Originally Posted by
DrIsotope
Except that other that between the green and checkered flags, speed is a meaningless metric. I could draft a van all day and do a century at a 30mph average. Or I could just ride downhill. Or one day the wind is in my face and the other is at my back.
Speed is in not always indicative of effort. A power meter shows work done and ignores speed altogether. Anyone who has ever ridden up a hill knows it can take every bit as much work to climb a hill at 7mph as to cruise on flat ground at +20mph.
A power meter is one way to eliminate a lot of variables.
So basically, the power meter is a method to confirm what everyone already knows? Everyone also knows you can control for this by repeating the same course under similar conditions. and comparing times.
It's a useful tool for many, but clearly not a necessity for effective training.