"Spinal alignment" refers to the proper positioning and arrangement of the bones in your spine. It means that the spine is straight, with the right curves, and each bone is properly stacked on top of the other. Full definition
I like that they use a spring unit as a foundation since that is key for proper spinal alignment. (mommypotamus.com)
They allow the body to stay in motion (some more than others), and also help the pelvis maintain a proper tilt for good spinal alignment. (wellnessmama.com)
Now you can improve your balance and posture, as well as strengthen your core muscles and improve spinal alignment all while sitting at your computer! (thefashionablehousewife.com)