All About EMG



noun:   the recording of the electrical activity of muscle tissue, or its representation as a visual display or audible signal, using electrodes attached to the skin or inserted into the muscle.


What is Surface EMG (SEMG)

As muscles contract, microvolt level electrical signals are created within the muscle that may be measured from the surface of the body. A procedure that measures muscle activity from the skin is referred to as surface electromyography (SEMG).

Researchers and clinicians use SEMG to evaluate the functional status of skeletal muscles and assist inneuromuscular training and rehabilitation. The small electrical current, or signal, which comes from active muscles, is detected by sensors placed on the skin directly above the muscles. The strength and pattern of the signal is displayed onto a computer screen and the data is collected in a software program that is able to run various analyses of the data to create useful reports regarding muscle function.

Because SEMG signals are small, their measurement is susceptible to interference – for example, from electrical equipment, lights or movement of cables that carry signals from the body to the measuring instrument. Evaluations require the subject to perform a full range of movement exercises and interference from movement of lead wires has been a problem.

Lower cost instruments attempt to eliminate artifact by electrode site pre-amplification and by “notching out” or filtering the frequencies at which interference occurs. Unfortunately, these frequencies are also where most SEMG signals are located. Devices that use “notch-filtering” lose essential data. That is why accurate, reliable SEMG measurement was impossible – until Noraxon.

Noraxon’s breakthrough amplifier technology actually distinguishes between SEMG signals and artifact. The result is reliable, repeatable and pure SEMG data that enables professionals to make more precise evaluations of muscle activity and performance. This is the secret behind all Noraxon systems.

Discovery Channel: EMG and Neurology