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Old 11-14-19, 05:20 PM
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wphamilton
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Originally Posted by OBoile
No that isn't what I meant.

Aerodynamic drag is the main source of resistance when cycling (excluding hills***). When running, it is gravity. Yes, there is an aerodynamic component, but it is, proportionally, much smaller than it is with cycling. This should be obvious to anyone who has watched/participated in these sports. There's a reason why elite cyclists can't just ride someone off their wheel and have to attack hard to create an initial gap while runners don't have to do this.
Wind resistance changes far more than gravity. It changes due to wind speed and direction. It changes due to temperature. It changes due to air pressure. It changes due to your CdA. As such, the time to complete a certain distance varies far more when cycling than it does with running. As such, outside of a velodrome, time isn't a very accurate measurement of performance for cycling.

If you want to measure how much work you are doing, running speed works fairly well and is fairly consistent. For cycling, to achieve something similar wrt consistency, you need a power meter. Your day-to-day speed will vary too much to get anything meaningful other than perhaps a long-term trend.

*** cycling up a moderately steep hill is fairly close to running wrt what type/proportion of resistance is slowing you down. That's why grand tours are decided in the mountains. It's also why you see people just fall off the back, unable to maintain the pace of the leaders. It's also why lighter riders tend to be better (whereas pretty much every elite distance runner is small and light). It's also why your times going up a hill will be much more consistent (assuming consistent effort) than your times on flat terrain.
Yes, it is more important at cycling speeds, as I simply stated as a fact originally. I didn't think it required any justification, but OK that you mention the basics there.

What I think you're neglecting here is that even though drag is more important in cycling it still plays a bigger part than you seem to realize in running. 8 0r 10% of his energy overcoming drag in a 5k. Keeping in mind that the runner has twice to three times the drag coefficient of the road cyclist, it becomes significant at lower speeds.

Wind direction, wind speed, and the rest of that plays just as much a part for the runner. So going strictly by pace you could be off by 10% - not important, perhaps, but no less important than needing precise power in cycling rather than estimating to within, say, 10%. It's funny, to me, the disparate "conventional" opinions between the two sports, utterly convinced that a power meter is a necessary training tool in cycling and equally convinced that it's irrelevant in running, even though objectively the reasons for those firm convictions are validly applied to either sport.

I'm more in line with @Doge - it's a more specific need than most people realize - but if a cyclist believes that he really needs a power meter to train properly, then he's not really training "properly" if he's running without one.
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