Back angle in the squat

Hello,

I would like to ask a question about keeping the same back angle on the squat ascent. I noticed in this video (https://www.youtube.com/watch?v=e30ukNlFTPg) of you guys squatting that there’s a slight change of back angle and a slight movement of knees backwards at the beginning of the ascent (especially as the weights get heavier). I remember some prior instructions were that the back angle and knee placement shouldn’t change until about 2/3 way up.

So should we try to maximize the constant back angle as much as possible or is it OK (or even beneficial) to change the back angle slightly out of the hole?

Thanks.

It’s OK and normal for it to change a bit.