  • I wasn’t feeling great, physically; I probably should have waited for another day.
  • It was less than two hours after breakfast; I probably should have waited a bit longer.
  • I didn’t warm up properly. At the end of my warmup my heart rate was only around 120 bpm when it should have been more like 145.
  • I started the sustained effort blocks at (it turns out) too high an effort (320 W) for me to sustain.

Since I am no good at pacing my efforts by feel I am going to adopt a different strategy when I re-run this test. I will take a guess at what my sustainable power levels are, and try to hold that number on the power meter readout. If I can do it too easily then the guess needs to be revised upwards and the test re-attempted. If I can’t complete the interval then the guess needs to be revised downwards and the test re-attempted. If the guess is close (but under) I can get a sensible result by speeding up in the final minute or two.

There are several ways I could formulate my initial guess. If I want to be a Cat 4 racer I should have an FTP/mass of around 3.29 W/kg which given I weigh 75.5 kg requires an FTP of 248 W. I don’t like this method as I (currently) have no basis to believe I an compete as a Cat 4 racer.

Instead I am going to presume that the power numbers from my warmup/recovery/cooldown sections are in the lowest “Active Recovery” power zone. This zone is all power outputs under 55 % of FTP. If I divide the upper decile power output from these sections (141 W) by 0.55 I get an FTP estimate of 256 W. I will be pleased if this is an underestimate. Since the FTP estimation method can be completed reasonably accurately with an initial underestimate (you can speed up at the end of a run) but can’t be completed with an initial overestimate (not completing the run invalidates the result) I am going to revise this estimate down to 240 W and go from there.

I am doing all of this on the turbo trainer: I don’t use the roads for training at or near peak performance because I feel that my capacity to observe and react to traffic are thereby diminished beyond the point of reasonable safety.

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