What is the arthrokinetic reflex and what does it have to do with strength, mobility, flexibility and joint mobility drills? Here is a (very) quick explanation.
The arthrokinetic reflex defined
Arthro means joint. Kinetic means movement. Reflex means involuntary movement in response to a stimulus. Put them together and you have a term coined by researchers in the 1950s as a way to describe the idea that sensory input from joint movement can reflexively cause activation or inhibition of certain muscles.
This theory was proposed as way to explain the results of an experiment where scientists deactivated a cat's brain but were still able to effect muscle tone changes in the legs by moving the knee. Similar results were found in a different study involving the muscles of the jaw. The researchers concluded that abnormal jaw positions resulted in mechanoreception that reflexively created abnormal (and dysfunctional) patterns of muscular activation.
The arthrokinetic reflex and strength
Dr. Eric Cobb, the creator of Z-Health, uses this term as a way to explain why joint mobility drills may be a quick and easy way to increase strength, flexibility or coordination. The idea is that moving a joint alters the mechanoreceptive information coming from the joint, which can reflexively alter the activation of the muscles attaching to the joint. For example, there is at least one study where hip mobilization led to immediate increases in hip abductor strength.
But is this the result of the arthrokinetic reflex or some other neural mechanism? I don't know if there is any answer to this question, but personally I don't care that much. Mechanoreceptive information might end up talking to many different areas of the spine and brain, all of which might have some sort of influence, reflexive or otherwise, on how the muscles around that area should be activated in the near future.
If the sensory information basically conveys the idea that movement in the joint is safe, we should expect the nervous system to loosen its governor on strength, speed and range of motion. If the information suggests that the movement in question involves danger, we should expect increased protective activity, such as stiffness, pain, weakness, and altered coordination.