Why is standing still easier than walking?

Question

Both the works basically push force into the ground.So why does walking require more work?

Answer 1

Walking requires raising and lowering the centre of gravity, as well as moving the limbs. Both of these require muscles to contract and extend and use energy. If the muscles were perfect springs then the energy stored during contraction could be fully recovered during extension. No energy would be lost. But they are not perfect springs - some energy is always lost during the cycle of contraction/extension.

Energy is also used when muscles are holding things up, not doing any physical work (= force x distance). This is explained in the following links :

Why does holding something up cost energy while no work is being done?

Does energy expenditure require movement?