In my Friday posts, I discussed the concept of acceleration/gliding (ACG) that is taught by Jeff Galloway in his book Running Until You're 100. I thought I would briefly explain the science behind gliding. If you're not into science, feel free to skip this post.
Let's assume that you're running at your desired pace. You have stored in your body energy that is due to your movement. This energy is known as kinetic-energy. If you finish your run and quickly stop, the kinetic-energy will go to 0 because you have no movement. The energy that was in your body, however, has to go somewhere; it doesn't just go "poof" and disappear into thin air. Your body absorbs the energy as heat, and you probably begin to sweat. In effect, you paid a price for that energy by applying stress to your body to get it to move at your desired pace, and then you waste it by quickly stopping, causing the energy to be dissipated in the form of heat. That isn't a very efficient way to run.
Jeff Galloway is suggesting that instead of stopping quickly, or even going quickly to a slower pace, you take a few steps to gradually slow down and thus allow your kinetic energy to be dissipated in the form of forward movement of your body instead of heat in your body. This is a more efficient method of running, and that means that you'll go your distance with less effort.
Now, let's look at it from another perspective. Sir Issac Newton, in the year 1687, published three laws that describe motion. His first law states that "A body at rest remains at rest, and a body in motion continues to move in a straight line with a constant speed unless and until an external unbalanced force acts upon it." In other words, a body in motion wants to stay in motion, and a body at rest wants to stay at rest. Newton's first law is also called the Law of Inertia. This is the reason why, if your car stops quickly, your body tries to continue moving until it is restrained by your shoulder belt, or if you're not wearing a belt the dashboard and windshield. It is also the reason why you are pulled back into your seat when your car quickly accelerates from a semaphore light. If you are running and quickly stop, your body wants to continue moving forward.
Jeff is suggesting that we take advantage of your body wanting to continue moving at your faster pace, the momentum of your body, and let that momentum pull you forward until the kinetic energy is dissipated. You do this by taking a few steps to slow down to a stop instead of quickly stopping.