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Biomechanics - Gait Cycle
YOUR GAIT CYCLE
Your gait cycle although is as individual as you are, it still must maintain some specific biomechanical patterns to allow the body to use less energy, create less stress on the joints and supporting tissue to allow you to compete at the level you wish without creating injuries.
The gait cycle or stride as it is called has two primary phases called the Stance phase (weight-bearing phase, closed kinetic chain phase) and the Swing phase (non-weight bearing phase, open kinetic chain phase). Each of these two phases has 3 sub-phases with in them. The sub-phases within the stance phase are heel strike, midstance, and toe off. The swing phases sub-phases consist of follow through, acceleration and foot descend. For our discussion we will use the right foot for our example while describing the three phases. Although each phase is very important the weight bearing or stance phase will receive most of our attention.
SWING PHASE
The three phases of the swing phase are follow through where the foot coming off the ground takes the leg back behind us. As momentum shifts and we begin bringing the leg forward this is called acceleration. As the leg comes forward and begins coming down toward the ground this is called foot descend.
Our concerns during swing phase are making sure the leg comes straight up behind us and does not turn inward or outward with the foot or does not flare across or away from our midline. As the foot starts to descend to the ground for heel strike it must stay in the same plane and not swing out or cross over the midline of our body.
These types of alterations will place additional stresses on the muscles and joints leading to repetitive microtraumas, which will ultimately cause injuries.
STANCE PHASE
Heel Strike
Begins with the right foot making contact with the ground on the posterior lateral aspect of the calcaneous (heel bone). During this time the foot is slightly supinated or inverted (turned inward) this allows the foot and ankle to better absorb the forces that are placed on the body when the foot strikes the ground with each step.
Midstance
As momentum goes forward the weight bearing forces pass along the lateral (outside) border of the foot to the metatarsal bones (toes). During this time the weight bearing begins spreading in the direction of the big toe as the foot begins rolling inward (pronation).
Toe Off
As the forces are spread towards the big toe from the inward rolling (pronation) of the foot, the weight bearing is now shifted to the medial cuneiform and base of first metatarsal (big toe). This affect causes the muscles of the lower leg and big toes to contract raising the heel off the ground and flexing the toes.
As this dynamic movement takes place at the foot the stresses placed on the muscles and joints above the foot are registered at accumulations of 10 times our body weight. If someone is referred as a hyperpronator (flat feet/foot rolls inward excessively) it will now cause not just additional stresses on the foot joints, plantar fasica, and musculature of the foot; but will now cause the lower leg (tibia) to slightly rotate medial, which now stresses the knee which stresses the hip joint which stress the low back and continues as a chain of stresses up the spine to the base of the skull. Just think how many times this occurs with each side of your body as you are running and walking.
As mentioned above its these stress that take place not just in the runner and walker but anyone who does repetitive activities and their feet, legs, hips, spine and musculature is not working together in harmony or homeostasis.
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