Anoher example of an already explained principle: If we have some support we tend to relax toward it in movement and in static contact. For example lie on your stomach and clasp your hands together. Now lift up from the back and check how free you are. Next place the palms or fists at the small of the back and check how the movement changes. Once you experience a movement you can progress from there and learn more. This of course applies to all things.