I have read plenty on squat form and such. I followed most of it but there was one thing I didn't take too seriously. That is, I never had pain when doing squats with my back a bit over arched. I never have had or seen someone complain about pain from it, I just heard it's unlikely for a guy to be able to do it, and that it is bad. I made my hips more flexible than the average dude so I was/am capable of over (hyper) extending my back.
From using my over extended squat technique, I got a better stretch reflex, no back rounding and it was just plain out easier to do. So I thought I was all good.
I was wrong.
I went ice skating the day before my Monday workout, fell down and landed on my hips a few times, but that didn't cause any pain for more than 5 seconds. On Monday, I squatted with my not-super-grand form. I squatted 270pounds for 5 reps for 3 sets. Difficult load. No pain after my workout, feeling dandy with a new personal record under my belt... but later that day after sitting for awhile, I noticed pain in my right hip. It always clicked in the past, but never hurt. Just walking hurt a bit. After walking around a bit the pain dissipated. I tried a few squats to see how they felt. Bam! Pain. This pain didn't feel muscular, it felt like joint pain, almost like bone pain.
From that day, I've been resting my hip... which I hate, being a sprinter who likes squatting and dead lifting. I'm not sure if my pain is coming my skating fails, or from my squat form. I'm leaning on my bad squat form though, because when I tuck my hips in (contracting abs and glutes) and do a test squat the pain nearly non-existent (tucking the hips is proper form), but might ache while I walk away from my squat test.
Now that I knew mostly what caused the pain, I looked into what it might be. From what I read (never fully trust online sources when self-treating), I might have some hip impingement... which I really hope I am wrong, because hip impingement would really stink.
I watched some really neat videos by this CrossFit guy. If you want to look into his stuff, look up mobilitywod. What I got from him is that the hyper extending of the lower back rotates the pelvis back (no duh), thus, limiting the ball in socket joint of the hip (holy flying cows, why didn't I think about that before?). That limitation isn't good, because I could be pinching my femur and my pelvis together because of that limitation, causing impingement.
All in all, my advice to you is: never settle for iffy form just because it feels easier and causes no pain...for now. It might in the long run!
This means for your squats, don't hyper extend your back... yeah, like ever...but don't use this as an excuse to round your back, that's still pretty darn bad for you. Keep a straight back!
Edit: today, after some pain was dissipated, I noticed more of the pain is right above my hip in the lower back... maybe this is just a minor back injury telling me to fix my form in some exercises...
