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How do the foot and ankle muscles affect the most common musculoskeletal deviations in the human body?

This is an excerpt from BioMechanics Method for Corrective Exercise-2nd Edition, The by Justin Price.

The muscles just described play a vital role in mitigating the two most common deviations of the foot and ankle. They provide strength and support to absorb shock and transfer the body’s mass forward, side to side, and in rotation during weight-bearing activities. They also store potential energy to help with propulsion and to create powerful athletic movements. However, when musculoskeletal deviations affect the feet and ankles, they cannot perform these crucial tasks correctly. The foot and ankle structures can become strained and stressed, and musculoskeletal compensation patterns elsewhere in the body can become exacerbated, making everyday activities and exercise problematic and painful.

To illustrate how the foot and ankle muscles help prevent overpronation and lack of dorsiflexion, consider what happens when a person is walking. During a normal gait cycle, the feet and ankles work together to help stabilize the body’s center of gravity and displace the weight of the body as it travels over the foot (Chinn and Hertel 2010). This helps to maintain an upright position and forward momentum. When a person begins walking, the outside of the heel connects with the ground first. At this point in the gait cycle, the ankle is inverted, and weight is on the outside of the foot and heel. As weight is transferred forward into the foot and it makes full contact with the ground, the ankle rolls inward (everts) and bends forward (dorsiflexes) to transfer weight over the entire foot (Donatelli and Wooden 2010).

These movements are critical to helping ensure that the foot and ankle muscles act like bungee cords to decelerate stresses. As the foot and ankle pronate, the muscles that support the arches of the foot lengthen under tension as the insertion points of these muscles (under the foot) move away from their points of origin (on the lower leg). This creates potential energy, which is then used to help roll the foot and ankle back out and to push the foot down and off the ground to complete the gait cycle. This motion becomes problematic when the foot and ankle overpronate. When the muscles that limit pronation do not work correctly or lengthen effectively, the bungee cord effect is lost. Consequently, very little tension is created in the muscles to prevent the foot and ankle from overpronating. This results in the ankle failing to bend forward (dorsiflexing) enough to transfer weight correctly over the foot (Donatelli and Wooden 2010).

Here are two examples of how the bungee cord action of specific muscles controls both overpronation and dorsiflexion.

Example One: Tibialis Anterior and Tibialis Posterior

As the foot pronates, the medial longitudinal arch flattens out slightly, and the toes move forward and away from the heel. This causes the insertion point of the tibialis anterior (in the midfoot area just behind the toes) to pull away from its origin point on the front of the tibia. This pulling motion creates tension and activates the bungee cord effect that helps to support the medial longitudinal arch and decelerate the foot, ankle, and lower leg as they roll inward. The tibialis posterior, which runs from beneath the foot up and across the back of the leg to its origin high on the back of the tibia, also lengthens as the foot pronates. Its bungee cord effect prevents the lower leg from internally rotating too quickly over the foot. The actions of these two muscles help coordinate the timing of the lower leg’s internal rotation and ensure the foot pronates at the appropriate rate. Since the movement of the lower leg also affects the position and timing of the knee as it moves medially, these muscles also indirectly affect knee position and function.

Example Two: Soleus and Gastrocnemius

After the heel has made contact with the ground during the gait cycle, weight is transferred forward as the lower leg and knee move over the foot. The soleus originates high on the back of the lower leg and is attached to the back of the heel by the Achilles tendon. As the knee and ankle bend, the movement of its insertion point away from its origin point enables the bungee cord feature to help control both dorsiflexion and knee flexion. As the gait cycle continues, the foot remains in contact with the ground as the leg extends behind the body. During this movement, the gastrocnemius lengthens like a bungee cord, and the tension in the muscle slows down the lower leg as it continues to move forward over the foot and the knee as it straightens.

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Go to the online video to watch video 8.3, where Justin talks about how dysfunction of the calf muscles can affect the most common imbalances.

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If the calf muscles and other muscles of the foot and ankle (such as the anterior and posterior tibialis discussed in example one) do not prevent the foot from overpronating, then the foot and ankle collapse, and the lower leg rotates inward too quickly instead of coming forward over the foot as it should. This disruption of the forward motion of the lower leg over the foot is why overpronation and a lack of dorsiflexion are inherently linked. Moreover, when any of the other muscles of the feet and ankles discussed in this chapter are not working correctly, overpronation and lack of dorsiflexion can result. This can lead to the structures of the foot and ankle becoming stressed, compensation patterns developing elsewhere in the body, and—over time—pain or injury.

More Excerpts From BioMechanics Method for Corrective Exercise-2nd Edition, The

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