One of Tai Chi’s most touted health benefits relates to spinal health. The two pictures here, illustrate the point very well (from Peter Payne’s book ‘Martial Arts – The Spiritual Dimension’). All Tai Chi styles invoke their practitioners to maintain a straight back – “no bumps, no hollows”. Some schools actually try to maintain the back vertically erect as well, although that is not the case in the majority of styles (most Yang lineage, Wu family – to which Practical Tai Chi Chuan is related, even the Chens). In these styles, the back must be straight, but may be inclined – as the picture of Wu jian-chuan here shows.
Maintaining a straight back, with the coccyx tucked under the spine, helps to stretch the spine and avoid all sorts of problems of movement and gravity (which spends its time compressing our vertebrae together – see the downward arrow below). Sciatica is often cited as something that Tai Chi can help prevent and remedy … and this is true, but it’s a balance. 5 minutes of practice here and there will not remedy hours of sitting on uncomfortable chairs in bad posture!