How It Is Done
An EMG is done in a hospital, a clinic, or a doctor's office. It may be done in a room that stops any outside electrical activity that can interfere with the test.
You will be asked to lie on a table or bed. Or you may sit in a chair that leans back so your muscles are relaxed.
Electromyogram
The skin over the areas being tested is cleaned. A needle electrode is put into a muscle. The electrode is attached by wires to a recording machine.
When the electrodes are in place, the electrical activity in that muscle is recorded while the muscle is at rest. Then the technologist or doctor asks you to tighten (contract) the muscle slowly and steadily. This electrical activity is recorded.
The electrode may be moved a number of times. This is done to record the activity in different parts of the muscle or in different muscles.
The electrical activity in the muscle is shown as wavy and spiky lines on a video screen. It may also be heard on a speaker. You may hear popping sounds like a machine gun when you contract the muscle. The activity may also be recorded on video.
When the test is done, the electrodes are removed. The places where a needle was put in the skin are cleaned.
Nerve conduction studies
In this test, several flat metal-disc electrodes are attached to your skin with tape or a paste. An electrode that puts out electric pulses is placed right over the nerve. Then a recording electrode is placed over the muscles controlled by that nerve. Several quick electrical pulses are given to the nerve. The time it takes for the muscle to contract in response to the electrical pulse is recorded. The speed of the response is called the conduction velocity.
The same nerves on the other side of the body may be studied. The results from both sides of the body can be compared. When the test is over, the electrodes are removed.
Nerve conduction studies are done before an EMG if both tests are being done.
How long the test takes
- An EMG may take 30 to 60 minutes.
- Nerve conduction tests may take from 15 minutes to 1 hour or more. It depends on how many nerves and muscles your doctor tests.