Friday, November 12, 2010

Computrainer Power/Efficiency

I usually spend a few hours a week reading articles, blog posts and other materials.  One thing that really interests me is the whole concept of power meters.

Earlier this year I purchased a 10yr old Computrainer.  After updating the handlebar controller chip and replacing a few other parts, I now have power when training indoors! 

I can see some good progress on my power output, using a 30 minute time trial on a flat course (10 miles). I have gone up from 194 watts to 214 after 6 weeks, and after 3 months I managed complete 30minutes at 245!  This is pretty amazing, for the last test I was hoping for something in the 220’s.  So that works out to around a 25% increase in 10 weeks, a great effort. 


Whilst my power is going up, my riding efficiency is something that I have to work on.

The computrainer software has a large amount of data available, both on screen while you are riding, and of course on the computer after a workout has been completed. 
Some of the more interesting statistics are :-

  • left/right power split – which helps to make sure you are in balance
  • spinscan value – how efficient or even each pedal stroke is
  • ATA – average torque angle. a measure of where the most power is generated – in degrees from top dead center.  This is something that I am working on understanding

It is obvious that you want the left/right split to be an even 50/50 – I am right around there most of the time, sometimes it drops 48/52 for a while but for the most part I seem evenly balanced.

Spinscan and the ATA numbers are something that I have to work on.  The idea is to get the spinscan numbers as high as possible, with 100 being perfect (but practically impossible, unless you are an electric motor). 

The question that I had was is:  what is a good/bad/average/excellent spinscan numbers?

For most of my recent training – I have been in the low-mid 60’s and a few times in the 70’s.  it is generally trending upwards, but I still didn’t know if a 65 is good or not.  I found an article on YouTube (here) which suggested the following for both spinscan and ATA:-


So – I am a C in ATA numbers, and lower (a D or E) for Spinscan.  This gives me a new short-term goals to work on for the off season.  I’d like to improve my efficiency before/during base training over the winter.

I’ve also read a lot of articles about power on the bike – and almost all of them refer to the “bible” – “Training and Racing with a Power Meter” by Hunter Allen and Andrew Coggan. 

powermeter-bible2 I am really looking forward to reading this and getting a deep understanding of the whole power concept.  I want to understand as much as I can before I purchase a power meter for the bike.  I am considering waiting for Garmin to release the Vector unless is can somehow find the $$$ to purchase one sooner (not very likely).

Before I start reading this book – I am still working on finishing “Iron Fit” by  Don Fink.


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