Chaotic,
I was going to ask if medication would help. Is there any way you can ask how much you are going to have to be massaged (sorry I couldn't think of any other way to phrase that)? Could you tell your supervisor that you want to do this but that at this time you need to forego that experience? You can say you have a back injury or whatever if you want.

I had a massage and it made me sore for a week. I have vowed never to have one again. I'm interested in what they call craniosacral massage. Does that really help bring up memories? My massage didn't bring up any memories or thoughts, just massive muscular pain.

I hope all goes well!