Back pain after squatting

[Mr.City]

Hey guys,

I've been noticing that my back feesl stiff either right after or a few hours after my squat session. I focus on keeping a tight back during the squat. I have a recent video of my squatting 320 and don't see any slack in my form that would cause this.

http://www.youtube.com/watch?v=3oEgf6M1_yQ

Is this common when the weight gets heavy or is my form off? Thanks in advance.

[Locutus]

Your back looks loose at the top of the movement. You then seem to achieve much better extension on the way down.

Also, (at least based on the second video), you knees seem to come in quite a bit on the ascent.

[Mr.City]

I never noticed my knees. You know, it never occurred to me to shove my knees out during the entire movement, I only thought to do it during the ascent. Also, are you saying I tighten up, back-wise, on the way down?

[Locutus]

I never noticed my knees. You know, it never occurred to me to shove my knees out during the entire movement, I only thought to do it during the ascent.

You mean descent? But yeah, you want to keep knees out the entire movement.

Also, are you saying I tighten up, back-wise, on the way down?

Yes. But, you want to get tight before you initiate any movement, and preferably before you even unrack the bar. I'm not sure what the exact cue for you will be, but experiment with scapula retraction, "chest up", and/or grip width.

If you don't see what I mean, try focusing on the chest area. You can see it round whenever you lock out.

(Also, probably unrelated: where is your belly button in relation to your belt?)

[Mr.City]

It's over the bellybutton area.