I did that on stair steppers as well for a while. It's tough on your feet and calves.
I recall reading somewhere, perhaps in his encyclopedia, that Arnold used to work his calves by driving his feet into beach sand and pushing off with his calves. He said after a few hours his calves were blown up like balloons. You can also do this just walking on a sidewalk. You push off with your calves. It takes concentration and I just walk normally now. These things just pump blood into your calves and make you feel like they are bigger.