Kilohertz-frequency interferential current induces hypoalgesic effects more comfortably than TENS

Abstract

Recent research on transcutaneous electrical stimulation has shown that inhibiting nerve conduction with a kilohertz frequency is both effective and safe. This study primarily aims to demonstrate the hypoalgesic effect on the tibial nerve using transcutaneous interferential-current nerve inhibition (TINI), which injects the kilohertz frequency produced by the interferential currents. Additionally, the secondary objective was to compare the analgesic effect and comfort of TINI and transcutaneous electrical nerve stimulation (TENS). Thirty-one healthy adults participated in this cross-over repeated measures study. The washout period was set to 24 h or more. Stimulus intensity was set just below the pain threshold level. TINI and TENS were applied for 20 min each. The ankle passive dorsiflexion range of motion, pressure pain threshold (PPT), and tactile threshold were measured at the baseline, pre-test, test (immediately before ceasing intervention), and post-test (30 min after ceasing intervention) sessions. After the interventions, the participants evaluated the level of discomfort for TINI and TENS on a 10 cm visual analog scale (VAS). As the results, PPT significantly increased compared to baseline in test and posttest sessions of TINI, but not in those of TENS. Also, participants reported that TENS was 36% more discomfort than TINI. The hypoalgesic effect was not significantly different between TINI and TENS. In conclusion, we found that TINI inhibited mechanical pain sensitivity and that the inhibitory effect persisted long after electrical stimulation ceased. Our study also shows that TINI provides the hypoalgesic effect more comfortably than TENS.

Figure 1

The flow diagram of participants.

Figure 2

The electrode placement of transcutaneous interferential-current nerve inhibition (TINI) (a) and transcutaneous electrical nerve stimulation (TENS) (b). The gray squares represent the electrodes.

Figure 3

Ultrasound image for finding the tibial nerve. PA: Peroneal artery, PV: Peroneal vein.

Figure 4

The visual analog scale (VAS) score for the discomfort of electrical stimulation (a). And the ankle dorsiflexion range of motion (ROM) at each condition (b). The data are shown as group means ± standard error. *p < 0.05. TENS: Transcutaneous electrical nerve stimulation group, TINI: Transcutaneous interferential-current nerve inhibition group.

Figure 5

The pressure pain threshold (PPT) at each condition (a: thumb, b: little toe, c: heel, d: calf). The data are shown as group means ± standard error. *p < 0.05. TENS: Transcutaneous electrical nerve stimulation group, TINI: Transcutaneous interferential-current nerve inhibition group.

Figure 6

The tactile threshold (TT) at each condition (a: thumb, b: little toe, c: heel, d: calf). The data are shown as group means ± standard error. *p < 0.05. TENS: Transcutaneous electrical nerve stimulation group, TINI: Transcutaneous interferential-current nerve inhibition group.