avoiding that back pain

At the grocery store the other day, I saw this young girl doing some pretty heavy lifting as she stocked the shelves. I wondered how she managed to do it without even wearing any back supports, which are not very bulky these days and fit a variety of body shapes, definitely the petite one included. I've had some minor back pain, mostly sprains actually, on and off, and it's not something that I would want to mess around with, since it always ends up coming back.