Everybody’s body is a different, so Pilates terminology will effect individuals in a different way. On the left is a picture of my spine in imprint (my low back pressed against the floor). This is the positions we typically use if we are going to lift our feet off the ground. It helps protect the back. On the right is a picture of my spine in neutral (there is a slight arch in my low back like the natural curve of a spine). We use this position when we are doing exercises with our feet on the floor. It helps incorporate additional abdominal muscles, so that you can get more work with each exercise. Range of motion for everyone differs. Most people also feel more comfortable in one position over the other.
Lie down and do some pelvic tilts–rock from neutral to imprint 10 times and see where your spine prefers to be. It will help loosen our back.