A commonly expressed opinion is that needle grasp is due to contraction of skeletal muscle when needled at a motor point or neurovascular hilus, but so far no published data have conclusively supported this model. In contrast, needle grasp is an observable phenomenon consisting of a change in the mechanical interaction between the needle and surrounding tissue. Since needle grasp is an integral component of de qi, measuring pullout force may be an important step to understanding the role, if any, played by classically defined acupuncture points in acupuncture therapy. We are currently performing a study in which we are measuring pullout force at 8 acupuncture points and 8 corresponding contralateral control points in 80 normal human subjects. A novel and important aspect of this study is that all acupuncture needles are inserted, manipulated and pulled out using a computer-controlled mechanical instrument.
Pullout force is measured automatically by the instrument as the needle is pulled out of the skin.
This ensures controlled experimental conditions and eliminates sources of investigator bias. At each point, needle insertion depth is set in proportion to subcutaneous tissue thickness as determined by ultrasound. The same depth is used for corresponding acupuncture and control points. A secondary research question addressed in our study is whether the method of needle manipulation influences needle grasp. The acupuncture vs. control comparison is made within subjects, with acupuncture and control points randomized to right and left sides of the body.