2.2. Acupuncture Needles
We used three types of stainless needles for double blinding (Confidence Co., Ltd., Tokyo, Japan): (1) penetrating needles that can pierce the skin to a 5 mm depth; (2) skin-touch placebo needles, the tip of which can press against the skin but cannot penetrate it; and (3) no-touch placebo needles, the tip of which cannot reach the skin [