Help me identify what was this/hows this particular effect achieved

[Unregistered]

So the other day I was just talking to my friend about random thing, when the conversation made a right and he started talking about shoulder massages, and just said I bet you never had one like this. And he just put his hands on my shoulders and squeezed really hard, did someking of motion, and chills ran through my spine, I could feel of my hairs standing up, it was a weird but rather pleasant sensation. I've googled this but I couldnt really find what was the he trigered/did to achieve this with 100% guarantee of success. Needless to say Im imbarassed to ask him this.