December 22, 2006 6:07am CST
Elements of good running technique Upright posture and a slight forward lean Leaning forward places a runner's center of mass on the front part of the foot, which avoids landing on the heel and facilitates the use of the spring mechanism of the foot. It also makes it easier for the runner to avoid landing the foot in front of the center of mass and the resultant braking effect. Stride rate Most elite runners in the world run at a stride rate of 180 strides per minute regardless of the running distance and the runner's physical build. It has been postulated that human physiology dictates that the 180 stride rate is the most efficent in terms of energy expenditure when running. Most beginning runners have a lower stride rate. This may cause most of the energy to be expended in vertical movement rather than in overcoming the friction of air. Also, low stride rate may also be indicative of overstriding. Using smooth circular leg motion Many people have compared the motion of the legs and feet when running to pendulums. This is incorrect. A pendulum has a natural frequency of motion. For a human leg, this is usually much slower than the frequency of leg motion when running. When one uses a pendulum leg motion for running at a frequency higher than one's legs' natural frequency, the energy expenditure to simply maintain that motion will grow exponentially with respect to frequency. This is very inefficient. Intuitively, this amounts to swinging the leg forward, using muscular power to stop the forward swing of the leg and accelerate it backward, using muscular power to stop the backward swing of the leg and accelerate it forward, ... and so on. In comparison to a pendulum motion, a circular motion is one that preserves the angular momentum of an object revolving around a center. An object moving in a circular orbit will not require any additional energy for continued motion in the absence of friction regardless of the frequency. When running efficiently, the foot motion approximates a smooth circle, capturing as much of the rotational kinetic energy of the foot as possible. An anecdotal example of a good circular running form is that adopted by the typical competitive Kenyan runner. To an observer, Kenyans' running form seem to have a very exagerated motion with high lift of the heel. Many people would postulate that lifting the heels that high would require a lot of muscular power from the hamstring and thus be inefficient. In reality, most of the heel lift is accomplished by the preservation of angular momentum of the feet without the use of muscular power. The high heel lift is an integral part of preserving the circular motion and efficiently preserving the rotation kinetic energy of the feet.