Thursday, February 5, 2009
Functional Threshold Power - February
A little over a month ago I did a 12 mile time trial in order to measure my CP30 and estimate my functional threshold power. Today I went back for my 30 day checkup. Once again I returned to Fiesta Island for a 3 loop, 12 mile TT which usually takes me just a shade over 30 minutes to finish. If you'd like to see the power data for my test, I think you can view it online with this URL.
I began with a 15 minute warmup loop - which was enough to realize that this was going to be a windy day. It was 12 to 15mph wind, which means half the loop is a strong headwind, and half is a tailwind. It's nice that it evens out like that, but it means that its more difficult to do a steady effort. Luckily and device like my PowerTap 2.4SL is exactly the right tool. If used properly I can just adjust my gearing and cadence to maintain a steady power reading, and ignore my speed completely for a nice smooth effort. Unfortunately I didn't do that.
I knew (or should have known) that I averaged 242 watts last time I did the test, and that my target power output should be somewhere in that ballpark. 245 would have been a good target. Unfortunately I started the first lap into the headwind, and took off like a bat out of hell. I felt good, my wattage was large and I was thinking quite highly of myself. I did 265 watts on the first lap, at 22.4 MPH - including a 5 minute stretch with a tailwind where I did 27.4 MPH!
But, the second loop bit me. Somewhere struggling along the long backstretch into the headwind the lactic acid started building up in my legs, and I knew I was in trouble. I fought hard on the second loop, but was angry at myself for f'ing up the pacing. Lap 2 was 239 watts, a drop of 10% over lap 1. Crap... this is supposed to be an even effort - or maybe even a slight negative split. The third lap I knew I was toast, but I left it all out on the island and ended up with a 230 watt average. Here's the final numbers:
Distance: 12.37 mi
Min Max Avg
Power: 0 464 245 watts
Heart: 118 153 146 bpm
Cadence: 56 141 92 rpm
Speed: 14.9 30.6 22.1 mph
245 watts and 22.1 MPH. Compared to last month (242 watts, 22.0 MPH) it seems almost identical. However, since I approached the pacing so badly this month, I really feel like I could have done better. If I had targeted 250 watts, and actually stayed there on the first loop instead of burning out, I feel like I could have held it the whole way. Next month my target wattage for the three loops will be 245, 250, 255.
For those of you doing the math, my FTP changed drastically this time. According to WKO+, my peak 20 minutes (CP20) were the first 20, where I held 255 watts.
FTP = CP20 * 0.95 = 255 * 0.95 = 242 watts.
Last month my FTP was 230 watts, so at first this seems like a great improvement. In reality it's just a side effect of my inconsistent pacing - I had 20 good minutes which make the CP20 artificially high, which I paid for with 10 lousy minutes that brought my CP30 back to almost exactly where it was last month. Pacing, pacing, pacing!