Riding a bike isn't like walking or running. A completely untrained individual should be able to jump on a bike and bang out 10 miles at an easy pace. A trained but untrained ( winter lay-off) individual ought to be able to do 20. The only difference would be the time it takes. If you wanted to do a much longer commute at the same average speed as the regular one that would have to be worked up to. The effort, not the distance. I don't at the moment, but I should and most of us should, incorporate some additional cardio and even some weight training into our overall fitness plan. I've signed up for this program that will pay 40% of my health club membership every month that I go at least 3x/wk. Its a nice gym and I couldn't normally justify the $40/mo , but its only a block from home and is open 24/7.

H