Running on Egg Shells or Hot Coals

Huh? What does this mean? You have probably heard many coaches say that elite runners run as if they are running on hot coals or on top of egg shells (that you don't want to break). What does this really mean besides the obvious of picking your feet up really fast. It also means that you want to minimize the force you push with your feet into the ground.

If you have the correct form, you should no longer be supplying a force with your feet on the ground. If you do, you are wasting energy. You should be picking your feet up and actively moving them forward, then passively letting them fall to the ground (when they are below or slightly in front of you) and once on the ground, you should minimize the time that they are on the ground and not allow them to move too far behind you. In other words, all of the active motion (with your muscles) occurs when your feet are off the ground. With this, you will only have the weight of your body on your feet, and if you are light enough, you will not crack those eggs. (Elite runners run this way, but additionally they can pick their feet up much, much, much faster than you).