To the other excellent resources already posted, I'd add Jerzy Gregorek's site The Happy Body. He was referenced in Stu McGill's book Ultimate Back Fitness and Performance. Gregorek is an Olympic lifter, gold medalist, blew a disc in his back in his 20's, now is an unwavering advocate of building the right combination of flexibility, strength and power to optimize performance while reducing injury risk. Check out the Candle Squat and other flexibility tests here. Personally, I wouldn't put weight on the bar until you are proficient with Candle Squat. These techniques will help you find your functional squat range and make sure you don't exceed that range and move into injury zone.

Dr. Phillip Snell
www.FixYourOwnBack.com