If you’re properly aligned you should be able to draw a straight line, infront of your shoulders, behind your hip, to the front of your knee, to a few inches infront of your ankle. This puts the centre of gravity directly over your base of support which allows you to move efficiently. From the back, 33 vertebrae is stacked in a straight line. From the side the spine has 3 curves. One at the neck, one at the shoulders and one at the small of the back.