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, 200micros) 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.