The immediate effect of applying transcutaneous electrical nerve stimulation on sympathetic ganglion and gastrocnemius for popliteal blood flow in healthy adults.

BACKGROUND: The influence of transcutaneous electrical nerve stimulation (TENS) site and frequency on lower-limb hemodynamics remains unclear. OBJECTIVE: To examine the acute hemodynamic effects of high-frequency (80 Hz) and low-frequency (4 Hz) TENS applied to the sympathetic ganglion or gastrocnemius muscle in healthy adults. METHODS: Forty-three healthy adults underwent four TENS protocols combining sympathetic ganglion or gastrocnemius stimulation with high or low frequency. Doppler ultrasonography measured popliteal artery and vein hemodynamics at baseline, during stimulation, immediately after, and 15 min post-stimulation, including vessel diameter (D), flow volume (FV), peak velocity (PV), and TAmax. RESULTS: All four protocols significantly enhanced popliteal arterial and venous hemodynamics during stimulation (p < 0.01). Most parameters returned to baseline after stimulation. However, low-frequency TENS applied to the sympathetic ganglion produced short-term sustained increases in arterial PV (p = 0.03) and elicited greater arterial flow responses than high-frequency stimulation (p < 0.05), with no between-frequency differences in venous parameters (p > 0.05). With gastrocnemius stimulation, popliteal arterial and venous responses were frequency-independent (p > 0.05). CONCLUSION: Both high- and low-frequency TENS applied to the sympathetic ganglion and gastrocnemius muscles acutely enhanced the lower-limb hemodynamics. Low-frequency stimulation of the sympathetic ganglion may induce transient sustained arterial effects.