FAQ

What is EMG?
The letters EMG represent “electromyography,” which refers to the measurement of muscle electrical activity. As muscles contract, microvolt level electrical signals can be measured from the skin's surface. Electromyography is the study of muscle activity through the measurement of these electrical signals. Researchers and clinicians use surface EMG to more accurately evaluate muscle function and activity.
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What is the difference between needle EMG and surface EMG?
Needle EMG is performed with a needle electrode penetrated through the skin and directly into the muscle. This provides information about a single muscle fiber rather than information on the overall condition of a muscle. Surface EMG technology allows information regarding the overall muscle function and condition to be collected from the surface of the skin. This process is non-invasive and non-painful to the patient.
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How does Noraxon surface EMG work?
Sensors placed on the skin directly above the muscles detect the small electric potential, or signal, which comes from active muscles. The strength and pattern of the signal is displayed on 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.
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Why is Noraxon signal conditioning superior?
For data to be reliable and valid, the signal must be virtually artifact-free. If it is not, then the data is often unreliable or invalid, which renders it useless. The Noraxon signal conditioning system uses an electronic feedback technique to cancel out very low frequency changes (dc to a few Hz) in the acquired physiological signal. Signals in this very low frequency range can arise because of the motion artifact phenomena. The Noraxon signal is remarkably free of noise caused by skin or cable movement and offers a very stable baseline. With Noraxon's patented system, information carried by the overall signal is effectively split into an "EMG only" component and a low-frequency "motion artifact" component. The motion artifact component is literally subtracted from the overall signal allowing only the EMG signal to be presented.
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How long does it take to setup?
The initial setup takes approximately 15 minutes. Once the equipment is setup, it is ready to be utilized for each subsequent session. Any additional setup time for each patient is in the placement of the electrodes.
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How do you know where to place the electrodes?
Electrode placement requires the user to be able to locate and identify the superficial muscles of the body. Electrodes are placed on the muscle belly, parallel to the grain of the muscle fibers. Noraxon provides several reference guides relating to proper placement of electrodes. An introductory guide, “SEMG Made Easy” is available for purchase and protocol documents are accessible within our software systems. Also, with the use of Noraxon’s data acquisition and analysis software (MyoResearch XP), muscle maps are built into the program to help determine the proper location of electrode placement.
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How can the use of SEMG help me as a clinician?
SEMG assists the clinician in making treatment decisions by (1) identifying whether a muscle is working excessively or not recovering from activity, (2) determining if a specific exercise is recruiting the desired muscle appropriately, and (3) determining whether compensation is occurring during functional activities, based on quantifiable, objective data.
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Can SEMG be used during therapy?
Yes. A patient may be connected during a regular therapy session. Noraxon's SEMG allows patients to "see" the results of their efforts on a computer screen as they perform. This encourages the patient when striving to attain proper muscle recruitment.
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Can I get reimbursed for the use of SEMG in treatment?
Yes, there are several codes that may be used for surface EMG evaluations and biofeedback. You may refer to a CPT Codes manual or view Clinicians Billing Resources as a reference for codes used in conjunction with surface EMG.
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Can SEMG be used in conjunction with other equipment?
Yes. It can be used with other analog output devices, such as force plates and isokinetic devices.
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Do you have to perform separate tests in order to assess symmetry, fatigue, timing, and/or coordination?
No. Various analyses can be performed on the same data set.
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If you have further questions, contact Noraxon toll free at (800) 364-8985 or (480) 443-3413.