i have a question. sometimes when i do heavy weights (like 350-400lbs) on back squat, i bend a little out of form. i still get to parallel, and my form on the way down is picture perfect. but sometimes when i come up (usually on the last 2-3 reps) i bend over at the waist a little bit. i keep my back nice and tight even in this position, but i dont know if its too late at that point? also, i try to keep my chest up but i sometimes just cant keep straight up. my legs can always get the bar up, besides the occaisional knee going inwards for a second or two, its never my leg strength thats in question. i think that maybe my back is just too weak?
so am i at particular risk for hurting my back, and in what way? sometimes my back is sore for up to 4 days after squat. is this normal or way too bad? btw i wear a belt.
thanks for helping a relative noob.