Originally Posted by
merlinextraligh
The example I gave shows why time is a much better metric for volume.
Not really. If you tell me you rode 17 hrs in a week that says nothing about how hard you rode or what the stress on your system would be. That could be a weeks worth of Z1/2 easy base training or, as in your case, a higher percentage of Z3/4 efforts.
Given the variabilities of group versus solo, flat versus climbing, wind speed and direction, the same amount of time, even for a given effort, will produce wide swings in mileage.
Have a look at your annual training stats. I suspect your avg speed doesn't vary much from year to year.
Thus time is a more workable measure, and the reason training plans are almost always done on time rather than mileage.
They are never written based on time only. Like I said, without intensity, time is equally useless as a measure of training stress.