Why does it cost roughly the same effort to run against an inclined treadmill as up a hill of the same inclination? That is neglecting the movement of the legs and the bobbing up and down as we run and the wind resistance. I remember being told in school physics that there is no work done unless a mass is accelerated or raised. To a first approximation, on a treadmill we do not ascend and we do not accelerate. When running up a hill you are going up. So the treadmill should be nearly effortless as you are not raising a weight hence not doing work. Of course it is not effortless so where is my error?