EMG - Electromyography
An EMG (electromyography) is a diagnostic test that evaluates the health of your muscles and the nerves that control them. It measures the muscle response or electrical activity in response to nerve stimulation. EMG testing is generally performed to diagnose or rule out a muscle disorder or a nerve disorder affecting the muscles. 
How Does EMG - Electromyography Work?
An EMG (electromyography) is a diagnostic test that evaluates the health of your muscles and the nerves that control them. It measures the muscle response or electrical activity in response to nerve stimulation. EMG testing is generally performed to diagnose or rule out a muscle disorder or a nerve disorder affecting the muscles.
Motor neurons are nerve cells that transmit electrical signals that cause your muscles to contract. An EMG test uses small electrodes to transmit these signals to a machine that converts them into graphs, sounds, and numerical values that a neurologist can read and interpret.
EMG testing is performed on muscles at rest, during mild contraction, and during forceful contraction. Normally, muscles do not produce electrical signals at rest. Electrical activity increases with forceful contractions, which produce the highest amount of electrical activity.
What Is EMG Used For?
EMG is one of the diagnostic tools for patients with symptoms of nerve or muscle disorders. Common symptoms leading to EMG testing include:
- Muscle Weakness
- Tingling or Numbness
- Chronic Muscle Pain or Cramping
- Certain Arm or Leg Pain
EMG results generally provide definitive results to confirm or determine a range of muscle or nerve conditions such as:
- Muscle Diseases
- Myasthenia Gravis (MG)
- Carpal Tunnel Syndrome
- Amyotrophic Lateral Sclerosis
- Herniated Spinal Discs
- Polyneuropathies: diabetic, paraneoplastic, medication-related
What to Expect During the Test?
During the EMG recording, depending on your complaints and affected muscles, your neurologist may place surface electrodes at various locations on your skin or insert small needle electrodes into your skin and muscle.
As the electrode measures the electrical activity of your muscle, you can see it on a screen or hear it through a speaker. Your doctor will give you instructions during the test about when to relax your muscles and when and how much to contract them.
How Do I Prepare for EMG?
Take a shower shortly before your test to clean the natural oils from your skin, and do not apply any lotion or cream. Since body temperature can affect EMG results, if you are having the test during winter months, you may need to warm up after arriving for your appointment. Having a full stomach when you come for the test will make you more comfortable. Wear comfortable or easily removable clothing.
If you have a pacemaker, are taking blood thinners, or have hemophilia, inform your neurologist before the test. Pregnant patients can also have the test, but inform your doctor before testing.