Electromyography (EMG) measures the electrical activity of muscles during rest and contraction and is used to help detect neuromuscular abnormalities.

During the test a small needle is inserted through the skin into the muscle. The electrical activity picked up by the electrodes is then displayed on an oscilloscope (a monitor that displays electrical activity in the form of waves). An audio-amplifier is used so the activity can be heard.

• Eat and drink normally before the study. Fasting is not required.

• Dress in clothes that allow access to the area to be tested - clothes that can be easily rolled up to expose most of the arm or leg being tested. You will be provided with a gown if clothing needs to be removed.

• Avoid the use of skin moisturisers prior to the test.

• You do not need to with-hold any of your medications but let the doctor know if you are on anticoagulants such as warfarin, dabigatran or rivaroxaban.

• Tell your neurologist if you have a cardiac defibrillator or pacemaker.

It takes up to 30 minutes.

The EMG is usually performed immediately following a nerve conduction study.

1. Having identified the nerves to be studied the neurologist will locate the associated muscle(s) to be studied.

2. A fine, sterile needle will be inserted into the muscle. A ground electrode will be positioned on your arm or leg.

3. Five or more needle insertions may be necessary for the test. You may experience slight pain with the insertion of the electrode.

4. You will be asked to relax and then perform slight or full-strength muscle contractions.

5. The electrical activity from your muscles will be measured and displayed on the oscilloscope.

6. An audio amplifier may also be used so that both the appearance and sound of the electrical potentials can be evaluated. If the recorder is attached to an audio amplifier, you may hear a sound like hail on a tin roof when you contract your muscles.

Some muscle soreness may persist for a day or so following the procedure. Notify your GP if you experience increasing pain, tenderness or swelling at the needle insertion sites.