An overextended lumbar extension?

[SmokingSnake]

Hi Coach,
My title pretty much sums it up, I am posting 2 of my latest squat videso(2nd one deeper then the first).
On my last workouts I focus on sticking the ass out and moving the hips, I find it harder to reach good depth and sometimes I also lose my back angle, pressure on the lower back is bigger too.

Is there actually such a thing as an overextended lumbar extension?

Should I be lifting the chest higher in these videos and that might allow to reach better depth and bounce?(i'm shoving the knees out all the way up and down)

1st set
http://www.youtube.com/watch?v=0rtyU...layer_embedded

2nd set
http://www.youtube.com/watch?v=LzItp...layer_embedded

[Mark Rippetoe]

There is definitely such a thing as overextended lumbar. You don't have it.