The traditional ‘yoga’ handstand is quite different from the ‘acrobatic’ or ‘circus’ handstand (if you know what to look for).
While it depends on what style of yoga, overall, yogis tend to be more used to dragging the scapula down, keeping the chest open and the shoulders back. This can be helpful for standing posture but it’s a less optimal position for handstands.
This taking of the scapula down often leads to what in acrobatic terms would be called ‘closed shoulders’. This shape lends itself to a body alignment where the chest is out, the back is slightly arched and the feet or butt end up drifting over the shoulders and wrists to compensate. If done regularly without understanding how to properly activate, utilise and strengthen the serratus anterior muscle, the rotator cuff muscles are likely to suffer.
The photograph in BKS Iyengar’s Light on Yoga of him in Adho Mukha Vrksasana (translated as ‘downward facing tree pose’) is the shape of an almost perfectly shaped letter J, with his legs pointing straight up to the sky and his chest curving towards the ground.
This J shape is working with the natural curve, it’s working with the body. It is a beautiful shape found in nature — if you ever see a chimpanzee handstand, and you should (it’s adorable), you will see the naturally curved ‘banana back’.
A completely straight ‘acrobatic’ line is not something we expect to see in nature, it is something we see in circus — an art form where artists have worked rigorously to mould their bodies for most optimal performance and aesthetic beauty. So, while yoga follows the natural lines, the acrobatic form works against the natural curve of the body to create a strong and solid shape that is a better foundation for more advanced positions.
Also, in acrobatics, physics won out.
Adho Mukha Vrksasana, the yoga handstand, has evolved with a different purpose in mind from the circus equivalent and as a consequence, the shape is different, just as the circus handstand shape is slightly different to the gymnastic version. These similar shapes are clustered under the umbrella of ‘handstand’ but all have slight differences from one another.
Yoga loves playing with the idea of perception, yogis daily navigating their way through a mindful practice trying to become increasingly conscious of the ‘narrow chinks’ through which we view things. None of these poses are more or less ‘correct’ than any of the others — the confusion happens when we ask one pose to do the job of another. For example, if a yogi spends as much time upside down as say a hand balancer without the proper preparation or technique, the pressure on certain parts of the body can become too much and cause injury.
The circus handstand, in its current aligned form, has been developed to avoid injury, increase technical ability and enhance aesthetic beauty. The Chinese circus found that they could contort in their handstands, making art that way, but it was the Russians who analyzed the physics of it and worked out that the perfect line was optimal, which gave hand balance a big leap forward in its evolution.
Thus, science and aesthetics have combined to create the ‘handstand stack’ in which a straight-line is formed.