ABD Indoor TT#2
January 27, 2008 – Winfield, IL
Cat 4 – 17th – 16:28.50
298 watts – 22.6 MPH
When my sister was really young, she came up with her own form of addition. 1+1 was 11. 2+3 was 23. She thought it was fun, even though it wasn’t real math. After having used Computrainers and power meters the past few years, I have come to realize that power readings don’t always add up the way you think they would.
I was really happy when I left the second ABD Indoor TT on Sunday. After chalking up a DNF during the first one because of my sinus infection, I had been aiming for a decent performance. Despite a time that I thought was a little slow for me, I was pretty jacked about my power output.
The second TT of the series was a “rolling” 10K Computrainer course that definitely throws your momentum. It’s much different than racing on hills outside. I was in a fairly even heat with seven other riders. During the race, I mostly focused on my power output to keep an even pace. I worked the hills and either gained or caught up with other riders. On the downhills, the others hammered while I remained consistent. I felt pretty good throughout the race, but my legs were a little tight. I ended up with a time of 16:28, but with an average power output of 316 watts. I thought it was a little high, so I did a little power analysis when I got home.
According to my Powertap, my average power was 298 watts with an average HR of 184 bpm. This was right in line with where my LT intervals have been. Here’s where the math gets weird. The average power on the Computrainer during the race was about a 6% HIGHER than my Powertap. However, the power readings on my Computrainer at home are about 7% LOWER than my Powertap. And, my HR readings in either setting if I out out the same wattage on my Powertap. Weird.
There a lots of different variables than affect Computrainer calibration, and then there’s the whole debate over which is more accurate–the Powertap or the Computrainer. Considering my background ia in biochemistry and not engineering, I won’t even touch that one. I just can’t wait to get outside and start racing. I’m still looking foward the the next few indoor TTs, but riding indoors is starting to get to me. Ironically, trying to figure out the math on my power and HR readings while I’m biking actually helps make the time go faster.
When I looked at my results from last year, I noticed I got the same time yet my power readings were 20 watts lower on the Powertap. Yep, this math doesn’t make any sense.