By David Lemke
sEMG Equipment & Testing
Several years ago I worked with a company that had me test every sEMG system available in order to determine which equipment would be best suited to their sEMG consulting business. I chose Noraxon instruments because I believe they are the best – and the company is great to work with.
When I perform a kinesiological surface electromyography evaluation I use Noraxon’s 8 channel Desktop DTS (direct transmission system) or their MyoSystem 1200, and on occassion their wireless G2 system if I’m monitoring from greater distances. You can learn about these systems at: www.noraxon.com.
Noraxon’s MyoResearch software allows me to record simultaneous video for reference and effortlessly extract the information I need from the tracings. Let me share some guidelines I follow when performing an sEMG evaluation i.e. principles and examples of my favorite movements as well as some of my favorite muscles. Then I’ll share some interesting observations.
1. I use simple, easy to perform movements with clearly established muscle actions;
Learned, habitual muscle patterns, including compensation patterns, are most evident when the system is not struggling to execute complex movements or being made tired by strenuous tasks. A simple arm raise, a prone or standing hip extension, or simply standing on one leg – can reveal much.
2. Complex movements;
Walking is on my list of complex movements. Walking is alternating standing on one leg – so I use observations from that more simple task to understand their walking pattern or gait. Activities like the golfer’s pick up or a jump and landing test can give tremendous insight into localized instabilities.
3. Movements or activities promoting fatigue;
I save fatigue tests for last in an evaluation. Obviously I want to observe what is normal and natural during the simplest, most fundamental movements – so fatigue must wait. However, my first step in data interpretation is analyzing fatigue. Median frequency analysis pinpoints which muscles get tired first and exactly what and when and how the system compensates for the loss of that muscle’s contribution to a particular movement or activity. And it may seem obvious, but I have repeatedly observed that the compensation strategy used in fatigue evoking activity provides insight into the simpler tasks performed early in the evaluation. If there’s one thing you can count on in the body: once something is learned, when the going get’s tough, it will be used!
There are approximately six hundred and forty muscles in the human body. Muscle counts vary like how planet counts vary: Pluto may or may not be a planet – more linked to differing definitions than new information. Anyway, part of my job is deciding which muscles to listen to – so over the years I’ve found my favorites and the winners have to meet a few requirements:
1. If you’re looking for functional reference muscles, preferably stick with muscles crossing a single joint;
The more motion on either end of anything, the more complicated it’s action will be…I worked as an administrator for a school once where the board and the entire body of parents, students, etc. were each chewing on an opposite end of me – so believe me, I know life is simpler for the single joint agonist. And simpler action means more reliability and reproducibility in tests across your subject population.
Anchored centrally: SCM, upper or lower trapezius, posterior deltoid, gluteus maximus
Others: Serratus anterior
2. For pathology-linked, double joint muscles, monitor those with known antagonists and synergists;
The rule I follow here: when attempting to understand muscle function, devour the literature and reproduce tests developed by the top researchers – there’s nothing that builds confidence like testing your own patients and seeing for yourself.
Flexors versus extensors: Gluteals and lumbar paraspinals oppose deep hip flexors – a lot can be extrapolated from data drawn from any one of these. Forearm flexors and extensors – their impact/ influence on carpal tunnel space and function is established, along with hamstrings versus quads – and whether full hip extension is available. Also biceps brachii versus triceps, SCM versus cervical extensors in forward head posture, etc.
3. Monitor muscles that function in well established firing patterns;
Here again I follow paved paths. Researchers like Janda, DeLuca, Basmajian and others provide the perfect starting point for any tests you might perform – and their insights act as a launch pad for your own ideas once you’re observing your people “in the wild”.
Vladimir Janda describes the ideal firing sequence of hamstrings, gluteus maximus, and lumbar paraspinals in prone hip extension. Watching your own patients deviate in their unique ways from this established norm provides insight – or at the very least food for thought. I can’t say how many times I’ve awoken in the middle of the night after observing a pattern that made no sense – and connected with a unique challenge of that particular patient. What a delight to approach the next session with a strategy customized to that individual – and how satisfying when a new innovation produces a positive result!
Patterns & Pathologies
Below is a list of common lower body pathologies and what I believe underlies them. I will present upper body pathologies another time.
Typical symptoms and / or complaints are given on the left in the table below. Immediately to the right are muscle patterns / imbalances observed with sEMG in the case of such a complaint. Far right are what I believe to be core structural-functional patterns that underlie the muscle imbalances.
Core Pattern & Lower Quarter (08-15-12)
|Symptoms / Complaints||LQ Dysfunctions||Core Pattern|
|Right or left piriformis syndrome||Right gluteal inhibition with right piriformis and TFL substitutionRight piriformis short and tight in concentric phase left piriformis stressed due to eccentric phase contracture||*Location of Heart & Liver = Diaphragmatic AsymmetryIntermingling of Psoas & Diaphragm fibers = Rotated Ilium: Right Posterior / Exterior; Left Anterior / Interior*Not tested with sEMG|
|Knee pain, issue from VMO dysfunction;Vastus lateralis TrP – often mistakenly diagnosed as ITB syndrome||Right VMO tone depression impairs patellar tracking – impairs vastus lateralis (shortness insufficiency in an extension muscle) – Vastus lateralis TrP / irritable motor point deep to ITBjust above the knee||Rotation of Femurs off central axis due to asymmetric pelvic rotation – force redirected through ill-suited muscle fibers|
|Quadratus Lumborum TrP activity with low back painLow back pain from lumbar paraspinal dysfunction, ligament, and disc distress||Right adductor tone elevation impair left QLRight hamstring and gluteal dysfunction with lumbar rotation to right increases right paraspinals to hypertonus||Asymmetric Psoas tone Asymmetric Gluteal toneBilateral Rectus Femoris length-tension dysfunction (tone elevation) = Bilateral Hamstring Inhibition|
|Anterior hip pain – arthritis diagnosis with possibly inappropriate (invasive) treatment||Loss of bilateral hip extension necessitates rectus femoris proximal head dysfunction – eccentric on left / concentric on right||Leading with the right leg / loading more on the left|
|TFL TrP patterns include sciatic like symptoms, ITB syndrome||TFL compensatory hypertonus||Chronic gluteal inhibition necessitates TFL / piriformis compensation. Flexion dominance = chronic extension pattern agonist inhibition.|
|Shin splints, plantar fasciitis, achilles tendonitis||Loss of hip extension concurrent with reduced plantar / dorsiflexion – and hypertonic soleus inhibiting tibialis anterior; peroneals hypertonic due to force not traveling through central axis when under load; elevated unilateral soleus tone (typically right side) = achilles tendon cross section area asymmetry > 30%Chronically inhibited plantar muscles = increased load on foot tendons and ligaments||Chronic systemic inhibition of extension pattern agonistsPrevalence of right posterior and left anterior pelvic rotation = reduced right hip extension|
The elusive twenty-five percent…
The information in the right hand boxes are critical: at its core the human body is not symmetrical. There is a functional “twist” that impairs so much normal function – but we’re drawn to focus on the abnormal – the pathological – because that’s where it hurts. I was forced to look deeper because of sEMG data. I was seeing the same muscle patterns showing up in nearly everyone I evaluated – including the perfectly healthy ones!
The human learning system cannot function symmetrically because it is not built symmetrically. And if the system has learned every motion on top of a twist, it follows that when the going gets tough – whether the cause is fatigue, stress, dehydration, grief, or pain, we will all do what comes easiest – and all human beings exhibit predictably (twisted) defensive behaviors. These behaviors are specialized and always overuse or underuse the same muscles – assuring loss of circulation to muscles and nerves with the resulting loss of muscle inventory opening up passive support tissues to excessive stress.
Throw out the data or change your thinking
I was asked at a biomechanics conference to share how I deal with “problem data”. I have always let the data do the talking since it is unbiased – in fact it was the problem data that forced me to look deeper and not be satisfied with a seventy-five percent solution. The benefit of looking deeper is that we see a system that has predictable defensive movement biases that are always involved to some extent in a very long list of problems. These biases can be measured and studied. And if better understood then countering the biases means injuries and pathologies can be reduced and ultimately prevented.
In part IV I will close by sharing my most recent discovery: a way to cross train out of the twist – using absolutely zero effort!