Changes in oxygenated haemoglobin (oxy-Hb), deoxygenated Hb (deoxy-Hb), and total Hb (t-Hb) in the control group throughout the experiment (no acupuncture stimulation). The values for oxy-Hb, deoxy-Hb, and t-Hb in the stimulation region were each averaged to 10-s intervals. There was no change in any parameters for the control group. OD is optical density. The number of the subjects is 10. Values are represented as means ± S.D.