Pain results in motor impairment, not the other way around.

Pain results in motor impairment, not the other way round. 
"Our study demonstrated that simply inducing experimental pain over the posterior sacro-iliac ligaments in painfree people resulted in the kind of findings often reported in patients with pelvic pain; a positive active straight leg raise (ASLR) and muscle guarding. This indicates that pain alone, regardless of the position or mobility of the pelvic bones, can mimic the clinical findings previously associated with ‘pelvic instability’ or lack of ‘ force closure’. The findings have implications for how we interpret what we find among patients in the clinic. It has often been assumed that these findings when present in patients with pain are the cause of their pain. In contrast, these findings suggest the opposite – that simply experiencing pain causes the body to move in slightly unusual ways, and these are signs of pain, not necessarily the cause of pain."

"This study demonstrates for the first time that pain and hyperalgesia arising from a structure superficial to the sacroiliac joint complex increases the subjective effort, activity in stabilizing muscles, and lifting quality during the active straight leg raise test. Moreover, the pain caused by hypertonic saline is related with the increase in perceived difficulty and muscle activity during the test. These data indicate that pain and hyperalgesia per se can give similar responses to the ASLR test as seen in different clinical groups and challenge the diagnostic value of the test." 

I *love* when my confirmation biases find outside confirmation! 

Now, substitute "pain caused by hypertonic saline" for "nociceptive input from a nerve, cutaneous or motor, but probably cutaneous, that can't drain and is backed up with its own metabolites because of mechanical deformation of its venous drainage coupled with the fact nerves have no lymphatics", and I think this paper is onto something.





Also, don't miss the brilliant chiro-turned-PT, Greg Lehman's, presentation (see above) which deftly deconstructs the biomechanical model in a way that it doesn't even know that it's been sliced to ribbons until it tries to stand up and falls down in a million pieces.








Palsson TS, Hirata RP, Graven-Nielsen T. Experimental Pelvic Pain Impairs the Performance During the Active Straight Leg Raise Test and Causes Excessive Muscle Stabilization. Clin J Pain. 2014 Aug 12.

Just in case you may have missed the point:

Downfall of the biomechanical postural structural model