important to those doing hack squats-

make sure your tail bone and back is flush agianst the back pad. If it starts to float up, your not only cheating you are running the risk of herniated disc or possibly injuring your sciatic nerve, the largest nerve in the human body.

Of course hacks are not the only way to injury your nerves, but some of the most common.

I am and have been dealing with this for several weeks now. I injured my lower back during the summer time and was out of the gym for 6 weeks. I slowly got back into working out while I was in Vegas in September. The heat really helped. Some excercises that helped to relieve the pain; Military press, db raises.Once I am warmed up, I can squat or leg press with no issues. But sitting for a few minutes and then trying to get up, a kick in the nuts would be more pleasant. Coughing or sneezing just adds to the pain and now that its cold out, this just blows!

So do your stretches, warms ups and keep to your form.