When you look at the spine from the front or the back, all 33 vertebrae should appear stacked in a straight line. From the side, the spine should have three curves:one at your neck, one at your shoulders, and one at the small of your back. You aren’t born with this s-shaped spine. Babies’ spines just have one curve like a “c.” The other curves usually develop by 12-18 months as the muscles strengthen. These curves help us stay upright and absorb some of the stress from activities like walking and jumping.
If they are aligned properly, when you’re standing up, you should be able to draw a straight line from a point just in front of your shoulders, to behind your hip,to the front of your knee, to a few inches in front of your ankle. This keeps your center of gravity directly over your base of support, which allows you to move efficiently with the least amount of fatigue and muscle strain.