Transcutaneous Electrical Nerve Stimulation (TENS) vs. Neuromuscular Electrical Stimulation (NMES) Brian Gilmer, MD Introduction Transcutaneous Electrical Nerve Stimulation (TENS) and Neuromuscular Electrical Stimulation (NMES) are both electrotherapy techniques. While their application involves the use of electrical stimulation, their purposes and mechanisms of action are distinct. TENS is primarily used for pain relief, leveraging low voltage electrical currents delivered via electrodes placed on the skin to manage pain, particularly chronic pain. The electrical pulses are believed to disrupt pain signals being sent to the brain and stimulate the production of endorphins, the body’s natural painkillers. NMES, conversely, is employed for muscle rehabilitation. It uses electrical pulses to stimulate muscle contraction, which can strengthen weak or atrophied muscles, improve muscle tone and blood circulation, and induce muscle relaxation.
Mechanisms of Action TENS works on two theoretical pain models: the Gate Control Theory and the Endorphin Release Theory. In the Gate Control Theory, TENS is believed to stimulate non-painful sensory nerve fibers, which carry their signal faster than pain fibers. This effectively “closes the gate” in the spinal cord’s dorsal horn, preventing the transmission of pain signals to the brain. In the Endorphin Release Theory, TENS is thought to stimulate the release of endorphins, the body’s natural painkillers, which bind to opiate receptors in the brain to reduce the perception of pain. NMES, on the other hand, uses electrical impulses to mimic the action potential coming from the central nervous system, causing muscle contraction. It does so by depolarizing the motor nerves with a higher frequency current, initiating a muscle contraction. This can lead to muscle strengthening, improved blood circulation, and muscle relaxation. Indications TENS is typically used for chronic pain conditions such as arthritis, back pain, fibromyalgia, and acute conditions like labor pain or post-surgical pain.
NMES is commonly used in physical rehabilitation programs for muscle re-education after injury or surgery, prevention of muscle atrophy during prolonged periods of immobilization, improving range of motion, reducing edema, and promoting wound healing. Contraindications Both TENS and NMES should not be used by individuals with a pacemaker or other type of electrical or metal implant. They’re not recommended for use during pregnancy, except under medical supervision, and NMES should not be used over carotid sinus nerves, particularly in patients with a sensitivity to the carotid sinus reflex. Effectiveness Both TENS and NMES have been shown to be effective in their respective applications. The effectiveness of TENS for chronic pain management is still being explored, but many patients report significant pain relief. NMES has been proven effective in various studies for improving muscle function and strength.
