Dr. Kyle Ridgeway, DPT is a reader and often writes very insightful and thought provoking comments after my posts. I thought I would take one of his better posts and comment on it from my perspective. I used his comment with permission to create the discussion. Anyone else want to chime in?
Follow Kyle at @PTThinkTank on his blog PT think Tank.
When it comes to individuals with a primary complaint of pain, our manual therapy effects are most likely much more nervous system mediated than mechanically mediated. The force and duration of our treatments make permanent mechanical changes very unlikely. Movement and exercise performed for painful conditions are also likely causing neuro-physiologic effects resulting in decreased pain and increased mobility. In short, they are decreasing the perceived threat level and causing a decreased pain output. Someone who has low back pain and receives mobilization, manipulation, or soft tissue work, or any other kind of hands on treatment is experience decreased pain because of nervous system effects, NOT mechanical changes in their tissues. Take also an example of someone who has "tight" hamstrings and performs hamstring "stretching" is likely just increasing their nervous system's tolerance (both PNS and CNS) to stretch/ROM, NOT increasing the length of their hamstring tissue. Now, the result is that they are more "flexible" but those effects are likely nervous system mediated not mechanically/tissue mediated.
I only partially agree with you. Every treatment administered to a pt definitely affects the nervous system. Education, movement, exercise, and manual therapy all can decreased the perceived threat. However, when it comes to rapid changes, the current pain research is ignoring something as simple as MDT's directional preference (DP). If there was less of a mechanical effect, then something like repeated flexion in standing would not peripheralize and worsen the complaint and repeated extension in standing would not centralize and improve the complaint. MDT has studies showing repeated extension reducing a disc protrusion, which would improve the ROM quickly from a mechanical perspective.
Another example is a manipulation to improve a positional fault that is palpable (unreliably so) and Mulligan tibial internal rotation improving knee flexion, but trying the same thing with external rotation, and having it flare up the patient's knee. Your evaluation helps choose the appropriate technique to relieve the pain during the movement which then decreases the perceived threat from a neurologic perspective.
I normally spend 20-30 minutes doing manual on a patient, sometimes forceful, sometimes just enough to elicit a change. I always test pre and post, function, special test, or ROM. The IASTM and manual techniques I choose are designed to make a rapid change. I do not increase the length of muscles in that time, as you cannot grow sarcomeres that quickly, but I most like am changing type III collagen PLUS eliciting neurologic changes.
Either way, the HEP I prescribe involves frequent and repeated movement into the new range, thus educating the brain that the movement doesn't have to be painful, plus preventing the viscoelastic tissues from adhering and keeping some of the remodelling from the manual techniques.