Why do we crouch down to lift a heavy box?

The body’s centre of gravity normally lies near the belly button. When we bend forward and lift a heavy box, the centre of gravity of the ‘body plus the box’ lies far away from our body. This puts a lot of pressure on the backbone, and the back muscles resist this. In contrast, when we crouch down and get up with the box, the centre of gravity remains near the body. This puts less pressure on the backbone and helps keep our backs healthy.