Here Ajahn Sinchai demonstrates neck cracking. You can really see the way he feels each body in front of him, making sure that they are fully warmed up, and relaxed before he does the crack. The receiver has his hands placed under his chest giving him the appearance of a hunch back – I think this gives more ‘space’ to the vertebrae, and allows more relaxation and surrender. The crack can only happen when the receiver is totally relaxed. This is a very very difficult thing to do and should NOT be copied without proper guidance as it could result in all kinds of problems including paralysis.
Ajarn Sinchai trained in Medical Massage 41 years ago and has been practicing ever since. http://www.sinchaimassage.com/