First deadlifts and squats after back injury

[Brandon Hill]

I'm using Starting Strength to rehabilitate my back. (I was hospitalized due to low back injury.)

Below are my deadlift and squat videos as I begin my journey.

I would appreciate any corrections/suggestions that I can implement before I try moving up in weight so I don't end up in the hospital again.

Deadlift
Deadlift 2024.08.31 - Google Drive

Squat
My ankle dorsiflexion does not permit me to deep squat. I'm hoping that continuing to squat will increase my flexibility and allow me to get lower and lower over time.
Squat 2024.08.31 - Google Drive

Thanks in advance!

[Mark Rippetoe]

What exactly was the injury? Have either of you read the book?

[Martin Shenfield]

You need to sort your squat out. I don't really believe your ankle mobility issues. Can you sit in a chair? Most of them would be lower than what you're doing. My old mum can squat lower than that.

Also, wear a belt. You've been hospitalized for a low back injury. I put belts on from warmup 1 on deads and about halfway through for squats.

[Maybach]

Your ankles do not need to dorsiflex any further to reach sufficient squat depth.

[Brandon Hill]

L5S1 disc herniation

Yes

[Brandon Hill]

If that's the case, why does my COG shift posteriorly when I squat deeper, even while keeping the back angle correct?

[Brandon Hill]

I envy your mum. Sitting in a chair is difficult. I literally fall into a chair to sit because of this issue.

[Satch12879]

Because you’re likely not keeping your back angle correct.

As for your video, where are your knees going?

[Maybach]

If that's the case, why does my COG shift posteriorly when I squat deeper, even while keeping the back angle correct?

As Satch alluded, because a) your back angle is not correct. It is not established early, changes throughout the first part of the lift, and does not become sufficiently horizontal, and b) your knees are not driven out, which means your hip angle cannot close further, which means the only way you can squat deeper is by closing your knee angle, which means your COM shifts posteriorly as the knees lengthen the moment arm between the COM and the midfoot.

The maximum dorsiflexion required to squat deep is that sufficient to bring the knees over the toes, which you are demonstrating the ability to do here. Shove your knees out and BEND OVER. These are classic bits of SS advice.