Electromyography (EMG) measures the response of muscles and
nerves to electrical activity. It's used to help determine
muscle conditions that might be causing muscle weakness,
including muscular dystrophy and nerve disorders. How Is an EMG
Done? Muscles are stimulated by signals from nerve cells called
motor neurons. This stimulation causes electrical activity in
the muscle, which in turn causes the muscle to contract or
tighten. The muscle contraction itself produces electrical
signals. For the purpose of EMG, a needle electrode is inserted
into the muscle (the insertion of the needle might feel similar
to an injection). The signal from the muscle is then transmitted
from the needle electrode through a wire (or more recently,
wirelessly) to a receiver/amplifier, which is connected to a
device that displays a readout. The results are either printed
on a paper strip or, more commonly, on a computer screen. What
Can an EMG Diagnose? EMGs help diagnose three kinds of diseases
that interfere with normal muscle co