Obtaining accurate, reliable readings with the Static sEMG

For over 15 years, doctors throughout the world have relied upon the MyoVision Static sEMG system as perhaps the most reliable systems available.  Test-retest reliability is excellent with the machine, but due to the nature of Static sEMG testing, human error needs to be minimized.  Most issues with Static sEMG testing are resolved through applying consistent testing technique.Please view the "Basic Video Training for Static sEMG on the main Technical Support page, or in your MyoVision software by clicking the TRAINING button.  This 4 minute video provides information on proper testing technique, and can resolve most technical issues.

What kind of reliability can I expect from Static sEMG?

Let's talk about blood pressure for a moment.  As you know, blood pressure is a very important physiological test which is used every day throughout the world as a measure of general health .  Did you know that this measure has a test-retest reliability of only 0.83?  This means that it is reproducible only 83% of the time!  But we still use it.  Needle sEMG which is well accepted has a test-retest reliability rating between 0.25 and 0.62 meaning it is reprodicible only 25 - 65 percent of the time.Just like blood pressure, their are many variables which regulate all physiologic tests, and this is why you should not expect a test-retest reliability greater than .70-.80 for your MyoVision Static sEMG.

The MyoVision Dynamic SEMG may provide higher test-retest reliability for certain tests, but Static sEMG is limited by:  

1.  Readings are done by a human placing electrodes against the skin.  Certain variabliity will be caused by human error. 

2.  Test will vary based upon activities performed by the patient.

3.  Tests will vary due to shoe height, so it is best to have patients remove their shoes.Although there is variability inherent in all physiological tests, it does not preclude us from performing these tests.  There is tremendous value from utilizing these tests as ONE OF THE MEASURES we use to put together a clinical profile.  A 15-20% variation is considered acceptable for all physiological tests.What is the purpose in using physiological insturments?

1. We are detectives, and detectives gather evidence.  Just as a medical doctor will use blood pressure as ONE indicator of health, it is never relied upon entirely for a clinical decision.  It is only an indicator.  Detectives gather evidence of all kinds in developing a clinical profile. Just as with MRI which has a 40% false positive rating, interpretation is important with all physiological tests.  Interpretation is developed through experience and training.  PLEASE review the "interpretation video" found under the "Training" button in your MyoVision software.
2. Experience leads to significantly better reliability and interpretation skill.  Just as you did not learn your skills as a doctor overnight, you will need a couple of months and at least 50 tests before you truly understand the value of the exam.

What do we look for?

It is more important to look for patterns in the readings, then the actual readings themselves.  In other words, instead of focusing on the readings you have at C6 on the right, look at the overall balance of muscle activity about the entire spine.  This "balance" tells the story, letting us know how the muscles are firing for the purpose of compensation.

How do I obtain the most accurate, reproducible readings?

Assuming you have watched the video training in your software, and reviewed the technical hardware issues one web page level up from here, the following are important tips:

1. Make certain that your electrodes are good.  In general electrodes last anywhere from 6 months to two years. For best consistency, wipe the skin down left and then right sides of the skin with an alcohol wipe.  Make sure the skin is DRY before proceeding.  Use a paper towel to "dab" the skin dry if in very humid environments. Always use a hair clip to hold the hair up, and not rubber bands.  Rubber bands can cause high readings by pulling on the hair. It is always best to test with shoes off, but especially with women as their shoe height varies more than with men. Always use fresh Quickscan pads.  If you choose to reuse the pads, they will lose their conductivity. Make certain to place 1-2 Quickscan Pads ON TOP of the lid of the Quickscan Pad jar.  NEVER place the probes into the jar itself, as you will splash liquid onto the probes shorting out electrodes.  Also, you will wear out the electrodes faster as their is increased friction as they rub on the pads as pressure is place on them. Touch down the probe to the Quickscan pad prior to EVERY measurement (each level you are measuing). Make certain that all three electrodes contact the Quickscan liquid. Make sure you are touching the electrodes to skin and NOT hair.  Move electrodes out under the ear if necessary to avoid hair, as hair will cause very high readings as you are not contacting the skin.  If you are scanning a very hairy individual, you can shave if only a small area, or use the Signa Cream on each electrode.
   
   When using Signa Cream, place a dab of it on each electrode, and carefully place the probes against the skin WITHOUT moving them once placed.  If you move the electrodes along the skin, you will be wiping the signa cream between electrodes causing a "bridging" or "shorting" of the electrodes which can cause high or low readings.
     Watch the screen after touching electrodes to the skin.  Proof that you have good contact with the skin is a quick drop in the readings.  Once you see the readings make the initial drop, press AND RELEASE only ONE of the buttons (left or right).  One button will initiate the AUTOSCAN process, where the computer stores data ONLY after the readings have stabilized.  It was designed with two buttons to accommodate left or right handed individuals.
2. If you need to REDO a sight, simply click the mouse on the site (at the center of the spine) you want to redo, and test again.  You may have to click on the level you want to test next in certain circumstances.