HUMANS ARE BUILDT TO RUN WITH PHYSICS
By CEO Robert Forster, PT
Author:
Healthy Running Step by Step
We humans are movement machines. Evolution built our bodies to run, walk, and stride for long distances at fast speeds, probably to track down animals for dinner — and run from them when they have other ideas. Compared to our slower primate cousins, human bodies have a large number of running-friendly features: shorter arms to balance the cyclic movement of the legs; lighter lower legs and thicker hips, which allow the leg to swing with little effort like a pendulum; bigger, more complex feet, to absorb shock; and thicker lumbar vertebrae, also to absorb greater shock forces. In addition, we have a built-in economy of motion that turns our muscles, tendons, and connective tissue into natural springs, slings, and pendulums that effectively store energy during the gait cycle, then return it on the next step.
So if we are natural runners, why do we so often get hurt doing it? The trouble is that the sedentary lifestyle of the modern world has basically ruined our ability to exploit our gifts. Unburdened of the need to hunt and chase and carry, we don’t move enough and have become soft. As with everything related to the body, it’s a case of “use it or lose it.” Even though you run one hour a day, in the modern world that means your body is lying fallow 23 hours a day. We have become so removed from our natural movement patterns that our bodies are a mess. All that sitting has left our hips tight, our hamstrings and calves shortened, and our glutes weak. Our bodies have forgotten how to move the right way.
To reawaken our distant memories of correct movement, you’ll have to relearn how to do one of the most natural activities: running.
Some people may recoil at that. Learn how to run — when we were born that way? Seems crazy, right? But the reality is that natural running in the modern era is an acquired skill, no different than a beginning golfer taking golf lessons, a tennis novice taking tennis lessons, a rookie guitar player taking guitar lessons.
As far as your corrupted-by-the-modern-world body is concerned, running the way that nature intended actually requires increased strength and new neurological patterns. If you want to run correctly and injury-free, you must drop the notion that because you ran as a kid –- or even do a marathon a month now –- you already know how to run –- and don’t need lessons. Wrong! You know about as much about running as a high school freshman does about throwing a javelin for the first time. He knows how to throw a stick, but it’s not going to go very far without learning the specifics of good technique. But it isn’t difficult. In fact, with a few simple cues and a basic understanding of physics, you can take advantage of the evolutionary gifts bestowed upon you to run efficiently and injury-free.
Those who have studied running techniques even briefly have most likely heard of the Chi Running, Pose, and barefoot running methods, which as a group share a bias against the heel strike –- with which I don’t disagree. People were not designed to land on their heels. The heel strike gives you a “braking” effect — that is, it slows you down -– and a potential “breaking” effect -– meaning that it transmits far too much shock up your leg and into your knee, hip, and spinal joints and can lead to injury.
Does this mean that I’m completely in sync with Chi, Pose, and barefoot advocates? Not necessarily. I think they tend to make running more complicated than it needs to be and don’t fully understand how to exploit all of the built-in efficiencies of the human body. My approach to proper running technique focuses on what happens to the leg at the joints of the pelvis, hip, and knee, and where your foot hits the ground in reference to your center of gravity. When you use these joints properly, the foot strike takes care of itself.
Running with the Laws of Physics: Slings, Springs, and Pendulums
To fully understand the whys of proper running mechanics and how to use your body correctly when running, we have to talk a little about a few simple laws of physics:
Momentum
A body in motion tends to stay in motion un- less some force acts to impede its progress. Every time your foot hits the ground, the foot-ground reaction acts to slow you down. Every millimeter that your foot strikes the ground in front of your center of gravity further increases the braking effect on your forward momentum. The center of gravity of your body is the center of your weight distribution, the point where your body would teeter on a focal point if you were lying horizontal in space. This spot is located in back of the pelvis. Left to own devices, all of us overstride –- that is, land way too far in front of a line dropped from the center of gravity to the ground below us. This not only wastes energy as we try to regain forward momentum, but it causes us to land on the heel of the out-stretched leg and leads to injury from the excessive shock forces. So when it comes to foot strike, it is not which part of your foot hits the ground first, it’s where your foot hits the ground in relationship to your center of gravity that will either minimize ground reaction or amplify it — that is, either slow you down or let you move forward more easily with less effort. A higher knee rise and shorter steps ensure that your foot will hit the ground more directly under your hips.
Slings and Springs
The human body is made of sinewy connective tissues that stretch under the load of our body weight when we hit the ground. The stretched tissues store what is called potential energy; just like a rubber band that snaps back to its original form, the rebounding tendons, ligaments, and fascia give back that stored energy and provide much of the forces needed to propel us forward. If we use our body in the right way, these re-bounding tissues can unburden the muscles of some of the work and save energy, allowing you to run farther and faster. You harness this elastic energy by keeping your connective tissues flexible and running with high knees to keep the leg swinging backward when it hits the ground.
Pendulums
A pendulum is a line, weighted at the bottom, which swings in an arc from a fixed anchor point above. It requires very little energy at the beginning of the movement to stay in motion. The most efficient way for the extremities to swing through the air is for them to act like pendulums. Pendulums require gravity to keep them moving because when they swing forward, they hold stored potential energy because gravity wants to swing them back to the bottom of the arc. With little muscular energy at the start of the arm and leg swing, your extremities will return to their place of origin and save muscle energy.
Using a high knee in running serves several energy-efficiency purposes. First, it allows us the time needed to be sure the pendulum has finished its forward swing and is moving backward when your foot hits the ground. Second, achieving a high knee rise automatically brings your heel closer to your butt and thus shortens the length of the pendulum that is your leg. Physics teaches us that shortening the swinging lever reduces the energy needed to swing it through the air and therefore reduces the work your hip flexors need to do to pull your leg forward.
Last, as the leg swings through the air with a high knee rise and the lower leg is naturally pulled up closer to your butt, it reduces the resistance of the wind as you run. It is not only beneficial when there is a headwind, but even on a calm day your body has to push itself through the standing air, and this energy savings adds up over longer distances.
