Originally Posted by
Treg
Before I discovered Starting Strength, I learned to high bar back squat from a bunch of know-nothings online. So when I read the book and switched to low bar squats, I struggled with this issue for a while. I think what finally got me past it was doing long paused reps at very low weight, to allow myself to check and correct my form at the bottom, then concentrate on keeping the hips and knees back while hip driving up.
Dillon Spencer provided some links to some very usual videos. Take a look at those and watch the people who lean into the squat really well. Get that image firmly planted in your head of what it looks like when someone leans forward properly as they descend. Really sit and study that, over and over.
Then go to the gym. Get under the bar - UNLOADED. Get tight and slowly descend. Concentrate hard on shoving your knees out, and LEAN IN, just like you saw the people in the videos doing it. When you reach the bottom of the range of motion (which is really determined by when you can no longer stick your butt out any farther BACK, not down), hold that position and concentrate on what if feels like to REMAIN leaning forward with your hips BACK and your knees staying where they are, not leaking forward. Then drive up with your hips while stilll leaning forward and don't let your knees slide forward.
Again, sorry to shout, but DO THIS WITH THE UNLOADED BAR a whole bunch of times. Like, way more than you want to. Then maybe go up to 95 lbs. and do the same exercise, and so on. You will not be able to fix this problem if you insist on trying to work on it with anything but very light weight on the bar at first, until you're really getting the feel.
Hope this is helpful.