RE: A: Should you climb stairs two steps at a time to save energy?

[quantumdeveloper]

I think the main reason for single step being less efficient is friction.
Every time you step on the ground you loose most of the kinetic energy that pushes your leg towards the ground (you can see that your leg doesn't bounce up again like a rubber ball).
So when you hit the ground only half of the time you loose only half this energy. So taking double steps is more efficient.