I have a very pronated left foot. Through other courses I learned that pronation causes my tibia and femur to internally rotate. As a result, should strengthen my external rotators? How does this tie in with AF ER on the left?
A pronated resting left calcaneus (compared to the right) is very common in the presence of the Left AIC. The frontal plane shift toward the right across the pelvis tends to invert the right foot and evert the left foot as the center of gravity is directed laterally over the lateral border of the right calcaneus and foot. So it turns out, your very pronated left foot needs a global pelvis repositioning into left AF IR and left adduction to minimize the excessively everted nature of the left calcaneus (and then stability or motion control shoes to hold it there). Coming out of this eversion (pronated) state then involves training tibial ER and femoral IR. This is the opposite of the original problem of left hip ER, tibial IR and subtalar pronation. So in answer to your question, do I strengthen my left hip ERs? The answer is no. You’ve got to be careful strengthening hip rotators (FA) until you have strengthened the AF acetabular “hole control” muscles to hold things in the correct position. If you don’t properly train the muscles that hold you into left AF IR, then you will turn the pelvis back into the Left AIC pattern. This will give you more left foot/ankle pronation because the center of gravity shifts laterally to the right away from the left subtalar joint.