Immediate Effects of Transcutaneous Electrical Nerve Stimulation and High Voltage Pulsed Stimulation on Subacromial Pain and Shoulder Movements

Transcutaneous electrical stimulation (TENS) and high voltage pulsed current/stimulation (HVPS) are both electrotherapeutic agents which can be used for pain relief in musculoskeletal conditions. Standard TENS devices usually deliver biphasic pulsed currents with a pulse duration between 50 μs and 1000 μs and pulse frequencies between 1 and 250 pps. HVPS devices are TENS-like devices which deliver direct current with twin monophasic spiked pulses of 10-500 V (500-ohm load) with a short pulse duration (microseconds). In both conventional TENS technique and HVPS for pain relief, the aim is to activate spinal gating mechanism by selectively stimulating large diameter Aβ fibers. Theoretically, high-frequency (~10-250 pps), low-intensity (nonpainful) currents are most efficient in selectively activating Aβ fibers, which is practically recognized by the user reporting 'strong but comfortable' nonpainful electrical paresthesia beneath the electrodes. There is no available evidence for the efficacy of TENS in patients with subacromial pain. Also, there has been little experimental work on the effects of HVPS on pain relief in the literature, as well as no known study for its efficacy in SAPS.