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Surface deception – surface EMG

Home/Research/Surface deception – surface EMG

by Dr. Stephen M. Perle
from his blog Perles of Wisdom

Although the article that stimulated this blog was published in February, I was only alerted to it by an automated Google news search, whose results that were emailed to me this week. The article is about the use of surface EMG to diagnose chiropractic subluxations. I won’t go into the validity of the concept of the subluxation as I have co-authored a paper on that already, and the literature that supports or refutes our paper has not changed in any substantive way that I know of.

The article, sEMG: An overview, in my opinion, does little more than express, what I think, is a biased belief lacking any evidence that a subluxation can be demonstrated by sEMG. sEMG or surface EMG is a useful tool for certain purposes. One of those purposes doesn’t happen to be diagnosis. It is really a research tool. Used to determine which muscle is active during certain movements. There are some sophisticated methods that are showing some promise in determining dysfunction that may be at the root of low back pain (1) or validating the diagnosis of low back pain. (2) but nothing I have seen suggesting that the sEMG can help find a subluxation. (3)

One fundamental problem with the use of sEMG to diagnose subluxations is that none of the methods used by my colleagues at this time involve what is called normalization. Normalization is where one converts the electricity measured during the sEMG to percent of maximum volitional movement or percent of some predetermined activity. The reason normalization is important is if one is just trying to compare the voltage from one patient to set of “normal” values inside the device one does not account for variables that change that voltage independent of muscle activity. For example, if one has an obese patient and thin one, the obese patient will have lower voltage readings on the EMG because fat is a great insulator without regard to the actual activity of the muscle. (4, 5) None of the sEMG devices that are marketed to chiropractors require normalization procedures before they produce their pretty computer graphics supposedly showing where the subluxation is.

Now most doctors of any profession lack the training that would provide them with the knowledge to evaluate the claims of the sEMG manufactures. However, if one reads the sEMG: An overview there are to simple clues to the lack of validity of these devices. The only references used are a twenty-two year old pilot study and a twenty year old book. Given the fact that approximately ten thousand papers are published weekly in the biomedical literature it is not that common that one needs to rely on such old references. Especially when professional groups both outside (6) and inside the chiropractic profession (7) have published since then noting the lack of validity of the use of these devices.(6, 7)


1. Cholewicki J, Silfies SP, Shah RA, Greene HS, Reeves NP, Alvi K, et al. Delayed trunk muscle reflex responses increase the risk of low back injuries. Spine. 2005 Dec 1;30(23):2614-20.
2. Geisser ME, Ranavaya M, Haig AJ, Roth RS, Zucker R, Ambroz C, et al. A meta-analytic review of surface electromyography among persons with low back pain and normal, healthy controls. J Pain. 2005 Nov;6(11):711-26.
3. Owens EF, Jr. Chiropractic subluxation assessment: what the research tells us. J Can Chiropr Assn. 2002;46(2):215-20.
4. Lehman GJ, McGill SM. The importance of normalization in the interpretation of surface electromyography: a proof of principle. J Manipulative Physiol Ther. 1999;22(7):444-6.
5. Ng JK, Kippers V, Parnianpour M, Richardson CA. EMG activity normalization for trunk muscles in subjects with and without back pain. Med Sci Sports Exerc. 2002 Jul;34(7):1082-6.
6. Pullman SL, Goodin DS, Marquinez AI, Tabbal S, Rubin M. Clinical utility of surface EMG: report of the therapeutics and technology assessment subcommittee of the American Academy of Neurology. Neurology. 2000 Jul 25;55(2):171-7.
7. Position Statement of the American College of Chiropractic Consultants on sEMG 2006

About the Author:

Dr Wiens created the very first chiropractic information page on the web in Nov 1994. In 1995 he joined as chief designer. He lives in Canada.


  1. Chris Drotar D.C. July 11, 2009 at 10:48 am

    Sorry, but I have to disagree with your premise.

    You are rejecting SEMG on the basis that it cannot “find” a subluxation. So what? NO ONE FINDING by itself defines a subluxation. The real question is: “Can it find muscle imbalance?”. And the answer is: “Yes. Of course”. Does it diagnose the cause of it? No, of course not, but that is not the point. It is a single data point, not a substitute for clinical judgement.

    I don’t know your definition of a subluxation but if it includes any sort of “dysfunction” you should be interested in methods to objectively measure the various aspects of that dysfunction.

    Personally if I know that a patient has a spike in muscle activity in a particular area you can bet your bottom dollar I will want to know why. I will use history, inspection, palpation, x-ray etc and yes, SEMG (if available) until the issue is reasonably settled.

    There is nothing new in this. Over the years I have also heard similar arguments against thermography, palpation, x-ray analysis, you name it someone has “proven” that it does not “find” a subluxation. Big deal. If it did, you would not be necessary.

    Your call I guess.

    Chris Drotar D.C.

  2. Stephen M. Perle, DC, MS July 14, 2009 at 7:21 am

    Unfortunately, the way sEMG is performed in most chiropractors’ offices no it can’t find a “muscle imbalance”. Without normalization one cannot ascertain that the differences from side to side are real or just differences in placement of the electrodes, pressure on the electrodes or other parameters unrelated to the actual muscle activity. Further “muscle imbalance” might be the norm for the patient as most people do not do ADLs with perfect symmetry.

    Don’t you mean clinical bias rather than clinical judgment?

    My definition of subluxation? See:
    Subluxation: dogma or science?

    And you are right there was nothing new in this. We have no valid or reliable ways to find THE subluxation. That is why the author of the article in Chiro Eco used ancient references. When the current literature doesn’t support your belief system the best way to avoid the harsh realities that should cause one to change is to cite old, poorly done research. It is the refuge of those who who want to HAVE been right not to BE right.

    “The desire to be right and the desire to have been right are two desires, and the sooner we separate them the better off we are. The desire to be right is the thirst for truth. On all accounts, both practical and theoretical, there is nothing but good to be said for it. The desire to have been right, on the other hand, is the pride that goeth before a fall. It stands in the way of our seeing we were wrong, and thus blocks the progress of our knowledge.”

    W.V. Quine and J. S. Ullian, The Web of Belief (Random House, New York, 2nd edition, 1978), p. 133

  3. Chris Drotar D.C. July 14, 2009 at 9:58 am

    Operator error, lack of insight, poor training (electrode placement, tissue thickness etc) are all hazards of ANY procedure and is not inherent in SEMG per se.

    I do not reject carpentry because some people do not know how to drive a nail.

    I am not sure what you mean about my “clinical bias”. Frankly I try not to read ineptitude into the other person, no matter how much they may beg for it.

    Chris Drotar D.C.

  4. Stephen M. Perle, DC, MS July 14, 2009 at 12:57 pm

    Yes but one does not use a nail to put in a bolt. Using sEMG, as marketed to DCs, is worse it is akin to using a hammer to wire a computer. One does not use sEMG to do side to side comparisons and expect to have valid results unless one has used normalization procedures which these systems don’t use. Of course one could discount all sources of error, which completely invalidate the device for this use IF one has enough belief in chiropractic and the subluxation. 🙂

    Show me the evidence that these produce valid and reliable results from those who aren’t inept and I’ll change my tune until then lets call the spade a spade. They are simply wiz bang computerized systems used to manipulate, in a Machiavellian way, unsuspecting doctors and their patients into believing that the patient needs continued adjusting regardless of the ability of the technician.

    Using valid and reliable outcome measures is the path to patient centered and not doctor centered care.

  5. Obie Bendix July 14, 2009 at 12:59 pm

    Which of the following scenarios do you think is closer to the truth?

    1. We use sEMG because it provides unique clinical information which helps to formulate a treatment plan and enhances patient outcome. We couldn’t do without it.

    2. We use sEMG because it looks like modern technology and provides pretty pictures which enhances patient retention and referral. We couldn’t do without it.

  6. Stephen M. Perle, DC, MS July 14, 2009 at 1:23 pm

    I think that most DCs that use sEMG do so because they believe #1. Call this moral self-deception.

    However, there is no evidence that the sEMG does anything to enhance patient outcome. It seems that it is only effective at increasing patient dependence upon their doctor.

    One sEMG company used to have on their web site, with pride, that those who use their sEMG increase the patient visit average X number of visits. Maybe I’m stupid but I think helping a patient get well in less visits is an enhanced patient outcome. But clearly getting a patient to come more often does enhance the patient’s potential for generating income for the doctor.

    Patient retention is not necessarily a good thing, in fact, our goal in practice should be teaching patients how to be independent of us. Doctor-dependency is a problem for all health professions. Want real wellness/preventive care – teach people to exercise, eat well, stop smoking, wear seatbelts and that doesn’t take an sEMG to do.

    So my answer is #3

    #3 You use sEMG because you believe it provides unique clinical information which you believe helps to formulate a treatment plan and you believe enhances patient outcome but in reality you use sEMG because it looks like modern technology and provides pretty pictures which enhances patient retention and referral. You couldn’t do without it because it enhances your income.

  7. Chris Drotar D.C. July 14, 2009 at 9:43 pm

    I am sorry, but I think you are finally getting on my nerves.

    I suggest you stop lecturing us about our supposed attitudes /motives and pony up some real facts if you have them.

    I have never once intimated that SEMG did anything but help localize areas of altered muscle activity. The doctor decides what that does or does not mean. (Do I really have to explain this?)

    If you object to what you consider to be exaggerated claims from the manufacurer, then take it up with the sate board.

    Surface EMG and thermography are two technologies that have held great promise for our profession, despite thier limitations.

    I have for a good many years watched our “learned” colleges gin up self serving crediblity by trashing our attempts to develop these tools. If I could characterize anything as “Machiavelian” that would have to be it.

    lastly, if you really want to impress someone I suggest you do some clincal research and publish protocols which you feel would insure productive and ethical advancement of these tools. I will be the first to sing you praises.

    Otherwise, the rest of us know how the cow ate the cabbage. You are only kidding yourself if you think otherwise.

    Chris Drotar D.C.

  8. Stephen M. Perle, DC, MS July 14, 2009 at 10:21 pm

    You want real facts. The problem is that you don’t like them and they aren’t consistent with your beliefs.

    There is no evidence that I am aware of that the information one get from the sEMG equipment being marketed to chiropractors is of any value. The fact that you ascribe value to it, does not make it valuable.

    In my initial blog posting which was reproduced above I gave the references for what I have asserted about the sEMG.

    You have made a positive assertion about the clinical utility of the device. Thus, the onus is on you “pony up some real facts.” That is you need to provide the evidence that the equipment you have is capable, in a valid and reliable way, to determine the altered muscle activity (whatever THAT is). THEN if you can do that, the onus is on you to provide the evidence that altered muscle activity is clinically meaningful.

    You are correct sEMG and thermography do hold promise. But until the research shows what clinically important information they provide us, they are little more than research tools that have been pushed upon chiropractors with all manner of pie in the sky promises – even the promise that it will let you know about muscle activity.

    I’m sure that if MRI’s were cheaper there would be someone trying to sell our profession on them as a subluxation detector or something else.

    Fortunately, I have no particular need or desire to impress you. As long as my wife and kids love me and respect me I’ll have impressed everyone that’s important to me. I’ve already impressed enough faculty and administrators at UB to have earned tenure and promotion to associate professor and then to full professor. I’m done trying to impress. But I’ll continue to do the research that interests me on the biomechanics of manipulation and investigating quality of chiropractic care.

    You suggest that I should do research that would insure productive and ethical advancement of these tools. IF I did that kind of research no one with any training in research would accept the results as that is a biased approach. IF they interested me, then I’d do research to test if they were clinically useful – which as I said there is no research that I am aware of showing such.

    If you are really interested in what clinical research on sEMG has found I can recommend various papers. One of the most interesting lines of research I have seen is the work of Jacek Cholewicki, PhD. Here are some papers that might interest you.

    1. Radebold A, Cholewicki J, Panjabi MM, Patel TC. Muscle response pattern to sudden trunk loading in healthy individuals and in patients with chronic low back pain. Spine. 2000 Apr 15;25(8):947-54.
    2. McGill SM, Cholewicki J. Biomechanical basis for stability: an explanation to enhance clinical utility. J Orthop Sports Phys Ther. 2001;31(2):96-100.
    3. Radebold A, Cholewicki J, Polzhofer GK, Greene HS. Impaired postural control of the lumbar spine is associated with delayed muscle response times in patients with chronic idiopathic low back pain. Spine. 2001 Apr 1;26(7):724-30.
    4. van Dieen JH, Cholewicki J, Radebold A. Trunk muscle recruitment patterns in patients with low back pain enhance the stability of the lumbar spine. Spine. 2003 Apr 15;28(8):834-41.
    5. Cholewicki J, Silfies SP, Shah RA, Greene HS, Reeves NP, Alvi K, et al. Delayed trunk muscle reflex responses increase the risk of low back injuries. Spine. 2005 Dec 1;30(23):2614-20.
    6. Hodges P, van den Hoorn W, Dawson A, Cholewicki J. Changes in the mechanical properties of the trunk in low back pain may be associated with recurrence. J Biomech. 2009 Jan 5;42(1):61-6.

    If anyone is interested I can provide other references to promising research with sEMG.

    The how the cow ate the cabbage? That’s Greek to me. I thought they eat grass 🙂

  9. Chris Drotar D.C. July 15, 2009 at 7:40 am

    Excuse me, but you just referenced several research studies about muscle loading, etc etc. I have 3 questions for you:

    1.) What instrumentation did they use to study muscle recruitment?

    2.) If it was SEMG and as you say SEMG has no value in measuring muscle function does that not make your own citations invalid by your criterion?

    3.) On the other hand, if these studies do rely on SEMG, and if they are valid and reliable as you say they are, does that not prove my point?

    By the way, (without going into too much history) the saying “How the cow ate the cabbage” is a Texas expression. As I understand it, it means to “tell it the way it happened” the down and dirty detail so to speak. It the context of my post it means that the average practicioner knows what has been done to them, and by whom.

  10. Stephen M. Perle, DC, MS July 15, 2009 at 11:10 pm

    1. Cholwicki used a standard 12 channel EMG (I’ve seen it and believe it was just an op amp system with A/D conversion into a PC) where a raw signal is processed by the researcher. I can’t violate copyright and reproduce the methods here. For details I suggest getting the paper or these two papers where preliminary research testing this data acquisition method.

    Cholewicki J, McGill SM. Mechanical stability of the in vivo lumbar spine:
    Implications for injury and chronic low back pain. Clin Biomech 1996;11:1–15.
    Cholewicki J, Panjabi MM, Khachatryan A. Stabilizing function of trunk
    flexor/extensor muscles around a neutral spine posture. Spine 1997;22:2207–12.

    I have not seen a single system marketed to chiropractors that does this. I use a Noraxon telemetered 6 channel EMG in my lab. We’ve not done any research with it in a while because the neurophysiologist who initially did the work with on this has since left the College of Chiropractic. He couldn’t keep up with the 2.5 hour commute.

    2. I believe I was careful in saying that the problem with sEMG are the systems sold to chiropractors have no value in measuring muscle function not that sEMG by itself is not valuable.

    3. So no it does not prove your point unless the sEMG system you use is the same and you use the same protocol for data collection and data analysis that Cholewicki has shown to be valid.

    For example the fact that NASA can measure the distance to the moon by reflection of a laser off a target left by an Apollo mission to fractions of a millimeter doesn’t mean you can do that at home with your pocket laser pointer.

    AND Cholewicki’s research has shown that the time that it takes for a muscle to turn on in a controlled situation in these experiments can be used to predict who will get back pain. Right now there is no practical clinical implication but time will tell.

    I notice that you haven’t provided me with any references for your “facts”.

    After 6 years of living in TX I had never heard that idiom.

  11. Chris Drotar D.C. July 17, 2009 at 8:48 am

    The last refuge of the scoundrel. Barricaded behind his best cherry-picked anecdotes.

    So let’s see, you are betting that there are no studies validating 2 channel EMG. Think I’ll call you bluff on that one.

    I suspect that this time my next post will be more of an embarrassment to a certain academic that cannot be bothered to do SEMG studies without his “physiologist” handy, but belittles practicing doctors that use a simplified method.

    Oh and by the way, In over a dozen years in Texas I heard the term plenty of times. Maybe we just travel in different circles.

    All the best.
    Chris Drotar D.C.

  12. James W. Lovett July 17, 2009 at 12:36 pm

    I have read both of your arguments and the point that really needs to be brought up is that SEMG is just a tool, it does not delineate subluxations. More importantly, it does not indicate the effectiveness of the doctors skill initially. However, after 10-15 visits I myself would be looking for a different doctor because the one you have might not have adjusting skills, clinical knowledge of what else might be going on in the body that is limiting the body to heal itself. It could be biochemical, emotional(spiritual) or other structural fault that they missed.

  13. Obie Bendix July 17, 2009 at 3:49 pm


    You are typical of the chiropractor who refuses to be swayed by the facts. When presented with cogent opinions he feels he’s being attacked personally and starts resorting to ad hominem arguments while at the same time refusing to provide any evidence of his own.

    If you have no evidence you wish to present aside from personal opinion, it’s time to stop eating cabbage and start eating crow.

  14. Chris Drotar D.C. July 17, 2009 at 4:12 pm

    Hey Obie, if you read my last post, you should have figured out that that is exactly what I intend to do.

    I wanted to avoid it, as I thought it would just be an unecessary embarrassment to Dr. Perle. Unfortuantely he seems to insist that I do just that.

    However if I am to bo goaded into this project, I will take a little time and do it right.

    Thank you for your kind thoughts.

    Chris Drotar D.C.

  15. Stephen M. Perle, DC, MS July 17, 2009 at 11:19 pm

    I believe that I have presented the research that I am aware of on the topic to support my argument. I do not believe I have resorted to anecdote, that Dr. Drotar seems to be your forte. My evidence for this is that as yet I have not found in your responses a single reference, ergo your argument is bereft of supportive evidence and is right now little more than opinion and anecdote.

    Given that I have stated that I am presenting my opinion, informed by the references I presented, that this is what I am aware of AND that I have asked twice for your references (call this a third attempt), I fail to see how informing me of the literature, which again I have stated that I am unaware of, would be embarrassing.

    Once again I provide this quote.

    “The desire to be right and the desire to have been right are two desires, and the sooner we separate them the better off we are. The desire to be right is the thirst for truth. On all accounts, both practical and theoretical, there is nothing but good to be said for it. The desire to have been right, on the other hand, is the pride that goeth before a fall. It stands in the way of our seeing we were wrong, and thus blocks the progress of our knowledge.”

    W.V. Quine and J. S. Ullian, The Web of Belief (Random House, New York, 2nd edition, 1978), p. 133

    This applies to me too. I have no problem with being wrong in the past and will change my opinion provided with the appropriate evidence that I ought to change.

    If, however, it makes you feel better to believe that providing references for the, as yet unsubstantiated facts you present, would embarrass me, then I’ll feign embarrassment for you.

  16. Chris Drotar D.C. July 18, 2009 at 12:54 pm


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