Even though most people are aware of the effects of gross muscle activity, lower chronic levels of activity often produce no visible movement or perceptible sensation and as a result go unnoticed, often resulting in muscle fatigue and pain.
Up until recently, input characteristics of EMG amplifiers and electrodes required considerable preparation of the skin surface and electrodes to obtain an accurate signal, especially in electrically noisy environments. This effort may still be worthwhile if research is being performed, but for day to day use of EMG, the preparation is cumbersome, generally inconvenient and often painful. I will discuss the recent breakthrough in EMG instrumentation later, but first I would like to review several of the newer applications for which EMG monitoring is being applied.
One of these fields is biofeedback. Biofeedback is simply the process of monitoring any physiological signal, and amplifying, conditioning, and displaying it to the monitored subject so that he or she can observe small changes in the signal, and gradually through trial and error, learn to control it voluntarily.
The goal of EMG biofeedback is to train subjects to increase, decrease, or stabilize muscle tension. Feedback is provided through proportional changes in a moving meter, bargraph, polygraph display, or an auditory tone. Training patients to decrease EMG activity below a predetermined criterion, is used clinically for tension headaches and other muscle pain. A similiar process in reverse is employed during muscle rehabilitation, where patients are trained to increase muscle activity of weak or flaccid limbs, such as may result from a stroke or accident.
For over 40 years, the electromyograph has been used to diagnose and treat neuromuscular disorders and to demonstrate improvements in muscle functioning following conventional treatment or neuromuscular stimulation. However, it is only since the mid 1960's, and much more so in the last twenty years, that biofeedback has become an active component in the rehabilitation process.
Voluntary control of paralyzed or damaged muscles with residual functioning - such as results from stroke and nerve damage - can often be achieved through EMG biofeedback using either subdermal needle electrodes or surface electrodes for monitoring individual muscle groups. The process of surface monitoring is straight-forward. The body of the disabled muscle is identified, electrodes are placed over the length of the muscle and the subject is provided with visual and auditory feedback of increases in muscle activity while instructed to try to raise the tone or meter reading. Occasionally, a neuromuscular stimulator is combined with the EMG, such that when muscle activity exceeds a pre-set threshold, the stimulator is triggered, modelling a contraction. The threshold level is then increased slightly, and the process is repeated.
The greatest use of neuromuscular biofeedback has been in patients with hemiplegia and paraplegia. Paraplegia is usually due to spinal cord injuries resulting in paralysis below the waist, whereas hemiplegia is generally caused by a stroke resulting in muscular flaccidity or paralysis on one side of the body. Yet, most therapists working with these patients can attest that frequently there is some residual muscle activity in the single motor units, or even in totally paralyzed residual muscle tissue. Sensitive EMG devices can detect this low activity, and provide awareness and often a greater degree of control over the afflicted muscles.
In many reports with hemiplegic patients, following a combination of manual range of motion activity initiated by the therapist, with visual and auditory feedback of muscle activity, patients were able to produce strong voluntary contractions within one hour of training. Even in patients who had failed to respond to long term conventional treatment, clinically significant improvements were achieved over 8 to 12 months of auditory EMG training.
Reports of successful applications of EMG biofeedback in patients with injury or impairment of peripheral nerves rather than some central nervous system dysfunction include Bell's Palsy (a facial paralysis of unknown origin), and crushing injuries. In several patients with Bell's palsy, residual muscle activity was detected from muscles surrounding the mouth. Patients were successfully trained to increase the electrical activity, as well as to try to match the activity from the contralateral muscles displayed on a second EMG display.
EMG biofeedback has also been used successfully to retrain muscular control following accidental lacerations and subsequent surgical repair of hand tendons. Combined with conventional physiotherapy, the patients provided with biofeedback made the greatest improvements in voluntary range of motion activity.
Spasmodic torticollis, also known as wryneck, is indicated by the pulling of the neck to one side due to neck muscle contractions of unknown etiology. Treatment included EMG biofeedback affected sterno-cleido-mastoid muscle activity alone, or combined with contralateral flexion. Approximately 40% of the patients receiving this feedback were markedly improved at a 6 months follow-up.
Several other neuromuscular disorders have responded well to EMG biofeedback. Some of these include: training facial expressions to blind persons by providing auditory feedback of appropriate increases and decreases in muscle patterning; decreasing blepharospasm (involuntary eye blinking) activity; and training to enhance retention in fecal and urinary incontinence, both with vaginal and rectal electrode sensors, as well as with peri-anal electrodes.
In summary, the use of EMG biofeedback in neuromuscular rehabilitation, has demonstrated considerable effectiveness in a wide variety of neuromuscular disorders, and should certainly be considered as an inexpensive and positive adjunct to conventional therapy.
EMG biofeedback has also been used very successfully to produce voluntary reductions in muscles exhibiting excessive muscle activity for general relaxation, and specifically for conditions including tension and migraine headaches, insomnia, hypertension, and pain.
In disorders involving musculature in the region above the shoulders, generally the goal is to keep muscle activity at a 'normal' resting level, and to help patients learn to both perceive increases in muscle activity during the day, and to develop a strategy to reduce tension before it leads to ischemic muscles and pain. Similarly, chronic pain sites often respond well to decreased EMG activity, providing - in many cases - some relief from pain.
Dental applications include TMJ (temporomandibular joint pain and dysfunctions) and bruxism, which are dysfunctional clenching and grinding of the teeth which often leads to TMJ pain as well as tooth damage. EMG treatment for TMJ pain and bruxism uses EMG monitoring of the TMJ region, both to provide feedback for diurnal use to keep activity below a threshold level as well as to correlate the occurrence of excess activity with stress, and for nocturnal use, to set a threshold, above which an alarm will sound, awakening the patient and aborting the bruxing episode.
Recently, another application of EMG monitoring has become popular with chiropractors, orthopaedic specialists, and physiotherapists - muscle imbalances. The most frequent use of this new technology is to document these imbalances in a dynamic fashion, to register changes due to therapeutic interventions, and to exhibit them to patients and insurance carriers. This is done by using two EMG sensors placed on either side of the spine, while the instrumentation compares readings as the two sensors are moved from site to site down the spine.
Until the mid 80's, the process of muscle scanning was difficult and slow, due to the requirements for skin preparation, attachment of the electrodes, and interpretation of the instruments. There are now several excellent instruments available which eliminate these shortcomings, in several ways. For example, MyoTrac and MyoTrac 22 use a miniature scanning sensor - MyoScan - with internal electronics which are so sensitive and advanced that generally no skin preparation is required, thereby allowing a site to be scanned within seconds. For those of you interested in specifications, the system has a d.c input impedance of greater than 1 million megohm (that's a million, million ohms), the ability to detect signals of less than .08uV, and a CMRR of greater than 180 decibels, thereby allowing signal detection even in extremely electrically noisy environments.
The MyoTrac 2 can also be connected to interfaces which simply plugs into the serial port on IBM-PC compatibles providing immediate access to powerful ProComp software.
Other more sophisticated computerized biofeedback systems are available such as ProComp+TM and FlexCompTM which monitors up to 16 channels of EMG or other signals. Powerful and flexible DOS and Windows® software is available to provide clinicians and patients with meaningful and compelling displays, animations and statistics.
An electromyogram (EMG) measures the electrical impulses of muscles at rest and during contraction. Nerve conduction studies, which measure nerve conduction velocity, determine how well individual nerves can transmit electrical signals. Nerves control the muscles in the body using electrical impulses, and these impulses make the muscles react in specific ways. Nerve and muscle disorders cause the muscles to react in abnormal ways.
Measuring the electrical activity in muscles and nerves can help detect the presence, location, and extent of diseases that can damage muscle tissue (such as muscular dystrophy) or nerves (such as amyotrophic lateral sclerosis). In the case of nerve injury, the actual site of nerve damage can often be located. EMG and nerve conduction studies are usually done together to provide more complete information.
An electromyogram (EMG) is done to:
Nerve conduction studies are done to:
Both EMG and nerve conduction studies can help diagnose a condition called post-polio syndrome that may develop months to years after a person has had polio.
Tell your doctor if you:
You do not need to restrict your food or fluids. Do not smoke for at least 3 hours before the test.
Wear loose-fitting clothing that permits access to the muscles and nerves to be tested. You may be given a hospital gown to wear.
For an EMG, you may be asked to sign a consent form. Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information formAn electromyogram (EMG) is done in a hospital, clinic, or doctor's office. A special room that screens out electrical interference may sometimes be used. The test may be performed by an EMG technologist or a doctor specializing in diseases of the nervous system (neurologist) or in physical rehabilitation (physiatrist).
You will be asked to lie on a table or bed or sit in a reclining chair so that the muscles being tested are relaxed and easy to reach.
The skin over the areas to be tested is cleaned with an antiseptic solution. An electrode that combines the reference point and a needle for recording is inserted into the specific muscle to be tested and attached by wires to a recording machine.
Once the electrodes are in place, the electrical activity in that muscle is recorded while the muscle is at rest. Then the technologist or doctor asks you to tense (contract) the muscle with gradually increasing force while the electrical activity in the muscle is being recorded.
The needle may be repositioned a number of times to record the electrical activity in different areas of the muscle or in different muscles.
The electrical activity in the muscle is displayed as wavy and spiky lines on a special video monitor (oscilloscope) and may also be heard on a loudspeaker as machine gun-like popping sounds when you contract the muscle. The activity may also be recorded on magnetic tape.
An EMG may take 30 to 60 minutes. When the testing is completed, the needle and skin electrodes are removed and those areas of the skin where a needle was inserted are cleaned. You may be given a pain reliever if any of the areas where a needle was inserted are sore.
In this test, several flat metal disc electrodes are attached to your skin with tape or a special paste. A shock-emitting electrode is placed directly over the nerve to be studied, and a recording electrode is placed over the muscles supplied by that nerve. Repeated, brief electrical pulses are administered to the nerve, and the time it takes for the muscle to contract in response to the electrical pulse is recorded. The speed of the response is called the conduction velocity.
The corresponding nerves on the other side of the body may be studied for comparison. When the testing is completed, the electrodes are removed.
Nerve conduction studies are usually done before an EMG if both tests are being done. Nerve conduction testing may take from 15 minutes to 1 hour or more, depending upon how many areas of the body are studied.
With an electromyogram (EMG) test, you will feel a brief, sharp pain each time a needle electrode is inserted into the muscle. Some people find this part of the test very uncomfortable. After EMG testing, some soreness and a tingling sensation may persist for 1 to 2 days. If you notice increasing pain, swelling, tenderness, or pus at any of the needle insertion sites, call your doctor.
With the nerve conduction studies, you will feel a brief, burning pain, a tingling sensation, and a twitching of the muscle each time the electrical pulse is applied. It feels similar to the kind of tingling you feel when you rub your feet on the carpet and then touch a metal object. The testing can be quite uncomfortable and makes some people nervous. Keep in mind that only a very low-voltage electrical current is used, and each electrical pulse is very brief (less than a millisecond).
An electromyogram (EMG) is very safe. You may develop small bruises or swelling at some of the needle insertion sites. The needles are sterilized, so there is very little chance of developing an infection.
There are no risks associated with nerve conduction studies. Nothing is inserted into the skin, so there is no risk of infection. The voltage of electrical pulses is not high enough to cause an injury or permanent damage.
An electromyogram (EMG) measures the electrical impulses of muscles at rest and during contraction. Nerve conduction studies, which measure nerve conduction velocity, determine how well individual nerves can transmit electrical signals. Your doctor may be able to discuss some findings with you immediately after the tests. A full analysis of the results may take a few days.
Normal: | The EMG recording should show no electrical activity when the muscle is at rest. There should be smooth, wavelike forms with each muscle contraction. |
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The nerve conduction studies should show that the nerves transmit electrical impulses to the muscles or up the sensory nerves at normal speeds (conduction velocities). Sensory nerves allow the brain to respond to sensations such as pain, touch, temperature, and vibration. Different nerves have different normal conduction velocities. Nerve conduction velocities also tend to decrease as a person gets older. | |
Abnormal: | In an EMG, spontaneous electrical activity detected in a muscle at rest suggests that there is a problem with the nerve supply to the muscle. This kind of activity can also be caused by inflammation or disease in the muscle tissue. Abnormal levels and duration of electrical discharges when a muscle contracts also suggest the presence of a muscle or nerve disorder, such as amyotrophic lateral sclerosis (ALS), post-polio syndrome, or a herniated disc. |
In nerve conduction studies, the speed of nerve impulse transmission (conduction velocity) may be slower or faster than what is normal for that nerve. Slower conduction velocities may be caused by injury or may damage a nerve (such as carpal tunnel syndrome) or group of nerves (such as Guillain-Barré syndrome or post-polio syndrome). |
The results from EMG and nerve conduction studies are usually not enough on their own to diagnose a condition. They can be used along with a person's history, symptoms, physical and neurological examinations, and the results of other tests to help establish a diagnosis and evaluate how a disease is progressing.
Factors that can interfere with your test and the accuracy of the results include:
Kinesiology encompasses human anatomy, physiology, biomechanics, exercise physiology, exercise psychology and sociology, history, and philosophy of sport. The relationship between the quality of movement and overall human health is also studied.
Kinesiological information is applied in such fields as physical therapy, occupational therapy, chiropractic, osteopathy, kinesiotherapy, massage therapy, ergonomics, physical education and athletic coaching. The approach of these applications can be therapeutic, preventive, or high-performance. The application of kinesiology can also incorporate knowledge from other academic disciplines such as psychology, physiology, sociology, cultural studies, ecology, evolutionary biology, and anthropology. Related interdisciplinary fields in motor skills, skills research are graphonomics, i.e. the study of handwriting movement control and the study of motor control in speech.
The study of kinesiology is often part of the curriculum for some of the areas in which kinesiological information is used (akin to a medical study – see sports medicine). Despite being a scientifically valid discipline, there is a perception that Kinesiology is an academically anemic major designed for athletes.
There are some professional physical therapists who are also fully credentialed as "Registered Kinesiologists." The general difference between the job of a kinesiologist and a physical therapist is that a kinesiologist will assess movement, or problems in movement with regard to physiology, anatomy and biomechanics, while a physical therapist will actually assess and apply therapeutic techniques to correct the identified problems.
Below is a (slightly simplified) table of the motions available at the different joints of the body:
Electromyography is a test that measures muscle response to nervous stimulation (electrical activity within muscle fibers).
EMG is most often used when people have symptoms of weakness and examination shows impaired muscle strength. It can help to differentiate primary muscle conditions from muscle weakness caused by neurologic disorders.
EMG can be used to differentiate between true weakness and reduced use due to pain or lack of motivation.
For an EMG, a needle electrode is inserted through the skin into the muscle. The electrical activity detected by this electrode is displayed on an oscilloscope (and may be displayed audibly through a speaker).
Because skeletal muscles are isolated and often large units, each electrode gives only an average picture of the activity of the selected muscle. Several electrodes may need to be placed at various locations to obtain an accurate study.
After placement of the electrode(s), you may be asked to contract the muscle (for example, by bending your arm). The presence, size, and shape of the wave form -- the action potential -- produced on the oscilloscope provide information about the ability of the muscle to respond when the nerves are stimulated.
Each muscle fiber that contracts will produce an action potential, and the size of the muscle fiber affects the rate (frequency) and size (amplitude) of the action potentials.
A nerve conduction velocity test is often done at the same time as an EMG.
Adults:
No special preparation is usually necessary.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
Applied Kinesiology (AK) is a controversial method of medical diagnosis. It purportedly gives feedback on the functional status of the body. Proponents say that when properly applied, the outcome of an AK test, such as a muscle strength test, will provide for a low risk diagnostic method to help determine the efficacy of therapy for patients.
Applied Kinesiology is classified with alternative medicine, and is therefore different from academic kinesiology, which is the scientific study of human movement and its application. Applied kinesiology has been called a pseudoscience. [1]
AK draws together many similar therapies. It attempts an integrated, interdisciplinary approach to health care. George J. Goodheart, D.C., a chiropractor, originated AK in 1964. [2] Subsequently, its use spread to other chiropractors, naturopaths, and a few medical doctors. In 1976, the International College of Applied Kinesiology [3] was founded.
AK practitioners monitor muscles to determine if stress is 'on line'. It is not about 'testing' the muscle in a proper sense, the important thing is the ability of the muscle (more precise: the ability of the autonomous nervous system) to respond in an appropriate way to the gentle pressure. AK patients have their muscles tested in many different functional positions, although the arm-pull-down test is the most common. Typically during the arm-pull-down test, AK patients lie down and raise their dominant arm. Next, the AK practitioner instructs the patient to resist as the tester exerts downward force on the subject's arm. The tester subjectively evaluates not the force exerted by the subject to determine the strength of the muscle, but the smoothness of the response. A smooth response is sometimes called 'a strong muscle' and a response that was not appropriate is sometimes called 'a weak response'. Please note: this is a figure of speech and not about muscle strength.
Because nearly all AK tests are subjective, many regard the practice with skepticism. The AK practitioner applies the pressure, but this practitioner is also the one who decides if one push is stronger than another. This is considered by some a conflict of interest: the AK practitioner will benefit if AK is perceived by the client as effective, but the AK practitioner is the one who actually determines how effective the practice has been, because he or she subjectively applies pressure to the patient's muscle or muscles. This weakness in the AK system allows for the possibility of fraudulent practice.
The arm-pull-down test is considered by the International College of Applied Kinesiology (I.C.A.K.) to be a very poor form of muscle testing. The arm-pull-down test involves so many different muscles that no specificity as to the muscle with the problem can be ascertained upon testing. Those who wish to become applied kinesiologists, are strongly advised and encouraged to take the 'touch for health' courses, in which the specific muscles and the precise positions for each muscle are explicitely taught.
Applied kinesiologists theorize that physical, chemical, and mental imbalances are associated with a lack of smoothness in the muscle response. So after a mucle that shows a 'weak' response (i.e. a non-appropriate response) many ways are open to find a way to restore the balance - for an imbalance is theorized to be responsible for a 'weak' response. After some form of treatment/ restoring balance has been applied, the muscle is again monitored, to evaluate the efficiacy of treatment.
AK nutrient testing appears to reflect the nervous system's efferent response to the stimulation of gustatory and olfactory nerve receptors by various tested substances. There is considerable evidence in the scientific literature of extensive efferent function throughout the body from stimulation of the gustatory and olfactory receptors.
For example, the tester might repeat the test with a particular substance under the subject's tongue; if the muscle tests weaker than the first test, that substance is determined to be harmful. The tester may also have the subject touch a particular body part with the opposite hand. For example, to "localize" testing to the heart, the subject would place a hand over the heart. A strong arm muscle test suggests a healthy heart, while a weak test suggests a problem. Instead of sublingual testing, some practitioners have the subject simply hold a substance or place the substance near a particular organ. Some AK practitioners go as far as to hold a sealed container of the substance to be tested on the forehead, chest, etc. and then perform the test.
Another commonly used technique in AK is to have the subject wear colored glasses (blue, green, red, etc.) and perform the muscle monitoring while wearing each color of glasses. The color that causes the greatest perceived smoothness of reaction gains might be a color that is in some way beneficiens to the client. There are many tests believed to reveal information about the subject's condition.
There are now several websites [4] that display much of the Index Medicus Peer-Reviewed research papers regarding applied kinesiology, but they blend articles on AK with articles on academic kinesiology, so they must be examined with caution to avoid confusion. These papers go from 1915 (Journal of the American Medical Association, with a paper called "A method of testing muscular strength in infantile paralysis" by Martin EG, Lovett RW, (which has nothing to do with AK) to papers from 2006 from Journals like Physical Therapy, The Journal of Manipulative and Physiological Therapeutics, and the Journal of Electromyography and Kinesiology, many of which likewise have nothing to do with AK.
Proponents of AK provide what they believe to be evidence about the methods, clinical efficacy, and neurologic rationales of applied kinesiology examination and treatment. [5].
However, there is scientific research (below) of Applied Kinesiology that has shown it has no clinical validity. For example, muscle testing cannot distinguish a test substance from a placebo under double-blind conditions, and the use of applied kinesiology to evaluate nutrient status is no more useful than random guessing.
The studies, research and reviews of applied kinesiology mentioned above are listed at the National Library of Medicine and National Institutes of Health.[6][7][8] [9] [10] [11] [12]
Scientific studies showed that applied kinesiology tests were not reproducible. [13][14][15][16][17]
Robert Todd Carroll has noted that AK is an example of magical thinking.[18]
According to the American Chiropractic Association, Applied Kinesiology is one of the 15 most frequently used chiropractic techniques in the United States, with 43.2% of chiropractors employing this method.
According to a March 26, 1998 letter from the DKF (Dansk Kiropractor-Forening - Danish Chiropractic Association), following public complaints from patients receiving homeopathic care and/or AK instead of standard (DKF defined) chiropractic care, the DKF has determined that applied kinesiology is not a form of chiropractic care and must not be presented to the public as such. AK and homeopathy can continue to be practiced by chiropractors as long as it is noted to be alternative and adjunctive to chiropractic care and is not performed in a chiropractic clinic. Chiropractors may not infer or imply that the chiropractic profession endorses AK to be legitimate or effective, nor may the word/title chiropractic/chiropractor be used or associated with the practice of AK. [20]
The electrical source is the muscle membrane potential of about −70mV. Due to the applied method, the resulting measured potentials range between less than 50 μV and 20 to 30 mV.
Typical repetition rate of muscle unit firing is about 7–20 Hz, depending on the size of the muscle (eye muscles versus seat (gluteal) muscles), previous axonal damage and other factors. Damage to motor units can be expected at ranges between 450 and 780 mV.
To perform EMG, a needle electrode is inserted through the skin into the muscle tissue. A trained medical professional (most often a physiatrist, neurologist, or physical therapist) observes the electrical activity while inserting the electrode. The insertional activity provides valuable information about the state of the muscle and its innervating nerve. Normal muscles at rest make certain, normal electrical sounds when the needle is inserted into them. Then the electrical activity when the muscle is at rest is studied. Abnormal spontaneous activity might indicate some nerve and/or muscle damage. Then the patient is asked to contract the muscle smoothly. The shape, size and frequency of the resulting motor unit potentials is judged. Then the electrode is retracted a few millimeters, and again the activity is analyzed until at least 10-20 units have been collected. Each electrode track gives only a very local picture of the activity of the whole muscle. Because skeletal muscles differ in the inner structure, the electrode has to be placed at various locations to obtain an accurate study.
A motor unit is defined as one motor neuron and all of the muscle fibers it innervates. When a motor unit fires, the impulse (called an action potential) is carried down the motor neuron to the muscle. The area where the nerve contacts the muscle is called the neuromuscular junction, or the motor end plate. After the action potential is transmitted across the neuromuscular junction, an action potential is elicited in all of the innervated muscle fibres of that particular motor unit. The sum of all this electrical activity is recorded as a motor unit potential. This electrophysiologic activity is evaluated during an EMG. The composition of the motor unit, the number of muscle fibres per motor unit, the metabolic type of muscle fibres and many other factors affect the shape of the motor unit potentials in the myogram.
Nerve conduction testing is also often done at the same time as an EMG.
Because of the needle electrodes, EMG may be somewhat painful or extremely painful to the patient, and the muscle may feel tender for a few days. There also exists "needleless EMG"—an EMG performed using surface electrodes—though it gives much less accurate results with a higher level of disturbance from the surrounding environment.
Muscle tissue at rest is normally electrically inactive. After the electrical activity caused by the irritation of needle insertion subsides, the electromyograph should detect no abnormal spontaneous activity (i.e. a muscle at rest should be electrically silent, with the exception of the area of the neuromuscular junction, which is normally electrically very spontaneously active). When the muscle is voluntarily contracted, action potentials begin to appear. As the strength of the muscle contraction is increased, more and more muscle fibers produce action potentials. When the muscle is fully contracted, there should appear a disorderly group of action potentials of varying rates and amplitudes (a complete recruitment and interference pattern).
Abnormal results may be caused by the following medical conditions (please note this is nowhere near an exhaustive list of conditions that can result in abnormal EMG studies) :