If your squat looks like you're hunched forward, and your back has rounded out, you have a posterior tilt. There's room for a small movement in your squat where the lumbar portion of your spine rounds out (also known as a butt-wink (lol, butt-wink, I know right?!)). But, if it's excessive (like the picture attached to this blog), then we need to fix that before you do yourself some damage. It also doesn't lend itself to a strong position to squat heavy with.
Parallel lines
Take the bottom of your ribcage and draw an imaginary line. Do the same at the top of your hip. During a squat, we want to keep these lines parallel. This ensures the torso keeps as it should, acting as a column of strength, with as even as possible force going through the spine.
Scissored lines
If you have a posterior tilt, these lines will cross at the front. This puts the spine in a compromised position. We don't want that, especially in a squat. The extra load on the back going through an excessively flexed spine can put you at risk of injury. Not only that, but there is what can be referred to as an 'energy leak' through the back, as seen in the picture of me squatting.
This energy leak means we aren't transferring force efficiently. This means we won't be able to squat as much as we potentially could, until we position our hips better.
45 degree plate squat
This is an excellent movement to help you drill home keeping a tight back. Watch my YouTube video to learn how to do it. Add it in to your warm ups before you squat, and it will teach you to pattern correctly your squat, and should keep those lines parallel.
Give this a go and see if your squat improves.
Thanks for reading!
BennyFit