Static Surface EMG: The Blood Pressure Cuff for Chiropractic Care

:dropcap_open:B:dropcap_close:lood pressure measurement has become well-accepted as a means of screening for cardiovascular health and tracking effectiveness of treatment. But the American Heart Association states clearly that test-retest reliability is poor, with variables including proper training, positioning of the patient, and selection of even cuff size impacting reproducibility.(1) Even with its questionable test-retest reliability, blood pressure measurement is considered a “gold standard” and a  required element of even the most basic physical exam.  How then is it so well accepted? Viewed in context over a long period of time, a clear pattern emerges which provides the doctor and patient with valuable clinical data in evaluating cardiovascular health and long-term treatment. 
bloodpressureStatic sEMG shares similar concerns with regards to reproducibility. Patient position, user training and proper test technique are as important with Static sEMG as with BP.  And clinical value parallels BP measures in the world of spinal health. When viewed in context over a period of time, patterns of muscular compensation clearly emerge providing valuable clinically meaningful, spinal-specific data to aid the Chiropractor and patient in determining need for care and tracking of progress. It is however crucial that one utilize proper equipment, test protocol and consider individual patient variables (e.g. height, medication, exercise) when interpreting results.  At minimum, think of Static sEMG as an electronic form of palpation.  It augments palpation by providing purely objective data which unlike palpation is quantifiable.  
Much of the criticism regarding reproducibility of Static sEMG stems from poorly designed equipment, outdated equipment, poorly maintained equipment and errors caused by improper test technique.
Clinical value has been established in several major studies. Both the Veteran’s Administration and the University of Michigan’s Spine Program have published analyses on the validity of Static sEMG, with a new paradigm regarding Static sEMG emerging.(2, 3)  Specifically, a new statistical analysis of the Static sEMG data has proven that Static sEMG can definitively track patient progress by accurately identifying patients who respond to care, and those who do not with clear statistical significance.(3) 
Interestingly, an overwhelming majority of studies finding clinical value in Static sEMG performed the test in the standing posture.  Not only is the Standing sEMG match more closely the fundamental principles of “loading” established as important by Chiropractic X-Ray, but by requiring that the patient maintain their own posture, the test becomes a biomechanical “stress test”.  The result is a magnification of compensatory muscular patterns which expose underlying spinal issues.  By sitting, the biomechanical stability provided by the chair masks these compensatory muscle patterns.
That being said, there is a trade-off between clinical relevance and reproducibility which comes with this “stress test” when standing.  Seated, the body is stabilized by the chair, providing sEMG data which is more stable and reproducible, but clinically less relevant. Essentially, if you want to see the body’s response to pain or subluxation, perform the test standing.  Lower reproducibility is inherent in stress testing, but data obtained is almost always clinically more meaningful.
One study pointed to the reality that the quality of sEMG equipment, (like all equipment) varies greatly with the resultant effect on the clinical value.  Researchers concluded that the use of more advanced sEMG equipment contributed to the statistical significance found. Prior to this study, it had always been assumed that all sEMG equipment was equally as accurate.(4)
There are a few quick and simple practical tests which can evaluate quality of any Static sEMG prior to use in the clinical setting. In addition, these tests can help determine the need for maintenance or calibration as even high quality equipment requires upkeep. 
Two Step Procedure for Evaluating Static sEMG Instrument
1.  Utilizing clean, new electrodes, and following the skin preparation procedure recommended by the manufacturer (utilize electrode prep gel/liquid if required), enter the data capture screen of your program.
Making certain to place electrodes directly on skin in an area with no hair, see if the readings drop rapidly.  Upon skin contact, readings should drop within 1-2 seconds.  If readings do not drop quickly, this gives you an indication that the device may have difficulty with electrical interference and may provide questionable data.
2.   Next, following the same process, touch the probes to the skin on the forearm flexors.  While holding the device on the forearm flexors, alternatively make a fist, hold it, and relax.  The readings on the screen should go up and down correlating with the contraction required to make a fist.  If readings do not correlate with this action, there may be an issue with the instrument.
:dropcap_open:Gathering good data can only lead to better patient care and the resultant practice growth.:quoteleft_close:
If you do not get good results with the above tests, perform the same tests a different physical location (like the home) with the computer running on battery power (if a laptop).  This can help determine if there are electrical interference issues at your office. 
Now that you have ensured that your Static sEMG equipment is working properly, apply these simple procedures below to maximize reproducibility. 

1. Always test with the shoes off. Shoe height varies (greatly in some cases) and this variable will make the readings meaningless if not taken into account.  This of course cannot be done at a screening.  
If asked about test validity at a screening, explain the limitations at a screening, and offer a free exam in your office for a more clinically valid exam. 
2. Make certain to follow proper skin preparation for each test.  Don’t expect to get the same results twice if you clean the skin with alcohol the first test, and don’t on the second.  Make sure to use manufacturer recommended conductive gel/liquid at every measurement point.  
3. Stand the patient so you can see the screen, but they cannot. Even a peripheral view of the screen will lead them to turn their head, thus throwing off the readings. 
4. For measurements done on individuals who exercise daily, or have a job involving heavy manual labor, it is important to look at the pattern of activity, and less at the amplitude of readings. In general, testing after heavy exercise is less accurate.
5. If there is any build-up of conductive gel or liquid on the device, electrodes or mounting posts, readings will be consistently high or unpredictable.  Use Isopropyl Alcohol on a paper towel to clean the device and electrode posts, making certain there is no residue left anywhere near the electrodes or electrode posts. Make sure the posts are dry prior to remounting electrodes.
6. Replace electrodes per manufacturer requirements or if you start noticing erratic readings. When doing so, make certain to clean their mounting posts as well (see #5).
7. Be aware that when testing patients who are very tall, that variability in the results will be greater due to the simple biomechanics of height.  
8. If getting consistently high readings, eliminate sources of electrical interference by unplugging all devices in the room used for testing (unplug monitors, TV’s etc.).  Ungrounded TV’s with bad power supplies cause abnormally high readings.  If using a laptop, unplug the power supply from the wall and the laptop, and test with battery power.  If still seeing high readings, test at your home, or another location altogether.  There is the possibility that your office has a bad or missing ground connection. If readings are fine at home, but high at your office, contact the management to have the wiring evaluated. Improper grounding not only causes inaccurate readings, but can affect other office equipment as well.
9. If using a TV/LCD without a grounded power plug (three prong power plug), move the patient as far away from it as practical.  Electrical interference is generated by ungrounded equipment, but moving the patient even a few feet from the screen can prevent this interference from contaminating the signal.  
A rationalization I’ve heard for using faulty equipment and/or poor test protocol is that the tool is purely to convince patients to seek care.  You are a Doctor and a professional.  As we would find it completely unacceptable for an MD to provide false blood test results to get us on medication, it is actually inappropriate to present data you know as questionable as a means of inducing patients into care.  As Chiropractors we need to have higher standards especially if we are to garner the respect of a tech savvy population growing ever more discerning.  Gathering good data can only lead to better patient care and the resultant practice growth.
Technology can be your best friend or worst enemy. By finding the best product and support for your needs, you will have a great partner in building your practice. Follow some simple guidelines, and you will enjoy all the advantages of technology without the stress. 

Dr. Nancy Miggins has over 25 year’s clinical experience as a chiropractor. She excelled in the areas of procedures, ethical business practices and management. After spearheading the development of a integrative health and fitness center, she spent 6 years as director of this clinic. Although her main focus was in family practice, she also has aided Olympic Athletes and professional cyclists with optimizing sports performance through chiropractic. She is currently the Director of Clinical Applications & Product Development for Precision Biometrics, Inc. Contact at : [email protected] or visit or call 800-969-6961

David Marcarian, MA, founder of Precision Biometrics, and inventor of the revolutionary MyoVision 3G Wirefree PhysioMonitoring™ System. A former NASA researcher, Marcarian was awarded a $450,000.00 NIH grant to develop the MyoVision.  As an expert witness, Marcarian was credited one of the largest PI awards in US history, and established the validity of sEMG in a major State Superior Court Decision. Recently the AMA selected his 3G Wirefree System as the “tool of choice” as presented in the medical text  “The Practical Guide to Range of Motion Assessment”. Contact at : [email protected] or visit or call 800-969-6961

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