Calcaneal Eversion: Turning On the Core
Calcaneal Eversion , the heel tipping inward from its original contact point on its outer edge as one’s foot hits the ground in taking a step. This motion when it occurs normally-normal amount of motion at normal controlled speed of movement is key to stimulating tri-planar motion proximally up the chain to “turn on “ the core musculature(the power source of the body). Too little or too much of this motion often shuts down the cores ability to contribute to sports performance.
Let’s look at this motion in each scenerio:
- “Just right”: As the heel hits the ground , when taking a step, the calcaneous strikes on its outer edge...gravity and ground reaction forces cause the heel to tip inward as the body begins to travel over the foot. This inward tipping (eversion) is a frontal plane motion but because of the angle of the subtalar joint axis: this motion is converted in to a transverse plane motion of the lower leg(which translates up the chain to the femur, pelvis and lumbar spine). Therefore causing tri-plane motion at the knee (flexion, abduction/valgus and internal rotation) and tri-plane motion at the hip( flexion, adduction and internal rotation) during walking. The muscles job is to decelerate these motions through controlled eccentric lengthening and then accelerate the limb in the propulsion phase of gait through concentric contraction. It is these tri-plane motions in the kinetic chain that “turn the hip and core muscles on” ...and it all begins with the calcaneous and it’s ability to move through eversion.
- “ Too little”: If the calcaneous is not able to move from an inverted position (at heel strike) to an everted position...then the proper rotation does not occur in the lower leg, nor up the chain and the proximal muscles are not properly lengthened (“turned on”). This is often seen in a runner with a supinated foot and/or in arthritic knee patients with varus thrust at theirknees(often stemming from lack of calcaneous motion).
3. “Too much”: Too much eversion is often seen with the pronated or flat foot. The patient strikes in an already everted position and is at their end range of eversion ...therefore the heel does not travel through motion and neither does the lower leg..the switch never turns on....the core is shut down.
A Clinical application: if you are a clinician that is treating a runner with sciatica, iliotibial band syndrome or peroneal tendonitis....check the calcaneal eversion. Inability to eccentrically load the muscles will often cause muscles to attempt to contract in a shortened position where it/they have less power..often leading to overuse injuries.
Make sure to catch next week’s blog to learn more about how to functionally test calcaneal eversion.
To learn more about functional rehabilitation click here.