Originally Posted by spclark

Funny that.

I can work an hour (or longer) trainer session into my daily routine several times a week yet it takes me vastly more effort and planning maybe to get in a two-hour outdoor ride once every couple of weeks, if I'm lucky!

Acquiring a trainer (wheel-on Wahoo) then making a habit of using it increased my cycling 'activities' 1,000% since last summer. Up until the weather changed where I am to make outdoor biking fun (I don't like being cold or wet, or having to wash my bikes after normal road useage) I'd logged close to 600 miles ridden, mostly to Rouvy. By comparison, even with better weather, my outdoor riding so far this year has been maybe 30-35 miles in three sessions of about an hour's length.

To the OP, I'd say yes it is good exercise riding a bicycle. But it's not everything proper exercise might be, at least according to some. Weight training also helps (something I don't do) and even walking briskly I believe does more to keep a body functioning as it should without the inherent risks of coping with vehicular traffic if you prefer road biking to biking activities where other risks predominate. Swimming's also beneficial while demanding more in the way of facilities, either indoors or out.