Quote:
Originally Posted by Aidan
You're setting your back by going into hyperextension in the lumbar region, which causes it to unlock as you get to the bottom of the squat. Its much better to set it by using your ab muscles to pull your sternum to your pelvis and then pushing your abs out 360 degrees. This should help your tendency to lose your chest forward a bit at the bottom (it will just already be at that slightly forward angle all the way through the rep).
I'd also think about bringing your stance in a hair. Maybe.
Tuck your chin (ie stop watching yourself in the mirror!).
Bolded is essential to lifting in general. Think of pushing out to the belt. Speaking of that belt, I question the need at this point. Most people put on a belt thinking that it will keep them from having back issues and do not properly use them nor properly strengthen the ab muscles to stabilize your body.
I have not seen your log (if you have one), but it appears you are doing a "Rip style" LBBS (drive the hips up out of the hole). While this is a good style of squat, you want to keep your back angle the same coming out of the hole. Making that angle more acute coming out of the hole will pose problems when you get more towards your max weight, which will turn a squat into a squat-morning. Hopefully Aidan's tip will help solve that issue for you.
It is tough to tell from the back, but it seems like these might be a bit high. If at all possible try and video some from the side, knee to hip height for the camera.