The impact of asynchronous electroacupuncture stimulation duration on cold thermal pain threshold.

The durations of asynchronous electroacupuncture can affect the resultant hypoalgesia. Healthy volunteers were randomized to receive different durations (0 min, 20 min, 30 min, or 40 min) of asynchronous electroacupuncture stimulations (alternating low/high [2/100 Hz] frequency at 5 mA). Using a human experimental cold thermal pain threshold model, we found that 30 min of asynchronous 2/100 Hz stimulation resulted in the most significant hypoalgesic effect that was sustained for at least 60 min after stimulation compared with 0-, 20-, or 40-min stimulations (P < 0.05). We conclude that the most optimal duration for asynchronous electroacupuncture stimulation is 30 min.