There’s a lot of debate about “tucking the tailbone” in Tai Chi. Some people are big exponents of ‘tucking’ or centring the pelvis, which removes the curve of the lumbar spine. Other people prefer a more ‘natural’ lower back which has more of an inward arc.
For me, it’s not that either of these positions are wrong in Tai Chi, it’s that the idea of holding your spine in a fixed position that is wrong.
If I see anybody practising Tai Chi with a fixed, ‘held’, lower back shape I think it’s just time to sigh and move on.
The lower back is part of the dantien area. This area must be relaxed and free to move.
By far the most common way people hold the spine in this position with tension is with an inward curve. If you see a curved-in back then this area is not relaxed. It might be more aesthetically pleasing but there is no way to connect the power of the ground and legs through the dantien area like this – it’s essentially cut off from that power.
Sure, you can generate power in other ways, but unless you relax the lower back power can’t be transferred from the ground.
Xing Yi is the oldest of the ‘internal’ martial arts. If you look at videos of a precursor art to Xing Yi, called Dai family Xin Yi Lie He, you can see their art has an exercise called squatting monkey as its foundation practice. Look at how it bows and unbows the spine. There’s a lot of flexibility being trained here.
These exercises are like basic, large frame, training exercises for conditioning the muscles and tendons of that area, and the movement can become a lot smaller in usage.
If you’re a Tai Chi practitioner you don’t need to start doing Squatting Monkey practice. I’m not saying that, but you do need to start paying attention to your lower back as you do whatever exercises you are doing – form, Pa Tuan Chin, Silk Reeling, Chi Kung, etc…
Ask yourself what your lower back is doing. Am I holding tension in it? (Here’s a big clue – you are!) and how should I release it? How about when walking around town, or pushing a trolley in Sainsbury’s? You’ll be surprised by how often we hold tension in this area.
Next think about the role of breathing and how it relates to the lower back. If we are doing deep diaphragmatic breathing (which makes the abdomen swell) then it should also be expanding at the back of the abdomen too. Ask yourself, do you have any flexibility here when you breathe in?
If not, then you know what to do.