electro - biofeedback

during EMG, electrical activity is detected by trigger of

action potential (recording of ion movement [electrical charges] as muscle membrane is depolarized)

EMG signal represents

summation of motor unit action potentials

(provides information about muscle activity)no

does EMG measure force?

no (just indicates that motor units are active)

EMG set up

- pair of electrodes to record electrical activity (over target muscle)

- another electrode (reference or ground)

amplitude of the EMG BFB signal is dependent on

- size of motor units

- number of active motor units

- interelectrode distance

electrical activity can be increased by

- activating more motor units (small to large)

- increasing rate at which those motor units that are activated fire

**EMG magnitude increases for the same reasons

narrow vs wider spacing for electrodes

narrow:

- EMG less

- more specificity

- less "crosstalk"

wider:

- higher amp (because getting more motor units)

- more susceptible to cross talk and "noise"

where should you place reference electrode?

- on neutral tissue (bony prominence)

- over muscle not related to tatget muscle

is narrow or wider spacing better for people with very little muscle activation?

wider (higher amplitude)

what is "noise" during EMG

high frequency noise from electronics (laptop, cell phone, etc)

what is the job of the ground/reference electrode?

filtering (getting rid of other stuff to leave "real" EMG)

if your goal is increased activation where do you set the threshold to?

above muscle contraction (set above MVIC)

if your goal is relaxation of one muscle during activation of another where do you set threshold

set is so tone sounds when EMG exceeds desired level (want to keep machine quiet)

t/f: you can compare the strength of contractions of different muscles during EMG

false - large and small muscles can give same EMG amplitude

patient selection for EMG

- pt must have potential for voluntary control

- must be motivated and cognitively aware

indications for EMG

- muscle relaxation (tension HA, TMJ pain)

- muscle recruitment/motor re-ed (inhibition post-surgical)

- incontinence (pelvic floor muscle training)

EMG precautions

- skin irritation

- lack pt receptiveness/motivation

- decreased vision and/or hearing

- no detectable muscle activty