NMES
Meaning of NMES: Electrical pulses that make a muscle work when the brain's own signal is too weak or cannot get through.
Definition of NMES
NMES stands for neuromuscular electrical stimulation, a treatment in which small electrical pulses delivered through skin electrodes make a weakened muscle contract. The current activates the nerve supplying the muscle rather than the muscle fibers themselves. It is used to hold on to or rebuild strength when a person cannot work the muscle voluntarily, or cannot work it hard enough.
How does it make a muscle move?
A voluntary movement starts as a signal from the brain that travels down a nerve and ends at the muscle. NMES joins that pathway near its end. Electrodes on the skin deliver brief pulses that set off the nerve, and the nerve then fires as it would have on its own, so the muscle contracts. The nerve running to the muscle must still be intact for this to work. Where that nerve has been cut or destroyed, ordinary NMES has nothing to act on and produces no movement.
How does it differ from TENS?
| NMES | TENS | |
|---|---|---|
| Target | The motor nerve | Sensory nerves |
| Aim | Produce a visible muscle contraction | Reduce the sensation of pain |
| What it feels like | The muscle tightens and releases in cycles | Tingling or buzzing, with no contraction |
The two use similar looking equipment and are easily confused. Acupuncture like transcutaneous electrical nerve stimulation is a further variation aimed at pain rather than at strength.
Where is it used?
NMES is used after joint surgery, when pain and swelling stop a person tightening the thigh muscle properly, and during long stays in intensive care, where muscle wastes quickly in someone unable to move. It is used after a stroke to help lift the foot during walking, and in spinal cord injury to preserve muscle bulk. Making the calf muscles contract also squeezes the deep veins and pushes blood back toward the heart, which supports circulation in a limb that is not being used.
What are the limits?
Electrical stimulation recruits muscle fibers in a different order from voluntary effort, calling on the fatigue prone fibers first, so the muscle tires faster than it would during ordinary exercise. The current also has to cross skin, which stings well before deep muscle is reached, and that discomfort caps how strong a contraction can be produced. NMES is therefore generally an addition to active exercise rather than a replacement for it, and it does not build strength in a healthy muscle the way training does. An implanted pacemaker or defibrillator is among the situations where the current itself is a hazard.
Also known as
Used in a sentence
Neuromuscular electrical stimulation was added to the rehabilitation program after knee surgery.
Good to know
NMES depends on an intact nerve running to the muscle, so it produces no contraction where that nerve has been destroyed, and it recruits fatigue prone fibers first, which limits how long a session can be sustained.