EMG is a test that assesses disorders of muscles and the nerves controlling them. A doctor performs this test.

For an EMG, a needle electrode is inserted through the skin into the muscle. The electrical activity detected by this electrode is displayed on a monitor.  This is usually performed after a nerve conduction study.

You may be asked to contract the muscle (for example, by bending your arm) which will give the doctor information about how muscles respond to messages from nerves.

 

There may be some discomfort with the insertion of the electrodes (similar to an injection into a muscle). Afterwards, the muscle may feel tender or bruised for a few days.

 

There is a very low risk of bleeding or infection at the site of the needle but this is minimal.

 

EMG is most often used when people have symptoms of weakness and examination shows impaired muscle strength. It can help to tell the difference between problems with a muscle versus problems with the nerves supplying the muscle.