I lived to squat, now I have 8 herniated discs and I know it's because of the weight that I used to put on my shoulders was extreme. But that's what everyone did in the day. Then we learned about lunges and my God did they save me. To this day I'll use a leg press machine, a squat machine but the walking lunges, smith lunges and just doing lunges onto a aerobic step is my favorite to maintain my legs and never tweak my back and if I wanted nice deep cuts in my legs for a show I would do more lunges. I can tell you from experience ( a full avulsion ) that if you'd Ever do heavy lunges make sure you have a good spotter and also that you keep your legs in a straight path and never step to far out or you will have a avulsion and end up in the hospital getting it re-attached.