In the physical rehabilitation profession we tend to carry many labels through countless certifications, continuing education and residencies. Despite this large disparity, and growing areas of specializations, there is one thing that MOST choose to label themselves as when asked: "Manual Therapists."
We treat the body, therefore it must make sense that the most important thing we can do is touch the body - be it by means of massage, trigger point release, instruments, or active release techniques.
However, do our claims of treating, or "changing", specific tissue really hold up in this ever changing evidenced based world we live in. This is where the conversation gets interesting. The answer is we probably (still) don't know.
The current theory is that manual therapy either works on a biomechanical level and/or a neurophysiological level. The difficulty is getting research to link the two separate ideologies together.
The shortcomings presented in manual therapy from a mechanical model standpoint may lie in the fact that palpation for specific muscle and movement faults have demonstrated poor reliability. Another reason, I believe, is verbiage - there seems to be poor agreement on correct terminology to aptly describe what we are doing when it comes to manual therapy. Not to mention, even if it was established, we would still be relying on the subjective feeling of each individual provider to make sense of everything. How can you be sure you feel what I feel?
When it comes to force and technique choice - here too seems to be an area where there is little to no agreement, or proof that a specific technique may provide better outcomes. While we have made huge advancements in understanding how cells react to stimulus, there is yet to be an agreement on force, frequency and duration. At the very least we know that tissue adaptation requires repeated stimulus over a period of time - so any outcome we get after one treatment is more then likely to be placebo. Therefore it seems to be important to understand the other element of manual therapy - the nuerophysiological effect.
Some studies have spoke about the pain relieving power of touch/human contact, however if you look deeper it appears that touch may impact levels of cyotkines in the blood, as well as levels of serotonin and endorphins.
It has also been proposed that manual therapy has been shown to lower inflammation with exercise, and decrease substance P levels in patients with fibromyalgia. In addition, and of recent note, functional MRI studies have been attempting to correlate the brain's response to touch and its impact on pain levels. The idea here is that brain activity is limited in an area of pain or injury. Thus through use of mental imagery and manual therapy we can cause an increase in proprioceptive input from these areas in order to help the brain "map" the area and improve function.
Even when we come to an agreement there will always be remaining obstacles such as; placebo response, patient expectation and other psychosocial factors which may affect treatment (one of which is cognitive dissonance). This theory supports the idea that as humans we are programmed to ignore new information when personal beliefs are challenged. Imagine spending your whole life creating and perfecting a manual technique to be told it does not "work". Yeah I might have a hard time accepting that too.
In conclusion, it may end up that we must learn to understand WHO may respond to manual therapy, rather then WHAT will respond to manual therapy. Hopefully that may guide our direction and future research to ensure optimal outcomes with our clients and patients.