When standing in a "set position" or setting up for a squat, why specifically are the toes turned out? Paul Chek had given an actual 30 degree figure. Mike Clark added that as the feet get wider, so does the angle of the hip. Is it somehow related to femur head in the acetabulum? Also, where does this information come from? The toe out information seems to be fairly common, but is there any scientific backup for this?
I believe the point Chek is/was trying to make was that the toes can be turned out up to 30 degrees for reasons of comfort and safety. Many individuals will/do have orthopedic differences due to injury history, common physical stessors and of course genetics. When these restrictions are present, an angling out of the toe/foot can "free up" the ankle and/or hip joints, so to speak. This is not an absolute for all people as some will not need such a drastic angle. The measure of 30 degrees is considered the maximum angle for safety/stability of the kinetic chain during a squat. Consider the following points:
- As the toes are angled out, so too must the tibia and femur externally rotate/abduct so as to maintain proper alignment and OIARs (Optimal Instantaneous Axiis of Rotation) of the ankle, knee and hip. Hand-in-hand with this external rotation/abduction must be a slightly wider foot placement as well. All of this equates to maintenance of joint health/integrity and the avoidance of injury.
- This angling out means that the normally sagittal plane squat is now slightly approaching the frontal plane. Take a look at the simplified diagram below. In figure A, you can see the position of the segments in a purely sagittal plane squat. Particularly notice how much more dorsiflexion is required in this version of the squat.
- Contrast this with figure B, which is albeit an extreme example of the sumo squat position very close to the frontal plane. Notice how much less dorsiflexion is required. This is due to the "shortening" of the lever arm (femur) that occurs when the lower extremity is externally rotated/abducted during the squat pattern. This can be beneficial for those individuals who have some restriction in the hip, knee and of course the ankle such as a lack of adequate dorsiflexion. It may also benefit to those with genetic structural features such as an abnormally long femur comparatively speaking to the trunk and tibia, which make up the other two segments of the squat.
If an individual is still unable to learn/perform a squatting pattern with the toes at a 30 degree angle, than "freeing up" the restriction(s) identified in the assessment should likely be the priority. This may be accomplished via some sort of stretching/flexibility and/or joint mobilization technique or therapy such as neuromuscular therapy, massage therapy or perhaps chiropractic care, etc.
For a great resource on mechanics, I suggest Joint Structure and Function - A Comprehensive Analysis by Norkin and Levangie. It's a tough but great read, and it should provide you with the research and evidence you're seeking.