Had a good talk with a client today...
"How much should I open up in the hole? Like should I be getting my groin as open as possible pushing my knees out as much as I can or opening up and letting my knees travel forward a bit?"
Good question for a young squatter. And made me realize, he wasn't quite understanding EXTERNAL ROTATION.
External rotation is the act of creating an anchor with your foot or hand (gripping the ground or floor hard) and then using the hip or shoulder respectively to create torque within the joint.
In the bench, that's like turning your elbows toward your knees.
In the squat, that's like rotating your knee toward your pinky toe (without your foot moving).
Not to be confused with 'knees out' which is an old cue primarily used in geared lifting to stretch or fill the gear. In a raw squat, it's not about getting your knees to travel laterally, outward. It is about getting as much torque in your hips as possible and in a sense, pulling yourself down into the squat as you try to tear the floor apart with your feet.