roadie77

I think that an answer to this question framed in miles is probably not going to be the best way to go. Kilojoules of energy per kilograms of weight per week would probably be the most detailed way but it would be hard to come up with an actionable plan based on this metric. Hours per week is a pretty good compromise. My gut feeling is most people would get increasing returns on 20 minute power from moderate zone 2 sessions on 5-7 hours a week of training. Diminishing returns from 7-16 hrs per week. Almost nonexistent returns over 16 hrs. Just to clarify, once you've attained whatever fitness level you're going to attain based on 5-7 hours a week of zone 2 you will have to increase either volume, intensity, or both to continue improving.