squatting: form check and lower back soreness?

[brokeman]

I'm doing the beginner stronglifts 5x5 program. I used to get a very sore back immediately after low bar squatting due to butt wink. I've been working on my mobility a lot and foam roll /stretch in between sets which help but still feel tightness in the lower back and feel like I'm not using my glutes at all while squatting. The next day usually my quads and hamstrings are sore and lower back is tighter than usual. I'm afraid of continuing to increase the weight and hurting my lower back. Any tips?

youtu.be/WkXjWYhMwes

[CheekyKuntBrah]

Your lumbar is hyperextended because you’re sitting back instead of sitting straight down into your hips. If you get your pelvis and lumbar in a neutral starting position it’ll take the pressure off your lower back and sit straight down by allowing your knees to travel forward.

Watch content like this https://youtu.be/F-siVhUVReA and especially this https://youtu.be/u91tLOpHIHo

[k11w]

Rack / unrack facing the other direction. (face the rack)

This makes me think of Kelly Starrett's words: "if it feels sketchy, it's sketchy." Be careful. Be uncomfortable but don't be compromised.

Keep working on mobility on your recovery days. Stick with the program. Your body will adapt to the movements and become more integrated to where some parts aren't more sore than other parts.

Don't go as low. If you look at the bottom of your squat, you can see your pelvis turn over in those last couple inches. If you keep working on your mobility in between lifts, you'll be able to get deeper. But don't work on your depth when the bar is on your back.

I'm a big fan of paused (or even double paused) squats / deadlifts to strengthen your core so that you don't hyperextend like cheekykuntbrah said.

Overall though, nice job. Keep it up.