A good running style does not guarantee great running performances, but poor running style certainly sabotages them.
To analyze and improve your running style, assess the major moving parts of the body as they relate to running as fast and as smoothly as possible.
When you run in a straight line, your successive foot placements should be parallel to each other (or very nearly so). This will reduce the rotation or twisting of the ankles and knees and will help prevent shortening of your stride due to turning out of the foot.
Because the hip, knee, and ankle joints all must bear the severe stresses and impact of running, you should always try to concentrate on preventing any twisting or sideways motion and keep the feet and legs moving directly forward.
Improved ankle flexibility has a major payoff in stride length. African runners seem to have the best ankle flexibility, perhaps because they grew up running barefoot as children. Their style shows the knee of the supporting leg well in front of the ankle, which gives the foot a greater range of motion throughout the pushoff phase of running.
The longer the heel is left in contact with the ground while the knee moves forward, the greater the pre-stretch of the calf muscles. This increases both power and stride length, as a pre-stretched muscle generates greater contractile force.
Use appropriate knee lift.
Sprinting requires high knee lift; marathon running does not. Distance runners should avoid dramatic knee lift, because energy that should be directed to forward movement is wasted on up-and-down motion. Find a comfortable and appropriate degree of knee lift.
Stretch and strengthen the major muscle groups.
The pelvis accommodates large muscles, which generate the powerful forward thrust of the pushoff foot as well as the thrust of the forward-striding leg. The muscles that stabilize the hip against too much rotation must be especially strong to prevent injury.
Lack of hip-joint mobility limits stride length and often results in a forward lean of the torso. By increasing your hip flexibility, you can run with a more vertical and energy-efficient style.