EMG muscle scanning: stability of hand-held surface electrodes |
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Authors: | J M Thompson R P Erickson K P Offord |
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Institution: | Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota 55905. |
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Abstract: | Electromyographic (EMG) muscle scanning measures 2-second samples of integrated muscle action potentials from individual neck and back muscles using a hand-held scanner with post-style surface electrodes separated by a fixed distance. This "scanning" technique is widely used to expeditiously assess muscle activity in the diagnosis of musculoskeletal disorders. In order to determine if the 2-second sample is sufficiently representative of electrical activity at a specific muscle site, the stability of the signal received by the hand-held scanner was measured bilaterally at six neck and back muscle sites over 40 seconds (20 2-second integration periods) in five seated subjects. Taking the overall average EMG activity as the "true" value, the mean number of 2-second integration periods required to achieve less than 5% standard error was calculated to be 1.47 for the 60 muscles tested. Only three sites required more than five integration periods. The validity of EMG scanning as a diagnostic tool is enhanced by longer integration periods. |
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