This is a particularly critical part of running technique, because if you don't get this piece right, several other pieces become impossible.
Almost every runner lands with the foot out in front of the body. This is a single biggest problem with most runners technique. From the position this runner's end, he cannot possibly create propulsion. In this position, the runner cannot effectively pull himself forward, one must wait until he coasts forward to this position until his body is over his foot. This coast time causes a number of problems. First, notice that the runner's center of mass represented by the square at hip level travels upward on an arc around the position of the foot strike and not horizontally. So the energy cost of vertical displacement will be considerable.
As discussed earlier, this also increases the energy cost of support requiring greater energy expenditure upon landing. This foot strike placement also causes significant braking. Slowing running speed of foot strike and requiring significant energy to re-accelerate on every stride. The energy from the runner's last stride carries his body forward from the position here to the position here. Energy from momentum is lost in the process. An additional energy must be expanded to re-accelerate the runner backup to speed. An out in front foot strike placement also reduces energy returned from elastic recoil. Contact time between the feet in ground needs to be minimized to make the best use of elastic recoil.
The coast time required for the runner's body to move up and over his foot placement allows plenty of time for the energy stored at foot strike to dissipate before it can be released at push-off. The energy cost to balance is also increased with this foot strike position. Try balancing yourself on one foot with that foot six inches in front of your body, pretty tough huh? This foot strike placement also dramatically increases impact stress and injury risk. When the foot hits the ground, a runner's center of mass is moving diagonally forward and down. An out in front foot strike position puts the leg almost in a direct line with the body's motion. So that it will absorb the greatest amount of impact stress.
Efficient runners land with the foot almost directly beneath their center of mass, or their hips. This allows a quicker and more horizontal push-off minimizing the energy cost of the vertical displacement and support and maximizing the energy returned from elastic recoil. With the foot directly beneath the runner, momentum is carried through to the next stride efficiently, minimizing braking and the energy cost of acceleration. Landing with the foot and leg exactly in the push-off position, minimizes contact time between the feet and the ground allowing maximum return of propulsion from elastic recoil. Foot strike and push-off become a single moment instead of a landing, glide and then a push-off.
A runner with this foot strike placement requires very little energy for balance. Finally, landing with a foot strike directly beneath the body maximizes the angle of deflection. Impact becomes a glancing blow, minimizing stress to the tissues and effectively carrying momentum forward without braking.
The most effective way to learn optimal foot strike placement is a drill called, Running in Place. Without forward momentum from the previous stride available to waste, a runner has to keep his foot strike directly beneath his center of mass. Alternately, shift your weight from one foot to the other, simulating running but without moving forward. With one leg up directly beneath the hips, just a few inches at first while bouncing on the other, establish a quick rhythm. As you lift your legs in this drill the knee moves slightly forward and the heel move slightly backward. Lift the leg until the lower leg is parallel to the ground with the knee as far in front of the body as the heel is behind it.
Notice that during this drill, your feet always hit the ground directly underneath your hips. Try to this drill with the foot strike that is six inches in front of your hips. If you can do it at all, significant energy will be wasted on balance and support. Energy that should be used for propulsion. Most people cannot do it at all. Some can but actually move backward.
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