I had a big argument at the pub about the stair machine being easier than actual stairs, and all the people there disagreed, saying that the only difference is air resistance? Are they kidding?
My point was that, as the stairs are moving in the same direction as you, you are exerting less force to maintain you torso's position; i.e. $mg = F_{\text{stair}} + F_{\text{leg}}$ (when climbing a stationary stair $F_{\text{leg}} = mg$)
The only time where this wouldn't be true is if the stair was stationary, you push yourself up, then after moving your body weight up, the stair moves down and becomes stationary again. But otherwise, the stair and your legs are moving in the same direction and the force (work?) required to work against gravity to push yourself up against the stair is less. Proof in the pudding is that, if the stairs move faster, the force exerted per stair is less
Is there a better way to explain this? It was infuriating. I think it has something to do with a work balance equation, but a figure would be better.