An electric muscle stimulator is a device used in chiropractic care, physical therapy, and sports medicine.
What is Electric Muscle Stimulation?
Electric muscle stimulation is known also as electromyostimulation or neuromuscular stimulation (or the abbreviations NMES or EMS). Its purpose is to make the muscles contract via electrical impulse. Athletes and people in good health have recently started using this type of therapy for strength training and for recovery after exercise, but it has healthcare purposes as well. For patients who are immobilized, EMS is a “rehabilitation and preventive tool”. It is a tool that is used to “evaluate neural and/or muscular function in vivo”, as well. The electric muscle stimulator works by placing electrodes (generally in the form of pads) on the skin near the muscles that are to be stimulated. Impulses are created with the electric muscle stimulator machine, and they “mimic the action potential coming from the central nervous system”. The muscles contract due to the impulses. Sports scientists have lately been citing that EMS is a “complementary technique for sports training”. Recent research has also been published on electric muscle stimulator usage in sports and exercise. Historically, it was Luigi Galvani who, in 1791, provided evidence that muscles can be activated by current. In the 19th and 20th centuries, it was found that functions in the body that were “induced by electrical stimulation caused long-term changes in the muscles”. Soviet scientists used electrical muscle stimulation in athletes in the 1960s. In the most recent research in physiology, “the mechanisms by which electrical stimulation causes adaptation of cells of muscles, blood vessels, and nerves” were pinpointed. EMS is now known to cause muscle fiber adaptation and training. Since muscle fibers vary, different fiber types can be “activated to differing degrees”, so electric muscle stimulator protocols differ. Some of the programs aim to work on endurance, or fatigue resistance, and others might increase “force production”.1
Electric muscle stimulator devices are used therapeutically, for training, and even for cosmetics. Strengthened muscles look good, so some practitioners use EMS for aesthetic purposes; however, “the FDA rejects certification of devices that claim weight reduction”. The weight loss or calorie burning is “marginal at best”, but some suggest EMS will make people want to exercise after the body appears more toned. In the medical field, EMS is used in physical therapy rehabilitation to help prevent muscles from atrophying due to lack of use. When muscles, ligaments, joints, bones, and tendons are damaged in musculoskeletal injuries, electrical muscle stimulation can be useful. Transcutaneous electrical nerve stimulation by TENS units (electric muscle stimulation devices) are utilized in pain therapy. Some people purchase “non-professional devices” for home use. Ab toning belts are one such example of this. The FDA certifies two categories of devices: prescription and over-the-counter. OTC electrical muscle stimulator devices are marketed for toning muscles, while medical devices are purchased only with a prescription and should be used under authorized practitioner supervision. These prescription devices are utilized to increase blood circulation, relax spasms, prevent atrophy, to re-educate muscles, to assist range-of-motion, and post-surgically in the calf to “prevent venous thrombosis”. EMS devices should not be used in people who wear pacemakers, and they should not be placed on vital body parts (“carotid sinus nerves, across the chest, or across the brain”). Caution is advised for menstruating or pregnant women and for people with certain medical conditions. Possible adverse effects include burns and skin irritation.2
TENS or “e-stim” can be used for pain relief. There are a couple of theories about the mechanisms behind this. One theory, Gate Control, suggests that any pain signals sent over to the brain through the nerves have to “pass through a ‘gate’”. The e-stim makes it through the gate and blocks pain nerves. The second theory has to do with the “body’s natural painkillers—endorphins and enkephalins”. These chemicals increase after electrical stimulation. There is some controversy in the research in that some studies have found little benefit to EMS compared with a placebo. As a result, electrical stimulation has been considered “alternative medicine”. Other studies have found that people with acute pain had a significant reduction in the pain’s severity after use of the electric muscle stimulator. This therapy is not addictive and the devices are easy to use. Instead of taking pain medications, e-stim is cost-effective and does not carry the same side effects. TENS units “will not solve the underlying condition” and even for “muscle re-education…it can cause a muscle to contract (but) function may not return if the…damage is severe”. E-stim will also not cause “significant strength gains”.3
Chiropractors and physical therapists use EMS or “muscle stim” to strengthen muscles, deal with inflammation, and for pain control. First, the patient is hooked up to the machine by having electrodes placed around the parts of the body that are affected, such as the wrist, knee, ankle, shoulder, back, and neck. Electrodes are placed in locations based on the reason for the muscle stim and how “deep or superficial” the current needs to go. The stim machine is adjusted until the patient feels a “prickly sensation”, but it should only be set to a comfortable tolerance level and not one in which the patient feels stabbing, burning, or stinging. Overworking muscles causes more problems. The therapy is meant to control inflammation and “enhance tissue healing” by increasing the circulation and decreasing swelling. It could also “block nerve transmission at the spinal cord”, which may provide a reduction in pain.4 Besides muscle atrophy prevention, EMS can be used in patients with osteoarthritis to improve mobility and help with physiotherapy. The therapy can even reduce the possibility of pressure sores in patients who are bound to beds or wheelchairs.5 The electric muscle stimulator could be beneficial for promoting muscle tone and speeding healing.6 The contractions it causes releases endorphins, but it also is designed to fatigue muscles, allowing them to relax, and for abating spasms.7 EMS can even be utilized to alleviate headaches, back and neck pain, and shoulder pain. When chiropractors use the stims, ice packs are “placed over the electrodes to further ease the pain and reduce the swelling”.8
Types of Electrotherapy
There are really several different types of electrical stimulation devices available, including TENS, but also interferential current (IFC) and galvanic stimulation (GS). All use adhesive pads on the skin to apply electrical stimulation the muscles and nerves. Side effects of the electric muscle stimulator are rare, but some patients have an allergic reaction on the skin to the pads, some pain from the charge, and those with heart conditions could have an arrhythmia. Electrical stimulation should not be used for certain patients or on infected or malignant areas. TENS is the most common therapy. IFC is a “deeper form of TENS”, and GS is “most useful in acute injuries associated with major tissue trauma”. Unlike IFC and TENS, which use “alternating current”, the GS therapy applies “direct current”.9 Chiropractic offices may offer any of these types of electrical therapies. IFC can be used to aid in healing by reducing spasms and pain, releasing endorphins, and improving lymphatic drainage, blood flow, and “sensory fiber stimulation”.10 GS, with its direct current, is thought to change blood flow, with the use of a positive and a negative pad. The positive pad is meant to act like ice and reduce swelling and circulation, while the negative pad provides heat to speed healing and increase circulation.11