Spine

In utero the spine is a smooth kyphotic (forward) curve from the bottom of the coccyx to the top of the neck. After birth secondary or lordotic (backward) curves begin to develop in the spine as the baby struggles to involve itself with its environment, first by pulling the head back (cervical curve), and then by sitting and then standing (lumbar curve). The various curves in the spine are fully developed by the age of ten. They are:

cervical – lordosis
thoracic – kyphosis
lumbar – lordosis
sacral – kyphosis

They give the human spine its characteristic double-S shape.

The force (tropism) that causes the spine to develop in this way is the sense of curiosity in the infant. Curiosity makes the infant extend into its environment; it doesn't just arch its head back it extends it up and away to better see and better connect, and as it extends its head up and forward the sacrum and coccyx naturally extend down and back: when a healthy spine extends it does so in both directions. An unhealthy spine is basically one that has either stopped extending altogether or one that extends unequally. An unhealthy spine belongs to an unhealthy person – it is indicative of an unhealthy engagement (or lack of) with the real world. In Tai Chi we must be vigilant that our straight spine is straight because it is extending with curiosity (with spirit) rather than because we are stiffening it or forcing it out of its beautiful natural curvature.