OK here's what I see:
1. you engage the lift from the knee (on the way down) - you are low bar back squatting but letting the weight drive you down by pushing the knee forward rather then engaging by pushing your butt back!
2. your stance is too narrow - its hard to tell from the angle but I can almost guarantee that if you widen your stance by 2 inches and angle your toes out a bit more then you'd like too it will allow your pelvis track more efficiently.
3. You need to allow the hamstrings to engage - I'm betting you feel the vast majority of muscular tension in the quads when lifting. If you're front squatting or Olympic Back Squatting fine, that would be the point but you aren't you need to get stronger first.
4. The posterior tilt at the bottom of the movement will almost assuredly be solved by pushing your butt back some and letting yourself lean forward more. (folding at the hip) This is a posterior chain exercise and your doing it with your quads. This is also causing you to shift the weight onto the toes.
5. From the bottom you need to drive the hips up! - When you are in the hole you need to think of pushing up against your sacrum... Think of reaching for and sliding your ass up the wall behind you. This should be a life changing experience for you because you wont even notice the weight on your back at this point until it gets REALLY heavy. This is driven from the hammies...
6. lastly you need to DRIVE your knees out (apart) as you drive your hips up - this will engage the adducters, small muscles yes but important in the proper lifting of really heavy things!
Here are my cues for you -
Initiating the movement:
Plant your heels
Push your butt to the wall behind you
Lean forward - TIGHT BACK TIGHT BACK
Getting out of the whole:
Slide your butt up the wall behind you!
Hips UP! Knees out! TIGHT BACK TIGHT BACK
Hips forward (to lock out)
Thats it! I mentioned that this would help correct the posterior tilt, let me explain why I think this. Because I see it all the time! Your posterior tilt comes from a strength imbalance between your front and your back, NOT A FLEXIBILITY ISSUE perse. The flexibility is there, your spinal errectors are not strong enough to keep your sacrum supported in place. Your hamstrings aren't even doing anything at this point. Your glutes are tight and the psoas is getting lazy. This is causing your pelvis to roll under (posterior tilt). You need to do something that will get all of the muscles doing what they are designed to do.
The torso muscles basically have one primary job - keeping your spine intact. Or as we CrossFitters like to say midline stability. (the swing arm of your crane) Get them strong doing this properly and it wont be an issue anymore. My posterior tilt vanished almost immediately after spending some time with Rip. I in turn have been teaching these things to others in far worse condition then you and they are doing just fine...
just for reference I weigh 150
(I'm not trying to show off I have far to go myself)
FS - no idea
I was where you are about 2 years ago. And only marginally better about 8 months ago since then my numbers have all jumped drastically! Technique is everything...
Do that and you will be good to go! No ifs ands or buts about it you'll do well!
NOTICE: Pierre Auge's opinions are subject to change at any time and without prior notice.
To give real service you must add something which cannot be bought or measured with money, and that is sincerity and integrity. - Douglas Adams