The only thing I do, aside from yard work and various house repairs, is mountain bike riding (on trails). I really only ride like once a week. Been doing it for over a year, and I have definitely increased my strength and stamina. Two weeks ago I went on a ride of sufficient length that brought me near the limit of my ability, muscle-wise. I actually got cramps near the end. Did not ride last week. Yesterday I took a little ride of about 12-15 miles, that was mostly street, just to remind my muscles about riding. I am planning a nice longish ride tomorrow (Labor Day) on some local trails that should be a butt-kicker. I love riding. Wish I could do it multiple times a week, but that's just not realistic.