This question already has an answer here:
While it is very hard and energy-consuming to run a marathon, covering the same distance by bike is doable by most people. Where exactly does the gain come from?
Assuming for simplicity that we are on a flat surface, all the expended energy eventually dissipates, i. e. is used to produce work against friction. I can see the following possible explanations of why walking/running could lead to less efficient setup:
- when running, at each step one needs to lift their center of mass, turning the energy into potential energy, which is then dissipated;
- when the front foot reaches the ground, it moves in the forward direction until friction stops it, dissipating its kinetic energy;
- our joints are just less suited for walking than for spinning peddles and dissipate more energy doing that.
So, I would like to know which of these reasons really contribute/are dominant? Or maybe there are some other reasons I did not think of? Are there some fundamental obstructions for walking to be more efficient, or is it just an "engineering" issue?