surface electrode emg

7/27/2019 Surface Electrode Emg

1/86

Surface Electromyography

(SEMG)

Presented By:

Joseph S. Ferezy, D.C.


2/86

Initially, Claims Made by theManufacturers Were Frankly

Outrageous, and It Was Easy toBrush Paraspinal EMG off As

Useless.


3/86

More Recently, However,

Literature Is Beginning to

Accumulate, and Manufacturers

Appear to Have Upgraded theQuality of the Equipment While

Downgrading the Claims.


4/86

When the Doctor Looks for

Answers, It Seems That Only the

Manufacturers and DistributorsAre Supplying Them.


5/86

The Purpose of This Presentation

Is to Sift Through the Claims,

and Examine the FactsRegarding Paraspinal EMG.


6/86

You Should Not Consider

Buying a Device WhichMeasures Something If You

Cannot Answer Three Questions: What Am I Measuring, and What Is Known

About It?

Is the Device Giving Me an Accurate Measure?

What Useful Clinical Information Can BeGleaned From This Measurement?


7/86

This Weekend, I Will Attempt to

Present the Facts Necessary toThink Through Each of the

Above Questions. In Doing So,Each of You Will Be Able to

Make up His/her Own Mind, and

Not Just Listen to My Opinions.


8/86

Without This Requisite

Background, One Has No

Chance at All of Critically

Examining the Utility of ThisTechnology, in Regard to Their

Personal Clinical Needs.


9/86

There Are Numerous Problems Which

Must Be Overcome Before One Can Say

That They Can "Measure Spasm". WhatExactly Is a Spasm? There Is an

Embarrassing Lack of Information

Related to Measuring Muscle Spasm,and the One Study of Interexaminer

Reliability Shows Lousy

Reproducibility. Ironically, Our

Assessment of It Significantly Effect the

Lives of Millions of People Each Year.


10/86

Surface Electrodes

"What Is Better, Surface Electrodes or

Needle Electrodes?"


11/86

This Is Really an Apples and

Oranges Question, or at Least a

Question Which Is

Oversimplified And, Hence,

Unanswerable. For WhatPurpose Is the Electrode Is Being

Used? It Would Be QuitePainful to Look for Insertional

Activity With a Surface

Electrode.


12/86

It Is Generally Accepted That a

Surface Electrode Is Superior for

the Assessment of Global

Myoelectric Activity. If You

Are Looking for GeneralActivity of Muscle Tissue in a

Particular Area, the SurfaceElectrode Is Superior.


13/86

If You Are, However, Looking

for Information Regarding aSpecific Piece of a Specific

Muscle, Then a Needle or Wire

Has an Obvious Advantage. In

Fact, Even Tiny Movements (.1

Mm) Can Significantly Alter theDay to Day Reliability of Needle

Electrodes.


14/86

Most Equipment Manufacturers Will

State That Surface Electrodes Are More

Reliable, and Site Papers As Sources of

Proven Reliability (Reproducibility). It

Should Be Noted That Virtually All of

These Studies Regard Peripheral

Musculature. Spector at New York

Chiropractic College Did Do a Very

Good Study on Paraspinal Muscles and

Attached Surface Electrodes, Reporting

Excellent Reliability Coefficients.


15/86

If the Readings From Attached

Surface Electrodes Are Reliable,

We Must Next Ask How Does

the Procedure of "Scanning"Emg Compare to Attached

Surface Electrodes.


16/86

Thompson Et. Al. And the Mayo

Clinic Study Are Often Sited As

Proof of Scanning Electrode

Reliability As Compared to

Attached Surface Electrodes.Attached Surface Electrodes

Were Never Even Used in ThisStudy.


17/86

Thompson Was Attempting to

See If a 2 Second Average of

Integrated (MAP) Was Sufficient

for a Reliable Reading. His

Conclusion Was That It WasNot. He States That Only 37%

of the Sites Sampled Fell Withinan Acceptable Range With a

Two Second Scan.


18/86

One of His Conclusions Stated, "a

Longer Integration Period Enhances

the Validity" and "A 10 SecondIntegration Period Would Improve

the Quality of the Data Obtained..."

This Raises a Significant QuestionAs to the Reliability of Scanning

Electrodes. A Properly DesignedReliability Study for Scanning

Electrodes Versus Attached Surface

Electrodes Should Be Undertaken.


19/86

Once the Issue of Reliability Is

Addressed, One Must Ask If the

Reading Is an Accurate

Reflection of Myoelectric

Activity. To Determine This, LetUs First Consider Variables

Regarding Apparatus Detectionand Recording of Signals.


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Basmajian and Deluca

"It Is Important to Remember That the

Characteristics of the Observed EMG

Signal Are a Function of the ApparatusUsed to Acquire the Signal As Well As the

Electrical Current Which Is Generated by

the Membrane of the Muscle Fibers".


21/86

If the Filter Is Narrow at the

Point of Signal Acquisition, It

Does Not Matter What Band

Width Is Available From ThatPoint on. Like a Funnel Turned

Upside Down.


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Tissue Filtering

The Amplitude of Action

Potentials Decreases to

25% Within 100 um.

The Thickness of the

Fatty and Skin Tissues

Must Also Be

Considered.

The Tissue(s) Behaves

As a Low-pass FilterWhose Bandwidth and

Gain Decreases As the

Distance Increases.

The Muscle Tissue Is Highly

Anisotropic. Orientation of

the Detection Surfaces of theElectrode With Respect to

the Length of the Muscle

Fibers Is Critical.

Dirt, Oils, Etc. Must Be

Removed From the Skin, So

That They Do Not Distort

the Signal. This Can Be

Accomplished by Cleaning

the Skin With an Abrasive,Or, Minimally Wipe It With

Alcohol and Allowed to Dry

Prior to Taking a Reading.


24/86

Electrode-electrolyte Interface

Behaves As a High-pass Filter. The Gain

and Bandwidth Will Be a Function of the

Area of the Detection Surfaces,Electrolytic Treatment of the Surfaces, and

Any Chemical-electrical Alteration of the

Junction. The Detection Surfaces Should Always Be

Kept Clean.


25/86

Bipolar Electrode Configuration

This Property Ideally Behaves As a Band-passFilter. However, This Is Only True If the Inputs tothe Amplifier Are Balanced and If the Filtering

Aspects of the Electrode-electrolyte Junctions AreEquivalent.

A Larger Interdetection Surface Spacing WillRender a Lower Band-width. This Aspect Is

Particularly Significant for Surface Electrodes. The Greater the Interdetection Surface Spacing,

the Greater the Susceptibility of the Electrode toDetecting Measurable Amplitudes of Emg Signals

From Adjacent and Deep Muscles.


26/86

Bipolar Electrode Configuration

A Rule of Thumb Is That the Electrodes Will

Detect Measurable Signals From a Distance

Equal to the Interdetection Surfaces Spacing.However, the Anisotropy of the Tissues Beneath

the Electrode May Augment the Sensitivity of

the Electrodes Along the Surface of the Muscle

Creating Cross-talk.

An Interdetection Surface Spacing of 1.0 Cm Is

Recommended for Surface Electrodes.


27/86

Amplifier Characteristics

Values Should Minimally Distort the EMG

Signal Detected by the Electrodes.

Length of the Leads to the Preamp Should

Be As Short As Possible and Should Not

Be Susceptible to Movement. The

Necessity of This Precaution IsAccentuated When Amplifiers With High

Input Impedance Are Used.


28/86

Typical Settings and

Characteristics for the Amplifier Gain: Such That It Renders

the Output With an

Amplitude of Approximately

+- 1v. Input Impedance > 10-12

Ohms Resistance in Parallel

With 5 Pf Capacitance.

Common Mode Rejection

Ratio: > 100 db.

Input Bias Current: As Low

As Possible (Typically Less

Than 50 Pa).

Noise < 5uv RMS.

Bandwidth (3 Db Pointsfor 12 Db/octave

Rolloff).

Surface Electrodes 20-500 Hz.

Wire Electrodes 20-1000

Hz. Monopolar and Bipolar

Needle Electrodes forGeneral Use - 20-1000

Hz.


29/86

The Bandwidth Filter of the Amplifier Is

a Point of Contention Among

Manufacturers. Median Frequency of

the Power Density Spectrum Appears to

Provide an Appropriate Representation

of Biochemical Events Within the

Muscle. It Is Well Documented That in

Sustained, Constant Force IsometricContraction, a Shift Toward Lower

Median Frequencies Occurs, As the

Muscle Fatigues.


30/86

Along With Decreasing

Frequency Is an Increase in

Amplitude. These Phenomenon

May Be Due to Recruitment of

Muscle Fibers, Motor UnitSynchronization, And/or

Conduction Velocity Changes ofMuscle Fibers.


31/86

One Must Carefully Define the

Term "Muscle Fatigue" Before

Determining How the

Phenomena of Greater

Amplitude and Lower Frequencyof Emg Signal During Active

Voluntary Muscle ContractionCan Be Clinically Applied.


32/86

Physiologically, Muscle Fatigue

Does Not Happen All at Once.

Histologically There Is No

"Point of Fatigue", Just a

Continuum of Chemical ChangesLeading to an Eventual Clinical

Failure of the Patient to Performthe Task.


33/86

The Emg Signal Under

Voluntary Muscular Activity

Has Been Extensively Studied.

It Is Expressed As a Percent of

(MVC). It Holds ExcellentProspects for Clinical

Application in Assessment ofBack Pain Patients.


34/86


35/86

Whether This Is the Same As

"Spasm" Is Doubtful.

Methodology for Signal

Acquisition Must Be

Meticulously Performed,"Placement Determination by

Bony Landmarks IsUnacceptable".

Roy and Deluca


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Other Considerations

It Is Preferable to Have the Subject, the

Electrode, and the Recording Equipment in an

Electromagnetically Quiet Environment. However, If All the Procedures and Cautions

Discussed Are Followed and Heeded, High

Quality Recordings Will Be Obtained in the

Electromagnetic Environments Found in Most

Institutions, Including Hospitals.


37/86

Where To Locate The Electrode

If One Is Measuring EMG Frequency

Parameters, It Is Essential to Avoid

Placement of the Electrode Near the MotorPoint.

Signal-to-noise Ratio.

Signal Stability (Reliability).

Cross-talk From Adjacent Muscles.


38/86

A Recent Article by Wolfe,

Wolfe and Segal From Emory

University Reveals That

"Extraneous Movements Such

As Neck Flexion and PelvicRotation Can Elicit Profound

Activity From PercutaneouslyPlaced EMG Electrodes While

Little Change Is Seen at the Skin

Surface."

S Ti Fil i El d


39/86

So, Tissue Filtering, Electrode-

electrolyte Interface (Skin Preparation),

Electrode Configuration, AmplifierCharacteristics, Recording

Characteristics, Electrode Location and

Other Considerations Will All Effect theAccuracy of the Signal Being Measured.

It Is Important to Check Into

Manufacturers Specifications andApproaches to Each of These Variables,

and See If They Are Satisfactorily

Considered.


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What Useful Information Can Be

Obtained By Measuring Global

Myoelectric Activity?


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This Is a Difficult Question to

Answer. Much Available LiteratureIs Not Published in Peer Reviewed,

Referred Journals and Even the

Referenced Literature Is Filled WithQuestionable Methodologies,

Contradictions and Hardware

Considerations. Let Us Begin With

a Review What Is Known Regarding

Paraspinal Muscle Function.


42/86

Commonly They Comprise (From

Superficial to Deep): the

Semispinales, the Multifidi, and the

Rotatores Muscles.

Some Contend That Deep RotatorMuscle Paralysis Is the Cause of

Idiopathic Scoliosis. It Has Been

Demonstrated That There IsIncreased Muscular Activity on the

Convex Side of the Scoliotic Curve.


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45/86

As the Slowly Flexing Trunk Is Lowered, the

Activity in Erector Spinae Increases Apace

and Then Decreases to Quiescence WhenFull Flexion Is Reached. If an Attempt Is

Made Then to Force Flexion Further, Silence

Continues to Prevail in the Erector. In FullFlexion, Then, the Weight of the Torso Is

Borne by the Posterior Ligaments and

Fasciae-the Posterior Common Ligament, the

Ligamentum Flavum, the Interspinous

Ligaments, and the Thick Dorsal

Aponeurosis.

i h h bj di h


46/86

With the Subject Standing, the

Activity in Erector Spinae

Ceases Earlier During Forward

Bending Than It Does When

Seated. In Some Patients TheyFind Complete Relaxation in the

Sitting but Not the StandingPosture.

S di A i i i h


47/86

In Standing Erect, Activity in the

Erector Spinae Is Not Required,

Except for Forced Extension. In

the Initial Stages of Flexion of

the Trunk in Bending Forward,the Movement Is Controlled by

the Intrinsic Muscles of theBack.


48/86

It Has Also Been Shown That

the Position of Full FlexionWhile Seated (Slouching) Is

Maintained Comfortably for

Long Periods and That During

This Time the Erector Spinae

Remains Relaxed.

S bj S di i


49/86

In Most Subjects Standing in a

Relaxed Erect Posture Showed a

"Low Level of Discharge" in the

Erector Spinae. Small

Adjustments of the Position ofthe Head, Shoulders, or Hands

Could Be Made Which WouldAbolish the Activity of the

Muscle, I.E., An Equilibrium or

Balance Could Be Achieved.


50/86

From the Easy Upright Posture,It Has Been Found That

Extension (Hyperextension) of

the Trunk Is Initiated, As a Rule,

by a Short Burst of Activity.


51/86

While Standing Upright

Flexion of the Trunk to One Side IsAccompanied by Activity of the Erector Spinaeof the Opposite Side "Antagonist.

If the Back Is Already Arched in Hyper-extension, Not Even This Sort of ActivityOccurs.

The Recording of Activity From Both Right andLeft Erectores During Bending to Either SideHas Also Been Shown, and There Is a Pattern ofCooperative Activity and Not a Simple

Simultaneous Antagonism.

Erectores Spinae Contract


52/86

Erectores Spinae Contract(Vigorously) During Coughing

and Straining. This Occurs Evenin the Midst of Their Normal

Silence, Whether the Subject Is

Erect or "Full-flexed." The

Clinical Implications of This

Last Observation Should BeExplored.

It Has Also Been Reported That the


53/86

It Has Also Been Reported That the

Erector Spinae Remained Relaxed

During the Initial Movement ofLifting Weights of up to 56 Lbs. It

Is Movement at the Hip Joint That

Accounts for the Earliest Phase ofApparent Extension of the Trunk.

However, the Ligaments of the BackWere Required to Carry the Added

Weight Without Help From the

Adjacent Muscles.

D i th P f f V i


54/86

During the Performance of Various

Trunk Movements, Deep Muscles

Showed Patterns of Activity ThatClearly Showed Two Functions,

Sometimes They Initiate Movement,

and at Other Times They Stabilize

the Trunk. Almost All the

Movements Recruit All the Musclesof the Back in a Variety of Patterns,

Although the Predominance of

Certain Muscles Is Also Obvious.

In Compound Movements, When Subjects


55/86

In Compound Movements, When Subjects

Are Not Trying to Relax, There Is Constantly

More Activity Than When the Movement Is

Carried Out Deliberately and WithConscious Effort to Avoid Unnecessary

Activity of Muscles. Complete Relaxation

and Lower Levels of Contraction Are the"Ideal" Rather Than the Rule for Normal

Bending Movements. Muscles That Might

Be Expected to Return the Spine to theVertical Position Often Remain Quiet; That

Suggests That Such Factors As Ligaments

and Passive Muscle Elasticity Play anImportant Role.

A Position of Complete Silence


56/86

A Position of Complete Silence

Is Easily Found for Iliocostalis in

the Erect Position, but WithSlight Forward Swaying Activity

Is Instantly Recruited. ForwardFlexion and Rotation in the

Flexed Position Bring Out Its

Strongest Contractions, but It Is

Also Fairly Active in Most

Movements of the Spine.

Multifidus and Rotatores Have


57/86

Multifidus and Rotatores Have

Rather Similar but Not Identical

Activity. With Movements in theSagittal Plane, They Are Active As

They Also Are in Contralateral

Rotary Movements. Yet, Like All

the Other Muscles, These Too Relax

Almost Completely During FullFlexion, Leaving the Trunk

Practically Hanging on Its

Ligaments.


58/86

In a Systematic Exploration of the

Intrinsic Muscle of the Spinal

Column During Various Exercises

Widely Advocated for Physical

Fitness, It Was Found That theSemispinalis Capitis and Cervicis

Apparently Help to Support the

Head by Continuous Activity DuringUpright Posture. This Finding

Contradicts Other Studies.

In Almost All Vigorous Exercises


59/86

gPerformed From the Orthograde

Position, It Has Been Found That the

Most Active Muscle Is Spinalis; Next inOrder Is Longissimus, and Least Active

Is the Iliocostalis Lumborum.

Nevertheless All Three Muscles and the

Main Mass of Erector Spinae Act

Powerfully During Strong Arching of

the Back in the Prone Posture. During

Push-ups, There Is Considerable

Individual Variation But, Typically, theLower Back Muscles Remain Relaxed.

mp e e- en ng xerc ses o


60/86

p gthe Trunk Do Not Recruit Erector

Spinae As Long As There Is No

Concomitant Backward or Forward

Bending. This Clearly Refutes

Earlier Opinions Whose AuthorsHad Ignored Movements in the

Ventrodorsal Plane That Do Involve

Erector Spinae. Much of This WorkHas Been Confirmed, and the

Technique Has Been Adopted for

Er onomics b Tichauer.


61/86

Deep Muscles

Variations in the Pattern of ActivityDuring Forward Flexion, Extension, and

Axial Rotation Suggest That theTransversospinal Muscles Adjust theMotion Between Individual Vertebrae.

The Experimental Evidence Confirms the

Anatomical Hypothesis That the MultifidiAre Stabilizers Rather Than Prime Moversof the Whole Vertebral Column

Th I t t ti f El t i l A ti it


62/86

The Interpretation of Electrical Activity

Presents Some Difficulties. Did a Muscle

Showing Activity Produce the Movement,Prevent the Movement, or Was It

Contracting Isometrically? Therefore

Emphasis Must Be Placed on the Occurrenceof Electrical Silence, Knowing That the

Muscle Tested Was Not Taking Part in the

Movement Under Observation. Decreasing

or Increasing Activity During a Movement

Also Seemed to Be Functionally More

Important Than Unchanging Activity.

One Study by Anderson Et Al Attempted to


63/86

One Study by Anderson Et. Al. Attempted to

Relate Paravertebral Muscle Function to Disc

Pressures, and Found That the Amplitude of the

EMG Signal and Pressure Increased Both WithAngles of Forward Flexion and With Increasingly

Static Loads in Flexion. During Asymmetric

Loading, Pressure Values and MyoelectricActivity Increased, Being Greater on the

Contralateral Side of the Lumbar Region and

Ipsilateral Side of the Thoracic Region. The Disc

Pressure, Intraabdominal Pressure, and Semi-integrated Rectified EMG Signal Were Higher

Throughout When the Trunk Was Loaded in

Rotation, Rather Than in Lateral Flexion.

Changes in the Lumbar


64/86

g

Curvatures During Sitting and

Standing Lumbar Muscles Have Been Shown to Be Inactive

During Relaxed Sitting but Showed Some Activity in

Straight Sitting and in the Standing Posture.

This Finding Is in Agreement With the Results of Most

Other Workers.

Disc Pressure and Myoelectric Activity Change

Together. When the Back of a Seated Subject Is

Supported, Levels of Both Pressure and EMG Signal

Fall. In This Study It Was Confirmed That

Intramuscular Wire Electrodes Are Superior to Surface

Electrodes in the Study of Intrinsic Back Muscles

(Anderson Et Al, 1974, 1977).


65/86

Forward Flexion in Sitting and

Standing Positions Morris Et Al (1962) Found That Flexion-

relaxation Can Occur, but They Felt That inNormal Bending Movements the Back Muscles

Remained Frequently Active.

Spontaneous Electrical Silence of the LumbarMuscles in Extreme Flexion Has Also BeenFound in Subjects, but Only Half of ThemShowed Spontaneous Inactivity of TheirThoracic Muscles in Both Seated and StandingPostures.

Flexion/Relaxation Phenomenon


66/86

Flexion/Relaxation Phenomenon


67/86

This Flexion-relaxation

Phenomena Has Been Validated

by Numerous Studies, and Does

Appear to Be Absent in aPercentage of Low Back Pain

Patients.

During the Valsalva Maneuver


68/86

During the Valsalva Maneuver

With Increased Intrathoracic and

Abdominal Pressure While

Holding a Sandbag of 11.25 Kg,

All Thoracic and a Number ofLumbar Muscles Showed

Activity Instead of ElectricalSilence.


69/86

Extension From the Flexed to the

Upright Posture While Inactivity of the Back Muscles During the

Last Stage of Flexion Can Be Explained in Thatthe Muscles Are No Longer Needed and

Ligaments Are Holding the Vertebral Column,There Is No Explanation of Why These MusclesDo Not Always Become Active ImmediatelyWhen Extension Is Begun.

Instead, There Frequently Are Short "Bursts" ofActivity That Occur (Especially in the LumbarRegion) When the Movement of Extension IsHalf Completed.


70/86

It Therefore Appears That inMost Persons the Lumbar

Transversospinal Muscles Do

Not Initiate Extension From the

Fully Flexed Position.

Lifting Weights With Different


71/86

Lifting Weights With Different

Mechanical Advantages Seemed to

Indicate That in Most InstancesMore Energy Is Used in the Lumbar

and Thoracic Back Muscles When

the Object Lifted Cannot Be Brought

Close to the Line of Gravity of the

Subject. Investigators Also NoticedIncreased Activity of the Back

Muscles When the Center of Gravity

Was Shifted Forward.

Axial Trunk Rotation


72/86

Axial Trunk Rotation In One Study Less Than

Half of the Examined

Subjects Showed theExpected Activity of theTransversospinalMuscles of the ThoracicRegion, Whereas More

Than Half of theSubjects Showed theExpected Activity in theLumbar Region.

This Finding IsSomewhat SurprisingConsidering That Mostof the Actual RotatoryMovement Occurs in the

Thoracic Region.

Paradoxical Activity of the

Deep Muscles Was Found in

Five Subjects at the Thoracicand in Three Persons at the

Lumbar Level.

In the Lumbar Region the

Muscular Activity Seemed

More Often to Support theTheory of Rotatory Function.

On the Other Hand, the

Position of Articular Facets

in Relation to the Direction

of Muscle Pull Casts Doubton the Anatomical Feasibility

of Such a Function.


73/86

Perhaps the Designation of Specific


74/86

Perhaps the Designation of Specific

Function Is Almost Impossible in the

Back, Where We Have a ComplexArrangement of Muscle Bundles

Acting on a Multitude of EquallyComplex Joints. Those Who Insist

on Finding Prime Movers,

Antagonists, and Synergists in theGenuine Musculature of the Back

Will Be Always Disappointed.

In a Wire Electrode Study of


75/86

In a Wire Electrode Study of

Intrinsic Muscles, a Tokyo

Orthopedics Team Was Unable toProvide Validation for Reeducation

Exercises Widely Advocated and

Used in France. Rather Than

Abandon the Exercises, They

Suggested That the TransversospinalMuscles Are Stabilizers and That

This Function Is Important.


76/86

Standing

Continuous Activity of the Back Muscles in theLower Thoracic Region During Standing HasBeen Reported. The Activity of These Muscles

Appears to Depended on Their Relation to theLine of Gravity. The Segments of the VertebralColumn Located Further Posterior to the Line ofGravity Had the Tendency to Fall Forward, a

Movement That Was Counteracted by the BackMuscles. The Thoracic Muscles Showed aGreater Tendency to Remain Active, While theLumbar Muscles Acted With "Bursts" of

Electrical Potentials.


77/86

Some Muscles Apparently

Contract Unnecessarily. TheseContractions Were More Often

Seen in Women and Untrained

Men. Further Confounding Any

Attempt to Seek What Is Normal

for All.


78/86

Asymmetry

There Are Some Differences in Activity of

the Transversospinal Muscles at the Same

Levels. This Asymmetrical Activity Occurred

During Quiet Sitting and Standing but Was

Also Noted With Movements in theSagittal Plane.

Wolf and Basmajian (1980) and Wolf EtAl (1979) A bl d d A l d


79/86

Al. (1979) Assembled and Analyzed

Quantified Data Correlating Normal Back

Movements With the EMG Activity in121 Adult Subjects Who Reported No

History of Low Back Discomfort. EMG

Records Were Obtained From Vertical

Pairs of Surface Electrodes Placed

Bilaterally 3 Cm From the Midline at the

L3-4 and L4-5 Levels. Recordings Were

Made of a Range of Possible Movements

While Standing and Sitting (With the

Pelvis Stabilized).

Differences in Left- and Right-


80/86

Differences in Left and Right

sided Mobility Are Minimal

And, As Expected, Men Showed

a Significantly Greater

Excursion in VertebralSeparation During Complete

Trunk Flexion

Significantly Greater Activity Occurred


81/86

g y y

During Extension From the Flexed

Trunk Position Than Vice Versa forEach Electrode Pairing. For Rotational

Movements in the Standing or Sitting

Postures, Greater Activity Was SeenDuring Rotation Contralateral to the

Location of a Unilaterally Placed

Electrode Pair. The Magnitude of ThisActivity Level Was Not Significantly

Greater for Male or Female Subjects.


82/86

During Stooping or Squatting

Movements, MalesDemonstrated Significantly

Greater Activity Than Females

for Recordings at All Electrode

Placements, Except the Lower

Bilateral Pair.


83/86

All Results in Relation to the Mechanical

Advantage, Center and Line of Gravity, and

the Possible Axis of Movement Confirm the

Idea That the Transversospinal Muscles Act

As Dynamic Ligaments. These Adjust Small

Movements Between Individual Vertebrae,While Movements of the Vertebral Column

Probably Are Performed by Muscles With

Better Leverage and Mechanical Advantage(for Details, See Donisch and Basmajian,

1972).

Normative Data


84/86

Cram and Also Matheson

Have Accumulated

Normative Data for Non-pain Patients but One Must

Be Extremely Careful

Relying on This Data.

Both Studies Used the

Narrow Band Equipment.Wider Frequency Filters Will

Detect More EMG Signal,

and Therefore Readings Will

Vary.

The "Normal Range" Is Very

Broad.

Cram's Data Has Come

Under Scrutiny for Statistical

Error.

Finally Meeker and Others

Have Been Unable to Detect

Differences Between Pain

and Non-pain Controls UsingThis Data.

Most Manufacturers and

Distributors Readily Admit

to the Problem WithNormative Data, but Speak

of Side to Side Asymmetries.

As Noted Above, Not

Enough Is Known About

Complex Acting IntrinsicBack Muscles to Know What

Degree of Asymmetry Is

Normal.

Recently, Some Very ImpressiveSt di S ifi ll Sih d


85/86

Studies, Specifically Sihvonen and

Coworkers From Finland, and Arena and

Co-workers in Augusta Georgia, HaveHad Success in Differentiating Back Pain

Patients From Non-pain Controls. Arena

States That Disk Patients Had the MostSignificant Findings, and Urges for

Diagnostic Categorization of Patients for

Future Studies. It Is Proposed That the

Lack of Diagnostic Criteria Is

Responsible for the Contradictory

Findings of Earlier Investigators.


86/86

Conclusions

"Electromyography Has a Great Deal ofPractical Value in This Area And, Aside

From Some General-but ImportantObservations Recorded Above, MuchRemains to Be Learned by ThisTechnique, Especially About the Fine

Functioning of Various Areas and Depthsof the Intrinsic Muscles of the Back".

Basmajian and Deluca

surface electrode emg

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