Mechanical activation of vagal nerve fibers through neck stretching activates sensory and motor fibers, with the majority of the parasympathetic effect occurring on the right-hand side.

“this basically mechanical activation of this vagus nerve pathway, it doesn't just feel good because you're stretching your neck out. It does indeed activate some of the sensory, and probably some of the motor fibers as well, that course through the vagus nerve. And keep in mind, this is interesting, that the majority of the parasympathetic effect of mechanically activating those vagal nerve fibers, is going to be on the right-hand side.”