Originally Posted by Pilot
Looks like you have some of the issues I was having a few months ago. Try to keep your shins as perpendicular to the floor as you can.(they will still naturally go forward a bit) Notice how far your knees go forward? I believe that stems from inflexibility in your hamstrings. I've been working on my lower back, calf, and hamstring flexibility and I can pretty much keep my shins close perpendicular now. The movement feels a lot more controlled and solid now.
It's definitely a flexibility issue, and I do want the knees to stay back. It's either hamstrings or hamstrings + hips. It is difficult for me to bring my knees to my chest w/o rounding my back, no matter the angle at my knee. I don't know exactly which muscle is limiting me, but I am constantly working on flexibility at the hips and hamstrings - in short, I agree with you. I am really trying to sit back.
I think that when you switch to low bar from high bar, you need to bend at the hips more to bring the weight over your center. This pushes my knees forward in the low bar version, so even though I am more flexible, the net result is still knees forward.
Happily though, and knocking on wood, I am totally pain free at this point and pushing close to max effort (as you can see by how much I'm struggling).
Manton, if you're reading this, it comes from the principle of sitting back into the squat, which is probably the #1 most important part of the lift, along with keeping your chest up. That's the first thing I would hip myself to if I were you.