Conventional TENS treatment
A typical TENS machine was used (GEM-STIM GM3A5XT, Chi-Mao Co., Taiwan) to delivered conventional TENS treatment. Two adhesive round electrodes (2.5 cm radius) were applied to the same treatment positions, as described above. Negative electrodes were placed on the carpal ligament (covering PC-6), and positive electrodes were placed on the distal pulp of index (covering the hand acupuncture point of the wrist). The device delivered asymmetric biphasic pulse current, and the parameter was set at a pulse rate of 30 Hz frequency and a stimulation period of 70 μs, which were similar to the AcuLife device. The device provides two channels output and enable bilateral treatment simultaneously. One TENS session lasted for 15 min, and at least a total of 30 sessions (5 sessions per week) were completed.