Pedaling Index
My average PI falls right at 24%, with the maximum I've ever had being in the 65% range (forget the exact number). I've played around with different pedaling styles if for no other reason than to see what affects the number. Overall, I'm not sure I think that it's a very useful measurement. What I've found is that to increase the index, I in effect have to decrease the force applied on the down stroke in order to keep the overall stroke more consistent with respect to force. This doesn't seem advantageous to me as I believe that no normal human will ever be strong enough either on the pulling part of the stroke, or the cross-over strokes, to be able to apply "natural" force on the down stroke while maintaining consistency throughout. There are many times, expecially when hammering up a hill (which I have a lot of around here) that the index is reading as low as 11%.
Power Unit
You'll find a lot of posts on this forum regarding the accuracy/inaccuracy of the polar power meter. I've done several studies personally both with regard to the accuracy, as well as to set-up on the bike to see what affects the reading and/or how to make it more consistent.
In short, I agree with the other poster, I've been very happy with the meter, and am convinced that it's accurate within tolerable limits, especially if you're trying to track improvement rather than absolute power values. In either case of use however, I believe the meter to be very useful.
Regarding the difficulty of using it on a trainer, there IS some issue here. The vibration created by a trainer definite affect on the power readout (I suspect by affect the chain tension sensor). What I've found through tests however, is that this affect seems to be concentrated around certain frequencies.
FWIW, it seems that on MY trainer anyway, the vibration starts to have a detrimental effect at wheel speeds equal to 28-30 mph and up.
What I've done to deal with the issue is to increase the resistance on the trainer dramatically (almost maxed out). This in turn allows me to generate x power at much lower wheel speeds. The lower wheel speeds create less and/or a different frequency vibration. As a result of doing this, I get the same consistency, and very good correlation with road results (which was an added benefit.
As an example, (and you can verify this using tools at analyticcycling.com, powertap meters, etc. )
It takes a considerable amount of power to maintain a speed of 16 mph on a 3% grade (as opposed to flat road). The actual power dependant upon weight, air resistance, rolling resistance, etc. For me, that number falls into the ~290 watt range. Not only are these the numbers I get while riding on the road, these are also very close to the numbers I get while generating the same speed on a trainer. In addition to that, I've found that my heart rate (YES, I KNOW IT CAN VARY WITH CONDITIONS) to be very close in either situation. Perceived effort is close enough that I can't tell the difference. The power reading in this test isn't affected by more than 5-8 watts regardless of what gear I use to generate the power.
Considering all that, I believe I've found at least ONE way, or at least one riding conditioning in which not only are the results repeatable, they also correlate very well with road riding conditions. Being that I've increased the resistance on the trainer, I've yet to do any testing at much greater wheel speeds (greater than 30 mph) since that requires greater power than I generally exercise at on a trainer.
I HAVE however, generated increasing speeds a few times (since adjusting) just to see the affect on the power reading. What I see is essentially what I saw before. At some point in the 30 mph area, the vibration reaches a frequency at which the readings become relatively inconsistent, and at a speed just a little faster, the readings start DECREASING. Strangely enough, this seems to correlate with the vibration you feel on a trainer (mine actually feels to smooth out at the same time).
If anyone else has similar results and/or has tried similar things, I'd love to hear about them.
John
