Sunday, 16 December 2012

December's 20 minute power test - weighed and measured!

After 4 weeks of turbo time it was eventually time to complete another 20 minute power test to see if I had made any improvement. I tried to control as many variables as possible; so I used the same bike and powertap on the same turbo, with the same pre-ride calibration and I even used the same kitchen.

Before I started I didn't feel very motivated but I know that it's pointless doing interval sessions to improve power unless I test myself regularly to see if they're actually working. If they aren't I need to know so that I can change my routine.

Anyway, the headline is that my 20 minute power is 331W today compared to 322W 4 weeks ago. This 9W equates to a rise of roughly 2.8% which is well above what I had expected. I was hoping for a 1% improvement per month which would get me to my 345W target by May 2013. This equates to a 14 sec improvement over a 10 mile TT.

Here's the plot from today's power test (Red = HR, Black = power):

After a decent warm-up including a 320W power test to make sure everything was OK, I had a poor start and went off too hard and had to wind myself back, but I was settled in after a minute or so. I noticed that I was continually nudging above my 325W target and after 10 minutes I had averaged 328W. The last 10 minutes were hard and sweaty with a couple of weak periods but not the big crash I had previously experienced around 17 minutes.

Below is a comparison of the 2 power tests showing December's test (Red line) compared to November's (Blue). The obvious differences are the stronger start and the improved performance towards the end when I didn't crash in the Dec version. Dec looks much more under control.

Comparing HR across the 2 sessions looks like this:

The difference between HRs at the start of the session is due to slightly different warm-ups and is maintained until around 12 minutes, but at the end the HR traces are almost identical. This is interesting because I use power to pace myself during 20 minute tests but my limit seems to be HR-related. Without a powermeter I'd certainly start too hard and achieve a lower average power over the 20 min test. Average cadence for the 2 sessions is very similar too at 84 rpm for Nov and 86 rpm for Dec.

So what have I learned?
  • At the moment I haven't learned anything. 2 data points are not conclusive but I did feel a lot better on today's test so I'm assuming that the power improvement is genuine; I just need more data to prove it. I have seen how my performance can vary from day to day so it may just be that I was weak on the last test and strong today but that I haven't made any actual improvement. Time will tell.
  • My work-outs over the last 4 weeks have targetted power Zones 4 and 5 so I would expect to see some improvement in a Zone 5 power test (which is what a 20 minute test is) and I have purposely avoided harder intervals. However, this doesn't mean that these were the best intervals; I may have showed a higher 20 minute power increase just riding for an hour at 90%FTP for 2 hours a day.
  • I will need to increase my work-outs to reflect the increased FTP and to continue to provide an impetus for my body to adapt to the increased stress. Again, this is the reason regular testing is essential.

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