Backbending is supposed to contract the muscles along the spine and the muscles of the front of the body should shorten to facilitate the extension of the back. Most people that I watch unconsciously lift their chest up off the floor compressing the lower back muscles and vertebra.
There is a difference between contracting and crunching.
Unfortunately it is easier to do the pose badly even though you are not accomplishing much. Stepping back to do it correctly will make the pose harder but your lower back happier. I refer to this pose as Winged Victory.
- Lie on your stomach. Interlace your fingers behind your back. Lengthen the back of your neck looking straight down.
- Draw the belly in lift your trunk up off the floor in one piece, lifting the rib cage up evenly.
- Keep your chin soft. The head, neck, and chest want to move together.
What does your back do in backbends? The muscles of the back body should work together with the muscles of the front body to find extension.