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.

Weigh-in

For the last 3 days my weight averaged 75kgs. Using the same power recorded at the last 20 min power test, this predicts a 60 min PWR of 4.09, up from 4.03 at the weekend (obviously all due to the reduction in recorded weight!) which is a 1.5% improvement*.

*The reality is more likely to be that my recorded weight last weekend was too high as my activity and diet is unlikely to have resulted in a 0.9kg weight loss. Using the 3500kCals per lb guestimate of weight reduction, I'd have had to have used an additional 6900kCals to drop the weight, which I haven't, so such small changes are likely to be 'noise' and may have been caused by having a fuller stomach, being better hydrated or having a fuller bladder rather than any real weight loss. This is why I'm taking a longer-term view of the power and weight in my target.

2x20 at FTP+

Tonight's Turbo Trainer session was a 2 x 20 min at FTP (target 306W) with 10 mins warm-up and 10 mins between the intervals. I felt OK for the first one (average 307W achieved) and had enough on the second to surge at the end (average 313W achieved). Again, it was a horrible hard and sweaty session and one I was pleased to get off the turbo at the end of. The 66 minutes went very quickly though.

Here's the trace showing a poor start to the first session (bike faff) and then a lot of power to try to get back to a 306W average. As I was above target towards the end of the first session I backed-off. The second session shows a big increase in power output from around 17 minutes. Black line = power. Red line = HR.

Power-to-weight

Fresh off the scales this morning I weighed in at 75.9kgs (3.9kgs above my target weight). Obviously a single snap-shot figure means little but it is the start of a more regular weigh-in so I can track my performance towards my target weight.

Using my 20 min power figure and 75.9kgs gives me a 20 min power-to-weight (PWR) of 4.24W/kg. My target figure is 4.79 so I need to generate a 13% improvement in 6 months (half of which will be weight reduction and half will be power increase).

Using an estimate of my 60 min power (95% of 20 min power) gives me a 60 min PWR of 4.03W/kg with a target of 4.55.

Considering I made no improvements in power in the last year and put on a couple of kgs despite regular training and frequent racing, this might be a bit more of a challenge that I originally thought!