electromyographic feedback (biofeedback)

decreased peripheral temperature

indicates stress, fear, anxiety

EMG

most commonly used form of biofeedback

biofeedback scale and measurement

can be both visual and audio, measured in microvolts, 0-10 scale, or some form of pitch

finger phototransmission

measured indirectly using a photoplethysmograph

monitors amt of light reflected by subcutaneous tissues based on amt of blood flow

as blood volume increases→amount of light detected decreases

galvanic skin response

measures amt of perspiration on the skin—sweat contains salt→incr conductivity

passes a small current through fingers (volar surface) and/or palm

measures impedance of electrical current

used for lie detector testing

biofeedback electrode placement

placement from day to day affects magnitude reached on biofeedback scale

ex. directly over a motor point (ideal) on 1 day and next to a motor point the next

2 active electrodes (measure electrical activity), 1 reference electrode (filters noise)

muscle re-education indications

s/p surgery or long-term immobilization

quadriceps following ACL surgery

PFD rehab to reeducate VMO : VL timing patterns (requires 2 channels)

may use along with NMES

relaxation of muscle tension indications

trapezius tension

biofeedback is most effective when?

when implemented early

surface electrodes

monitor electrical activity within a local area of muscle — monitor units increase, electrical activity increase

more sensitive to superficial versus deep muscles

T/F: the activity monitored is a direct measurement of muscular strength

false

how would you accurately monitor deep muscles?

use fine wire (needle) electrodes

active electrodes

detects electrical activity from muscle contraction &converts into visual or auditory signals

reference (ground) electrode

filters “noise”

point of reference to compare the electrical activity recorded by the active electrodes

differential amplifier

receives 2 signals from active electrodes that differ with respect to reference

subtracts one signal from the other and uses reference to compare the signals received from actives→cancels out any components that the signals have in common→amplifies difference btwn signals

common mode rejection ratio

the ability of the differential amplifier to eliminate teh common noise between active electrodes

filtering

reducing external noise, making amplifier sensitive to some incoming frequencies and less sensitive to others

filter noise from high and low frequency sources

muscle activity: 80-250 Hz

electrical current: 60 Hz

amplification of signal processing

raw signal in microvolts, amplify into millivolts

raw EMG activity

true electrical activity in muscle after amplification and filtering

alternating voltage—direction/polarity constantly reversing

rectification

deflection toward negative pole must be flipped upward toward positive pole to determine overall increase and decrease in electrical activity

absolute value of - signal

integration

area under the curve for a specified period of time

total amount of EMG activity occurring during a specified time interval

signal smoothed and area under curve measured→converted into output signal

EMG use indications

facilitation for muscle reeducation

restoration of neuromuscular function

increase muscle strength

promote spasm relaxation

reduction of muscle guarding

assistance w/ pain control

neuro conditions (following stroke, spinal cord injury, cerebral palsy, incontinence)

contraindications of EMG

conditions in which muscular contractures would compromise healing structures

conditions where contraction will cause joint movement and motion is contraindicated

effects of EMG on pain

facilitation of muscle reeducation & promotion of muscle relaxation that may occur with biofeedback training may result in decreased pain

muscle reeducation procedures

1. ensure no contraindications

2. clean treatment site(s)

3. place electrodes over a motor point(s)

4. educate pt regarding purpose

5. establish goals

6. have pt perform a maximum contraction of target m

7. set goal line of biofeedback unit based on performance of maximum contraction

8. instruct pt to perform desired number of contractions and hold each above goal line for specified amount of time

9. goal line can be adjusted as indicated

10. after biofeedback, have pt perform contractions on their own

11. give pt a home program

methods to facilitate muscle contraction

have pt contract contralateral m prior to or along with involved m

let pt practice w/ biofeedback on contralateral m before training involved m

have pt contract surrounding mm w/ target m

begin w/ NMES contractions and transition to biofeedback monitored contractions

lightly touch/tap target m as pt attempts to contract

for quads: towel roll under pt knee, have them push into it as they attempt to contract quads

muscle relaxation procedure goal

decrease number of motor impulses being relayed to muscle in spasm

muscle relaxation procedures

1. set goal line of unit based on baseline level of activity present in target m (often silent at level of baseline, beeps if activity drops below aka m relaxes)

2. instruct pt to concentrate on relaxing target m

3. goal line may be adjusted as indicated

4. give pt a home program

methods to facilitate muscle relaxation

mental imagery or deep breathing techniques

instruct pt to contract target m and concentrate on relaxing as they release contraction

contract opposing m in attempt to elicit reciprocal inhibition

alter body position