Posts Tagged ‘electromyography definition’

Surface EMGs are generally performed for differing reasons than the needle EMG. Most surface EMG are performed by MD or DC ´s who are involved in the physical medicine and rehabilitation aspects of treating acute or chronic whiplash associated disorders. In addition, the surface EMG is also used in evaluation muscle contraction patterns in human volunteer studies where stimulated rear end crashed have been performed.

The surface EMG is used for several reasons:

• determine muscle contraction forces and strength

• determine if abnormal recruitment patterns of the muscles and tendons exist

• Abnormal fatigue patterns of muscles

• abnormal patterns of skeletal muscle activity

• abnormalities of muscle tone

• post surgical muscle patterns of motion

• tool of monitor improvement of motor function and rehabilitation progress

• Tool to estimate ability of person to perform a specific work activity

• tool to estimate ability of person to perform athletic activity

• tool to determine prognosis

There are several studies that evaluate the use of surface EMG relative to whiplash injuries. Studies have shown that surface EMGs have shown  anomalous  muscle animation motif of the upper trapezius muscles in the acute whiplash people. The authors evaluated 92 acute whiplash patients for muscular activation patterns to determine if similar patterns were exhibited in the acute patient. The study concluded that acute whiplash patients exhibited reorganization of the muscles in the neck and shoulder muscles. Elert compared surface EMG findings in 59 patients with chronic whiplash disorders and fibromyalgia to a control group finding that the control group had higher dynamic output than the whiplash fibromyalgia group. Falla in a study of chronic neck pain patients and a control group, concluded that when using surface EMGs, the chronic neck patients had a delay in muscle activity when flexing and extending their arms. This delay in neck pain patients was due to a significant deficit in the automatic control of the deep cervical spine muscles.

Other authors use the surface EMG to evaluate the outcome of cervical radiculopathy surgery. Lofgren evaluated 27 patients who had anterior or posterior cervical spine surgery for  radiculopathy. Pre and post surgical muscle strength and trapezius muscle microcirculation were both evaluated.

The tester needs to recognize that the EMG Test signal may be attenuated by the depth of the subcutaneous fat tissue layer, depending upon the distance between the electrode and the muscle that is being tested. Norlander recommends that the singnal be normalized for each invidividual.

Elecromyographic bio feed back in rehabilitation is now standard procedure. With respect to diagnosis, there are also promising results in the use of the surface EMG signal to classify muscle impairments in persons with lower back pain. These techniques are based on the phenomenon of the compression of the power spectral density spectrum of the EMG signal towards lower frequencies during sustained contractions and the fact that is change is associated with the metabolic concomitants of muscle fatigue. Using the various methods in which EMG median frequency limit alter change as an aftermath of contraction duration and muscle site as well as the symmetry of activation during the early part of the contraction, these investigations have shown the surface EMG signal to perform significantly better than conventional clinical parameters at correctly classifying patients with and without lower back pain.