Lifting your hips while benching?!

It will hurt your back and provided you can lift at least 6 reps, it's fine to be lifting that weight for strength. The simple solution is to use a weight belt to strap yourself tight to the bench. I have seen guys put two 45 pound weights on top of their hips (ouch!) and even have a buddy sit on them (very effective, but it looks odd). You should also try digging your shoulders into the bench and focus on pressing from your chest through your upper back.

I dont think you will injure your back. Im in a weight lifting class at school, and I do it when Im struggling and it really helps. Try bending your knees and tucking your feet onto the bench (if you're not that tall, and the bench is long) and this will help :)

just dont lift sooooo heavy you need to do that. it wont injure you but it makes the lift not mean as much and not work the muscle right