EMG - what is it and what to expect
I recently acquired an EMG machine for objective testing at work. Why get one and what is it?
EMG stands for Electromyography and it “..is the study of muscle function through the inquiry of the electrical signal the muscles emanate.”
There are many ways to assess an individual using an EMG, either via a skin surface electrode (limitation is that only surface muscles can be detected) , vaginal and anal probes (for pelvic floor muscle evaluation special anal and vaginal probes are established, e.g. often used for incontinence testing and biofeedback training) and fine wire electrodes (thin and flexible fine wire electrodes are the preferred choice for invasive electrode application within deeper muscle layers)
The use of EMG starts with the basic question: “What are the muscles doing?” Typical benefits are:
1. EMG allows us to directly “look” into the muscle 2. It allows measurement of muscular performance 3. Helps in decision making both before/after surgery
4. Documents treatment and training regimes 5. Helps patients to “find” and train their muscles
6. Allows analysis to improve sports activities 7. Detects muscle response in ergonomic studies
Besides basic physiological and biomechanical studies, kinesiological EMG is established as an evaluation tool for applied research, physiotherapy/rehabilitation, sports training and interactions of the human body to industrial products and work conditions:
Above is a Work/Rest assessment on a knee.
The test was performed on a post surgical ACL patient, assessing her VMO (vistas medals oblique) muscle at 0 degrees of knee flexion. She was sitting in an upright position and knee angle was measured at 0 degrees using a goniometer (this is a tool to measure the range of motion accurately using the bodies bony landmarks as a reference point).
It works as a 5 second rest, 5 second work process, 5 times.
By testing we can measure the difference between the left and right leg and see which leg is weaker, and by how much at that specific range of motion. An adjustment of the program would occur and then a reassessment would conducted to see the affects of the adjusted protocol on the knee strength, which is evaluated by using the same tests.
As Biokineticists we must provide the most objective data to our patients and allow them to not just "feel" progress, but to see it visually and track this change. Through this process, we can react and change rehab to fulfil its ever changing goal posts.
Does this make sense so far? If it's a lot to take in - read the paragraph above again.
The uses and advantages of EMG are vast. It supplies objective findings which are not obtainable by any other means. There is direct observation of impulse from the muscle fiber itself, without intermediary procedures which could add interference.
EMG testing is very demanding and time consuming; if you are to use it, be prepared to invest this time and energy for you and your patients. This can allow you to start training the right areas either via the use of an EMS machine (electric muscle stimulation) as an adjunct to rehab, using this in an "isolated" form or a functional form, during exercise sessions or by identifying the deficits in the tested muscle group, to give more attention (i.e.: sets, reps, time under tension and loading), to the muscle groups engaged in certain exercises.
EMG can only answer its specific categories of questions. Like any other biomechanical method, it acts like a lens, by focusing on one selected subsystem or component of a very complex overall biological system. Muscles are the “motors” (or brakes) of locomotion, but by their nature they only receive and operate reflex based or CNS driven commands. EMG of a muscle alone can never answer a “Why?”. This makes interpretation very demanding and requires a fundamental understanding of the entire sensory-motor system. A single biological finding is worthless if it is not integrated into the entire system, meaning we must take all factors into account, e.g.: cognitive/emotional processes, active motor system, connective tissue, cardiovascular system etc.
For a test to be as accurate as possible, the assessor must keep as many factors as possible constant or controllable by other measures.
Keep range of motion, velocity, repetitions, fatigue status the same and change only the load from zero kilograms, to 2 kilograms (fixed to a varied load) to see the change in response from the first test to the next. This allows us to analyse the findings of the EMG to illustrate muscle function.
There is so much research out there for training, find what works for you.
"The good thing about science is that it's true whether or not you believe in it." This is from my favourite TV show the Big Bang Theory. Science is there for us to be objective. Speak from facts, limit opinion when It comes to testing, and we begin to create objective testing and repeatable tests that allow us to see and track progress and decline, and find out how to manage our patients and athletes the best way we can, through scientifically based exercise programming and design.
Consult your medical professional and Biokineticist for more advice and guidance on your training and these other areas:
Gait and Posture analysis
Active training therapy
Cardiac and Pulmonary Rehabilitation
Orthopeadic Injuries and rehabilitation