Fig. 2

a Representative traces of heart rate responses obtained from the control group and acupuncture stimulation groups at the lower leg, ear, abdomen, and forearm. Stripe bars denote the duration of the acupuncture stimulation. b Heart rate averaged during the pre-stimulation baseline period (− 1 to 0 min) and the acupuncture stimulation period (0–2 min). Values are the mean ± standard deviation. *p < 0.05 by the paired t test