EMG.pdf

Medical Electronics

1. Electromyogram(EMG)
•Thebioelectricpotentialassociatedwithmuscleactivityconstitutethe
electromyogram(EMG).
•Muscle is organized functionally on the basis of the motorunit.
•Amotorunitisdefinedasonemotorneuronandallofthemusclefibersit
innervates.
•Whenamotorunitfires,theimpulse(actionpotential)iscarrieddownthemotor
neurontothemuscle.Theareawherethenervecontactsthemuscleiscalledthe
neuromuscularjunction,orthemotorendplate.
•Thepotentialsaremeasuredatthesurfaceofthebody,nearamuscleofinterest
or directly from the muscle by penetrating the skin with needleelectrodes.
•EMGpotentialsrangebetweenlessthan50μVandupto20to30mV,depending
onthemuscleunderobservation.
1 N.Mathavan AP - ECE NSCET - Medical Electronics (EC8073)

2. 2 N.Mathavan AP - ECE NSCET - Medical Electronics (EC8073)
Electromyogram(EMG)

3. 3 N.Mathavan AP - ECE NSCET - Medical Electronics (EC8073)

4. Electromyogram(EMG)
•TheEMGpatternisusuallyasummationoftheindividualactionpotentialsfrom
thefibersconsistingthemuscleormusclesbeingmeasured.
•Thesignalscanbeanalyzedtodetectmedicalabnormalities,activationlevel,
recruitment order or to analyze the biomechanics of human or animalmovement.
•There are two kinds of EMG in widespreaduse:
1.SurfaceEMG
2.Intramuscular (needle and fine-wire)EMG.
A needle electrode or a needle containing two fine-wire electrodes is insertedthrough
the skin into the muscletissue.
•Abnormal spontaneous activity might indicate some nerve and/or muscledamage
•The shape, size, and frequency of the resulting motor unit potentials areanalyzed.
•Thecompositionofthemotorunit,thenumberofmusclefibrespermotorunit,
themetabolictypeofmusclefibresandmanyotherfactorsaffecttheshapeofthe
motorunitpotentialsinthemyogram.
4 N.Mathavan AP - ECE NSCET - Medical Electronics (EC8073)

5. 5 N.Mathavan AP - ECE NSCET - Medical Electronics (EC8073)
Electromyogram(EMG)

6. Electromyogram(EMG)
6 N.Mathavan AP - ECE NSCET - Medical Electronics (EC8073)

7. EMGApplications
•EMGisusedasadiagnosticstoolfor
identifying:
•Neuromuscular diseases, assessing low-
backpain
•Disorders of motorcontrol.
•EMGsignalsarealsousedas:
•Acontrolsignalforprostheticdevices
suchasprosthetichands,arms,and
lowerlimbs.
•Tosenseisometricmuscularactivity
wherenomovementisproduced.And
canbeused:
•Tocontrolinterfaceswithoutbeing
noticedandwithoutdisruptingthe
surroundingenvironment.
•Tocontrolanelectronicdevice
such as a mobile phone orPDA.
7 N.Mathavan AP - ECE NSCET - Medical Electronics (EC8073)

8. Electromyogram(EMG)
•EMG signals have been targeted as control for flightsystems.
•TheHumanSensesGroupattheNASAResearchCenteratMoffettField,CAseeks
toadvanceman-machineinterfacesbydirectlyconnectingapersontoacomputer.
•An EMG signal is used to substitute for mechanical joysticks andkeyboards.
•EMGhasalsobeenusedinresearchtowardsa"wearablecockpit,"whichemploys
EMG-basedgesturestomanipulateswitchesandcontrolsticksnecessaryforflight
inconjunctionwithagoggle-baseddisp
lay.
8 N.Mathavan AP - ECE NSCET - Medical Electronics (EC8073)