Failure of transcutaneous electrical nerve stimulation in the conventional and burst modes to alter digital skin...

The purpose of this study was to determine if transcutaneous electrical nerve stimulation (TENS), when applied using stimulation settings that might be used in clinical practice, produces alterations in skin temperature. Stimulation in the conventional and burst modes was applied to the skin of the forearm overlying the median nerve in a healthy human subject. Skin temperature was measured at the index finger, little finger, and on the volar surface of the forearm in the stimulated limb. TENS applied for 20 minutes in the conventional mode at an intensity sufficient to produce a perceptible though not uncomfortable sensation and a slight muscle contraction of the forearm musculature failed to alter skin temperature at any of the three measurement sites. Stimulation using the same pulse characteristics delivered in the burst mode failed to alter skin temperature of the fingers but produced a significant increase in skin temperature at the forearm. The increase in skin temperature at the forearm persisted for four minutes following the cessation of stimulation after which skin temperature returned to prestimulation levels. We conclude that TENS, as applied in this study, does not influence skin temperature in the peripheral distribution of the nerve stimulated, and hypothesize that the rise in skin temperature at the forearm was a result of increased blood flow in the forearm muscles produced by the stimulation-induced contraction of those muscles.