Mulabhandha; Ramaswami's fishing rod analogy

One of my favourite sections from Ramaswami's Sept Newsletter 2011 (in full here )

'The spinal column descends from the occipital region and we have the aajna chakra in that region and the sahasrara is in the cranial region. The tailbone is the baby of the assembly at the bottom and tucked nicely but is surrounded by heavy muscles and tissues and protected well. It has some mobility.

Since it is the root of the spine it is also known among Yogis as the Mula. Since both Hata Yoga and Kundalini Yoga are predominantly connected with the spine the mula becomes an important aspect of yoga. When one wants to work with the spine, it, the coccyx, should be firmly anchored. Let us consider the example of the fishing rod (old times). It has a flexible pole, a string and the bait. (sorry I could not think of an ahimsa example). One holds the pole at the far end and when the bait is taken, the pole bends. The fisherman will have to hold the pole firmly so that the pole can bend to the extent required, even though there will be some play or movement in the hand of the holder. Further he has to hold at the farthest point, holding a bit inside the pole reduces the leverage and the pole will not bend sufficiently.

The coccyx and sacrum (sacro-coccygeal section) are at the bottom of the backbone. The coccyx is at the very end of the spine. It represents a vestigial tail (hence the common term tailbone) and consists of three to five very small bones fused together. There is, limited movement between these bones permitted by fibrous joints and ligaments. The sacrum is a large triangular bone at the base of the spine and at the upper and back part of the pelvic cavity and where it is 'inserted' like a bone wedged between the two hip bones. Its upper part  is connected to the last lumbar vertebra and the bottom part to the coccyx. In children it consists normally of five unfused vertebrae which begin fusing around 16 years and become completely fused around 26. It is kyphotic (curved, concavity facing forward). Even so, it is
now an established fact that the sacrum moves between the ilia by both ambulatory and respiratory motions . It would therefore point to the logic of the use of fuller breathing in vinyasa movements as in Vinyasa Krama.

So the mula or the tail bone will have to be held firmly during the spinal exercises. And the yogis used the well known technique called mulabandha which is contracting a few groups of muscles surrounding the tailbone:  the perineum, rectum and the gluteal muscles. All spinal movements, the forward bend,the rounded back, the turn, the back bend, the side bend, all will be better if the mula is gripped firmly and engaged.'