I've included this one because of the massive FAIL all back massages have been on me. It probably doesn't work too well when the only massage-able meat is the square inch between my shoulder blades and my neck or the five inches below my rib cage.
I used to get spasms in my back all the time in high school. My mom had a percussive massager (like the picture below) with two rubber heads that would pound away at the muscle until it relented. It always worked okay on my lower back, but as soon as she ventured up on my rib cage, that thing started bucking like a wild bull. All those bones so close to the surface made it impossible for it to do its job.
Doesn't he look happy to be here? Maybe it's because he has a tad more muscle for the massager to work with.