emg biofeedback

EMG-bio feed back

An electromyography – is a clinical technique that involves recording of the electrical activity generated in a muscle (muscle AP) for diagnostic purposes

An electromyogram - is a graphic representation of those electrical currents associated with muscle action

It is a method of controlling a system by reinserting into it the results of its past performance.

-wiener1948

‘A technique which enables the individual to readily determine the activity levels of a particular physiological process, and with appropriate training, learn to manipulate the same process by an internalized mechanism.’

“Operant conditioning learning”

Positive feed backNegative feed back

Electromyographic Measures electrical

activity in skeletal muscle

Peripheral Temperature Measures temperature

changes in distal extremities

Increased temperature indicates a relaxed state

Decreased temperature indicates stress, fear, or anxiety

Photophlethysmography Measures the amount of

light reflected by subcutaneous tissue based on the amount of blood flow

Galvanic skin response Measures electrical

resistance in the skin Moist skin conducts a

current better than dry skin

© 2004

Chance to make appropriate small changes in performance

Eventually larger changes or improvements in performance can be accomplished

The goal is to train the patient to perceive these changes without the use of the measuring instrument so that he or she can practice independently

ADVANTAGES

Biofeedback instruments may use the following signals/devices/sources

Eg: Temperature- Temperature- thermometer-skinthermometer-skin

Type What's Measured Basic method Used For

Brain waveEEG Electrical activity in the brain

Sensors placed on scalp

Alcohol and drug addition, brain damage, epilepsy, hyperactivity, insomnia

Breathing Breath rate, rhythm, volume, and location

Sensors around chest and abdomen or around mouth and nose

Anxiety, asthma, hyperventilation

Electro dermal response

Sweat gland activity Sensors placed on the muscle group in question

Anxiety, overactive sweat glands

Electro-myography

Muscle spasms and tension

May help treat rheumatoid arthritis, premenstrual syndrome, menstrual cramps, and menopausal symptoms

Incontinence, muscle pain, physical rehabilitation, stress, teeth grinding (TMJ), tension headaches, torticollis ("wry neck")

Finger Pulse Pulse rate and amount of blood in each pulse (the higher these are, the more wired your autonomic nervous system is)

Sensor attached to a finger

Anxiety, irregular heartbeat, hypertension

Skin temperature (also called thermal biofeedback)

Blood flow changes (the more blood flows, the warmer the skin)

Temperature sensor (thermistor) taped to finger

Anxiety, hypertension, migraines, Raynaud's disease

1.Providing feed backAppropriateProportionalSensitivity and specificity of

equipmentAppropriate methodTime/scheduled feed back

2.User control Over the method

3.Proper starting position4.Shaping behaviorAvoid fatigue Initial success Set upper and lower threshold Change goals

It is a therapeutic procedure that uses electronic or electromechanical instruments to accurately measure, process, and feed back reinforcing information via auditory or visual signals.

In clinical practice, it is used to help the patient develop greater voluntary control in terms of either neuromuscular relaxation or muscle reeducation following injury.

© 2004

Identify SignalIdentify SignalGet the eletromyographic signal from the Get the eletromyographic signal from the bodybody

Amplify SignalAmplify SignalFilter out background noiseFilter out background noiseSimilar to a volume control on a radio, Similar to a volume control on a radio, enhance the strength of the signal to enhance the strength of the signal to meaningful levelsmeaningful levels

Rectify SignalRectify SignalMake all values “positive”Make all values “positive”

Integrate SignalIntegrate SignalGroup the data into meaningful Group the data into meaningful clustersclusters

Muscle reeducationRegaining neuromuscular control Increasing isometric and isotonic

strength of a muscleRelaxation of muscle spasmDecreasing muscle guardingPain reductionPsychologic relaxation

Measuring muscle activitySeparation / filterationElectrodesDisplaying the feedback

Biofeedback Measures electrical activity of muscle, not muscle contraction.

Gives information about the quality of a muscle contraction

Does not measure the strength of that muscle contraction specifically.

Basic units have one channel composed of three surface electrodes on a self-adhesive electrode

© 2004

“Active” Electrodes Detect electrical signal

“Reference” Electrode Filters nonmeaningful information

electrical energy received through an electrode

separated or filtered from other extraneous electrical activity on

the skin

amplifies the electrical energy

then converted to information that has meaning to the user

• Noise must be eliminated• Noise – by power lines , motor , lights ,

appliances.• Accomplished by using 2 active electrodes and a

single ground/reference electrode differential amplifier CMRR-common mode rejection ratio

• Filters are also used• Use :

Mask true electrical activity Decrease the reliability of the information being

generated

After filtering, signal indicates true muscle activity – “raw” activity

Raw activity – alternating voltageBiofeedback measures the overall

increase and decrease in electrical activity

To obtain this rectification is doneRectified signal can smoothed and

integrated

Skin preparation Application of electrodes Selection of output modes Selection of sensitivity settings Comfortable positioning of the patient Begin with easy task Teach the patient how to use the unit Brief explanation Demonstration

Skin preparation Reduce skin impedance

Positioning of electrodes Placed as near to the muscle being

monitored to minimize noise Parallel to the muscle fibers

Spacing between electrodes More the distance between the electrodes –

will include signal from nearby muscles Types

Surface electrodes Needle electrodes

Made of stainless steel or nickel plated brass kept in a plastic holder

Size : 4mm in diameter – small muscle activity

12.5mm –for large muscle groups

Increase in size will not increase the amplitude of the signal

Conducting gel/paste/cream with high salt content is used

Can be disposable and non-disposable

MONOPOLAR NEEDLE

CONCENTRIC NEEDLE

BIPOLAR CONCENTRIC NEEDLE

Visual feedbackAudio feedback

▪Line travelling across a monitor

▪Light/series of light that goes on and off

▪Bar graph▪ Incorporated video games

▪Tone▪Buzzing▪Beeping▪Clicking

An Increase increased electrical activity used to strengthen muscle contractions

Decrease decreased electrical activity used for relaxation

Goal is to reestablish neuromuscular control

Used to regain normal agonist/antagonist muscle action

For postural control retrainingUseful in patients who perform

poorly on manual muscle testsBalance/mobility

Muscle guarding Muscle guarding different from muscle

spasticity Goal : to induce relaxation or to

modulate pain by reducing electrical activity

Patient attempts to reduce visual/auditory feedback to zero

Positioning is important Verbal cues should be given to

enhance relaxation

Purpose : reduce/modulate painBreaking “pain-guarding-pain” cycleReduces pain in headaches and low

back painTechniques of imagery and

progressive relaxation is used

HemiplegiaStrokeSpinal cord injurySpasticityCerebral palsyFacial paralysisUrinary and fecal incontinence

HTNStress Reynaud's diseaseRespiratory control

severe psychosisdepressionpsychopathic personalities diabetics and others with endocrine

disordersAny musculoskeletal condition in

which a muscular contraction might exaggerate that condition