why is going up the stairs (or up a hill) so much more physically intensive?

Question

I am not very fit, but I do walk a lot. However when I go up 3 flights of stairs I am out of breath. How come?

In: 0

Answer 1

mgh…

When you go upstairs you are converting the chemical energy of your body into potential energy. If you are 100kg, and each flight is about 3.3333m then you are increasing your potential energy by 10kJ. Your body is only about 25% efficient in energy conversion, so you are actually consuming around 40kJ (about enough energy to increase 4l of water 10C).