Legs like the Oars in a Boat
A good way to illustrate why a posterior driven gait is a more efficient way of walking is to think of the analogy of a boat on the water. If you have an oar and wish to paddle the boat you won't get very far by just reaching the paddle forward and dropping it in the water. Instead, you need to drive the oar into the water and pull backwards in order to propel the boat forward. The legs may be thought of in the same way: in order to propel your body forward, you need to drive the standing leg into the ground and then pull that leg backwards. It's helpful to think of the motion from coming from the back of the knee or thigh rather than the foot, because if the focus is on the foot, there may be a tendency to bend from the knee. To extend the metaphor, your oar in the boat will not be very effective if it's floppy like a spaghetti noodle and your leg is more effective if the whole leg is sturdy and the knee doesn't collapse. Try walking thinking of the legs like oars in a boat.
