This is a topic that interests me very much. To what extent do you use the navel to the spine technique (similar to the old school "stomach vacuum" exercise favored by bodybuilders) while dancing? This requires considerable strength in the transverse abdominus muscle, which can be extremely difficult to exercise. Is this part of your dancing? Do you attempt to maintain this position throughout each dance or do you adjust it as you dance for various effects? Do dancers at the highest level have a tremendous ability to create this deep movement/position at will? Is this one of the challenging aspects of dancing that separates the best dancers from the rest? Why do you use this: To create space for your partner, to reduce the curvature in the lower spine, to prevent sides from dropping, to assist in creating diagonal length in the body?