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How Does an EMG Machine Work?

An EMG machine, or electromyograph, captures the electrical signals that muscles emit when they contract. Tiny electrodes, when placed on the skin or inserted via needle, detect these signals, which are then amplified and translated into graphs or sounds by the machine. This process unveils the health of muscles and nerves. Intrigued? Discover how this technology could impact your understanding of muscle function.
Marco Sumayao
Marco Sumayao

Electromyography (EMG) helps detect possible abnormalities in the human body by recording electrical impulses created by muscular activity for medical analysis. There are two general types of EMG machine: surface and intramuscular. Surface EMG detects activity through electrodes placed on the surface of the skin. An intramuscular EMG machine, on the other hand, detects activity through needles inserted directly into the muscle. The degree of invasiveness and resulting sensitivity of the two methods allow for different medical applications.

An EMG machine measures the size, frequency, and general shape of motor unit potentials generated by the patient's movement. When a motor neuron innervates muscle fibers, a slight electrical discharge is emitted from the neuron into the muscle fibers. An electromyograph can detect the sum of this activity and record it for interpretation. EMG tests record the activity both when the muscles are at rest and when the patient contracts them. In order to get accurate measurements, experts usually collect anywhere from 10 to 20 readings before ending the test.

An electromyograph is an instrument for observing the electric activity of muscle fibers and motor neurons.
An electromyograph is an instrument for observing the electric activity of muscle fibers and motor neurons.

A surface EMG machine works by placing electrodes onto the patient's skin, secured by adhesive patches. These electrodes are connected to fine wires that relay any electrical stimulation they receive from the body back to a device that can register and record the impulses. Technicians can then interpret the readings and identify any unusual activity.

An EEG involves the use of electrodes attached to the skin for recording electrical impulses while an EMG involves the insertion of needles into the muscles that will be tested.
An EEG involves the use of electrodes attached to the skin for recording electrical impulses while an EMG involves the insertion of needles into the muscles that will be tested.

An intramuscular EMG machine, on the other hand, is more invasive and involves the insertion of needle electrodes into the patient's skin. Readings can immediately be taken as the needle penetrates the skin and can provide valuable insight into the patient's muscle activity. Since the electrodes can measure motor unit potentials at a closer proximity, intramuscular EMG is usually much more accurate and in-depth than surface EMG. At times, the sensitivity of the measuring device can be deemed unnecessary for tests requiring simpler diagnoses.

Electromyography may be used to diagnose carpal tunnel syndrome and other repetitive stress injuries.
Electromyography may be used to diagnose carpal tunnel syndrome and other repetitive stress injuries.

Electromyography can help doctors determine whether or not patients have certain disorders, and if the causes are muscular or neurological in nature. Muscular disorders usually exhibit low-amplitude readings as a result of decreased muscle activity, while neurological disorders have typically higher amplitudes due to the re-firing of motor neurons. EMG tests are often recommended for patients experiencing tremors, loss of muscle control, or unusual muscle weakness in order to diagnose the causes of these abnormalities. Athletic trainers can also use an EMG machine to track the physical development of their clients and adjust their workouts according to the findings.

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    • An electromyograph is an instrument for observing the electric activity of muscle fibers and motor neurons.
      By: kateryna zakorko
      An electromyograph is an instrument for observing the electric activity of muscle fibers and motor neurons.
    • An EEG involves the use of electrodes attached to the skin for recording electrical impulses while an EMG involves the insertion of needles into the muscles that will be tested.
      By: Tobilander
      An EEG involves the use of electrodes attached to the skin for recording electrical impulses while an EMG involves the insertion of needles into the muscles that will be tested.
    • Electromyography may be used to diagnose carpal tunnel syndrome and other repetitive stress injuries.
      By: waxart
      Electromyography may be used to diagnose carpal tunnel syndrome and other repetitive stress injuries.