During acupuncture treatment, acupuncture needles are inserted and manipulated until a characteristic local tissue reaction termed "de qi" is observed. De qi can be perceived by the acupuncturist in the form of "needle grasp", a mechanical gripping of the needle by the tissue. De qi is considered essential to the therapeutic effect of acupuncture. Therefore, the investigator proposes that understanding this local tissue reaction will lead to an understanding of how the therapeutic effect of acupuncture therapy arises. Specifically, it is hypothesized that needle manipulation causes winding of collagen and elastic fibers around the needle. This action induces tension in the collagen network surrounding the needling site and results in a mechanical signal that is transduced into local cells. The objective of the current work is to use ultrasound elastography, a recently developed ultrasound imaging technique, to visualize and quantify changes in the elastic properties of skin and subcutaneous tissue in 12 healthy human volunteers as a result of acupuncture needle manipulation.