Just the mild constant vibrations might have made his neck muscle work harder than usual too.

Doe the chiro you go to have IF stim and or Low level laser? they are really nice for soft tissue , and the laser was great for my wrist , shoulder, foot, elbow specific pain areas.. 20 sec tx and pain was gone..

If he or you have ongoing pain in soft tissue yo might consider an IF stim (like a TENS only better - IMO) of your own , I got mine from Amazon for under 80.00 - had it about 5 yrs now - digital is nicer than analog dials..analog dials are often touchy and you get zapped.

This is the one I have. battery & plug in & very easy to use. but there are many other brands too.
http://www.amazon.com/Roscoe-Medical...interferential