Originally Posted by
RChung
Well, for one thing, you can do pretty precise drag estimation with total power but we haven't been able to get consistent results with drag estimation using power meters that double one-side power. There are other reasons but that's a pretty clear one since many riders who've been doing structured training for a few years have plateau'd on their training gains and if they want to get faster they have to pay more attention to drag reduction.
Drag reduction is going to help in going faster no matter how you measure power. Using total power does make the estimation of drag coefficients more accurate, but unless you're in a wind tunnel the variation in measuring outside is going to introduce huge errors in the results anyway.
And even if you assume some skew in power numbers from using left power doubled instead of total power such that the resulting numbers are less accurate, the relative drag test results are going to be the same - lower drag positions will still have lower estimated drag coefficients. There will just be another unknown fudge factor scaled into the results. As long as the power results are consistent, you'll get consistent results from drag estimation.
As for L/R balance and injury, I had a little sciatica problem a few years ago that resulted in a huge bilateral imbalance. My right foot flopped, I could only walk upstairs by taking a step with my left then dragging my right up, I couldn't push down with any force on the downstroke on that side, etc. -- and I had a PowerTap. Over the course of six months or maybe longer I just kept riding and eventually my (total) power crept back up to my previous level. I have no idea what my exact L/R balance was before or what it is now but I know that my total power is back up to pre-injury level. So, although I disagree with you that total power isn't more useful than doubling one-sided power, I'll agree with you that knowing L/R balance isn't more useful than not knowing it.
[Edit] Which is not to say that I don't think there's a place for the Stages. I think it can be a good gateway drug.
No, actually I think that knowing the L/R balance can be useful. But if you don't know what it is, I'm saying there's absolutely no practical difference in using total power vs. left power doubled for training.