In 14 healthy female subjects, the effects of acupuncture on skin and muscle blood flow were investigated using a non-invasive custom-designed probe and photoplethysmography (PPG). In randomized order, two to seven days apart, three modes of needle stimulation were performed on the anterior aspect of the tibia: superficial insertion (SF), insertion into the anterior tibial muscle (Mu), and insertion into the muscle including manipulation of the needle in order to elicit a distinct sensation of distension, heaviness or numbness (DeQi).

Compared to the control situation, muscle blood flow increased following both Mu and DeQi for 20 min, with the latter being more pronounced for the initial 5 minutes. Skin blood flow increased for 5 min following DeQi. However, no increase was found following SF. The results indicate that the intensity of the needling is important, since the DeQi stimulation resulted in the most pronounced increase in both skin and muscle blood flow.