I would recommend box jumps.

Proper box jumps. Flat footed jump, land and plant heels, extend hips forward to straighten out, then jump back down, land and plant heels, rinse and repeat.

If you've got back pains, you're doing something wrong or with too much weight.

I guess it's hard to judge the difference between soreness and pain from injury sometimes, but if your back is sore, rest it, and double check your form.