Many people believe that you are born with either good or bad running form, and that there is little that you can do to change it. We have all seen "natural runners," and envy their fluidity and grace. But by knowing a little bit about the physics of running and trying to adopt some of the common traits of all "good" runners, it is possible to improve on what you're stuck with.
Physics: Your body's center of gravity is in your midsection. Any force that is applied to the ground in front of this center gravity acts as a braking force to your forward movement. Picture a runner with an exagerated running stride. Every time he plants his heel forward of his body, he applies a braking force, slowing himself down. In addition, before he is able to apply force to the ground and move his body forward for the next stride, he must wait until his body has moved directly over his foot. If you look at the form of most good runners, you will see that their feet strike the ground directly beneath their body. Running with this shortened stride is also characterized by a "mid-foot" strike (not on the heel, not on the toes, but at about the ball of the foot) and a high cadence, or "quick feet."
Now, having said all of this, don't watch me run. My wife Sue says that rather than run, I "lumber." But she also says I've gotten much better. This is my "System Checklist" that I use to critique my running form as I run. I start with my head and work down my body.
Head: Neutral position, don't look or down. Try to think of centering your head on your shoulders. Face muscles are relaxed and loose. Try to feel your facing bouncing with each stride. Sunglasses and a hat always help.
Shoulders: Relaxed, loose, but not "hunched forward." Think of "running proud" with your shoulders back, but don't try to actually pull them back. This creates muscle tension and is a waste of energy. Any forward lean must be supported by your lower back, changes your center of gravity, and results in wasted energy.
Arms: Any excessive side to side motion, or swinging across your body is a waste of energy. Try to think of everything moving in a straight line and in one direction: forward. Keep your elbows in and bring your arms up in a straight motion. Hands should be relaxed and loosely cupped.
Hips: Very important. This is the home of your center of gravity. Try to run with your hips forward. Pretend as if you have a rope tied around your waist and someone is pulling you forward with it.
Feet: I changed from a heel striker to a mid-foot striker and I'm convinced that this has kept me injury free. Try it if you want, but just beware. But regardless of how you plant your foot, you can try to plant it directly under your body and your center of gravity. Try running with a quick cadence of 88-90+. Simply count the number of times that your left foot strikes the ground in one minute. It will feel strange at first, but if you practice enough it will become second nature. Also, think "quick feet." Try to make as short as possible the time that your foot is on the ground. I've gone from 82 rpm at my IM pace to 90+. One of the most satisfactory compliments I've ever gotten in a race is when a spectator said "good cadence" to me at mile 25.5 at IM California. I spent a lot of time working on this and its nice to see it paid off.
Miscellaneous: Limit your vertical oscillation: run forward, not up and down. Try this trick: run with a hat and pull the brim down to just over you eyes, so that it takes up half of your vision. Run, look forward, and try to keep the brim of your hat steady on the horizon.
Count your cadence: just like counting your strokes in the pool, I have found that the act of counting my cadence on the run focuses my mind on my running form. Every 5 minutes or so I'll do my little system check above, and then count my cadence. It keeps me in the game and prevents my mind from wandering.
Not good runner, but I'm trying.