Humans evolved to heal one another. As long as our bodies run on time-varying signals, we benefit from exposure to reference signals better than (or at least different from) our own. The same principles one would use to collectively tune musical instruments or calibrate scientific instruments apply to us as well. We need to sense the vibrations of other humans, especially touch.
But not just any touch. The fact that touch does carry information means that some touch can be bad, and some good. The intention and intuition of a practitioner matters as much as her formal skills. The intention of the recipient matters even more, so that an un-cooperative patient may not benefit at all. These variables absolutely exist in a neuro-mechanical view of bodies, but such subtle vibrational influences are hard to understand, much less measure.
So the best way to choose a bodyworker is by personal recommendation from someone whose judgement you respect, and the best way to use a bodyworker is to invite that person to do what she thinks is necessary, and to be grateful for her attention.