Transcutaneous electric nerve stimulation: The effect of intensity on local and distal cutaneous blood flow and skin temperature in healthy subjects

Objective: To determine what effect transcutaneous electric nerve stimulation (TENS) intensity has on local and distal cutaneous blood flow and skin temperature. Design: Double-blind conditions. Setting: University research laboratory. Participants: Forty subjects (20 men, 20 women) randomly assigned to 1 of 4 groups (10 per group): control, above-motor-threshold TENS, below-motor-threshold TENS, or perception-threshold TENS. Intervention: TENS (4Hz, 200mus) was applied over the median nerve of the right forearm for 15 minutes. Main Outcome Measures: Blood flow measured by laser Doppler flowmeter and skin temperature measured by skin thermistor were recorded during TENS and for 15 minutes after it. Results: Significant differences occurred between groups for forearm (P <.0001; repeated-measures analysis of variance) but not fingertip cutaneous blood flow. Post hoc Fisher tests showed a significant increase in forearm blood flow during TENS application in the above-motor-threshold TENS group compared with the other 3 groups. No significant differences between groups for skin temperature data were observed. Conclusions: The effect of TENS on cutaneous blood flow depends on whether muscle activity is induced. Low-frequency TENS applied above the motor threshold significantly increases local cutaneous blood flow. There were no significant differences between groups for skin temperature.