The normal method of human locomotion is walking, or running if we are in a hurry. The biomechanics are still the same.
The human body’s centre of gravity is around about the middle of the pelvis. The more this point moves up and down relative to gravity, the more energy is expended. Walking minimises this work while maximising the distance travelled. It does this by causing us to continuously fall forward while providing a leading leg to bring us back up again. If we didn’t do this, we would spend our whole lives either standing on one leg, or collapsed in a heap on the floor
There is a spiritual analogy here, of course. In our spiritual life, we fall continuously into sin. Concupiscence is a kind of gravity. We can either put our other leg forward to rescue our fall and ready ourselves for another step, or we can collapse in a heap.
Our other leg is given to us by Christ’s forgiveness. The Cross makes a perfect crutch.
A Christian must walk the walk as well as talk the talk.