In Chen taiji do not tuck in the bottom., the tail bone does not curl inward like a shrimp. The body stays natural. The spine naturally curves in at the neck and the waist. When practicing the body sits, like on a chair, the bottom sinks and the back relaxes. The spine naturally goes in a little bit and extends, the tailbone sinks and straightens some without turning inward. The hips become loose when the spine is natural and when the tail bone is dropped.

When the hips are loose the body turns well. When the hip frame can turn well the muscles and legs twist and turn with the bone. When the hip frame is not loose the muscles cannot twist and turn.

‘Sun kwa’ describes the looseness of the hip and its loose connection to the body frame. ‘Sun kwa’ is the loose hip, the relaxed hip frame.

In this posture the dantian naturally rolls forward and sinks down. The feet will be grounded like growing roots.