The picture shows an individual standing on a platform made of nails as part of a martial arts demonstration.
Standing on the bed of nails is a Yin building exercise.
The reason why standing on the platform of nails is a Yin building exercise has to do with the weight distribution of the body. An individual with a weak Yin part of the body will tend to settle their weight on a few spots. Putting that amount of pressure on a nail would cause the nail to penetrate their feet.
Distributing the weight of the body is one of the functions of the Yin part of the body. When the martial arts trainee or some other individual stands on the platform of nails, their feet will get poked by the nails wherever they settle their weight on their feet. The pain of the nails poking into their feet will force the trainee or other individual to adjust their weight so they do not get poked.
Avoiding the pain of the nails poking into their feet through the process of adjusting their weight will strengthen the Yin part of their body and teach them to control it.
The strengthening of the Yin part of the body will give the body a “padded” or fattish look to it. That padding provides a more localized absorption of force or pressure in addition to the more large scale absorption of force and pressure attained through adjusting the body weight.
There is not much to show in the way of pictures for this blog entry. Everything that is going on involves the invisible forces of the body balancing themselves and counteracting the invisible forces that are being exerted on the feet by the platform of nails.
An additional comment can be made on how the feet and legs have been changed as a result of the man’s strong Yin development. Both of the man’s lower legs look like they curve into the feet,
and both feet are splayed outwards.
Both of those changes are common characteristics of strong Yin development of the body.
Walk in a slackline does not exercise the ying part of the body