Imai K, et al. Comparison of transient heart rate reduction associated with acupuncture stimulation in supine and sitting subjects. Acupuncture in Medicine: Journal of the British Medical Acupuncture Society 21(4):133-7.

The authors investigated the difference in transient heart rate reduction associated with brief acupuncture in 20 healthy subjects at rest in a supine and in a sitting position.

After the subjects had been at rest for about 20 minutes, the authors performed acupuncture needling using the sparrow-pecking method, in which the needle is moved vertically lifting and thrusting, for one minute at the Shousanli point on the right forearm (LI10). The procedure was carried out with the subjects in a supine position and in a sitting position. The position for stimulation of each subject, either supine or sitting, was selected at random, and on different days.

The results showed that the average heart rate reduction associated with stimulation in supine subjects was 3.6 +/- 0.19 beats per minute (bpm), while that for sitting subjects was about 7.0 +/- 1.07 bpm, indicating that stimulation reduces heart rate to a greater degree in subjects who are sitting. These results would be consistent with a mechanism involving reduced sympathetic drive to the heart, as sympathetic nerve activity has more influence on the heart rate in the sitting than in the supine position.