Question About Jumping

Classical Mechanics

Suppose you are standing still and upright, and you decide you want to jump into the air. Why do you have to bend your legs first?

To take advantage of the change in gravitational potential energy To hyper-oxygenate your bloodstream in the denser air beneath, in preparation for physical exertion To store energy in your legs like springs So that work can be done on your equivalent center of mass as you move upward again