It may seem like rule number one for avoiding back pain: Lift with your knees, not your back. But McGill says this maxim has it all wrong. He says the hips, one of the major movers in your core, are more powerful and can bear the brunt of a load better than your knees. Next time you lug something heavy, "bend down, stiffen your back, and pull your hips through," McGill says. "That's how to lift heavy objects to prevent back strain."