Time course of the entire experimental procedure. Each participant was administered the ANT three times: at baseline, after painful stimulation, and after acupuncture. First, all participants were administered the ANT1 without any interruption (Baseline). Then, all were re-administered the ANT2 immediately after painful stimulation (Pain) or after acupuncture (Acu). Lastly, all were re-administered the ANT3 immediately after acupuncture (Acu) or after painful stimulation (Pain). The sequence of Pain and Acu were counterbalanced across all participants. There was a 5-min rest period (R1, R2) after each ANT.