EMG biofeedback

Question 1

EMG biofeedback description

Answer 1

• The therapeutic use of instrumentation to detect and feed back electric signals from motor unit APs (MUAP) that are generated by active muscle
• these devices do not actually measure direct physiological events
• the biofeedback unit records some aspect that is highly correlated with actual physiological events
• examples of correlated aspects
• peripheral skin temp
• finger photo transmission
• electromyographic activity

Question 2

Motor unit Action potentials (MUAP)

Answer 2

These MUAP signals are detected, amplified, rectified, filtered, integrated, and converted into audiovisual signals that are used to reinforce voluntary muscle control

• relax hyperactive muscle
• increases recruitment of hypoactive muscles

Question 3

Electromyographic activity

Answer 3

• muscle contraction results from depolarization of muscle fiber due to binding of NT (acetylcholine) from the alpha motor neuron to receptor sites at neuromuscular junction
• depolarization results in increased permeability of muscle membrane to potassium and sodium
• this changes concentration of these ions in extracellular fluid
• can be detected by surface electrodes connected to very sensitive voltage measuring device
• EMG measures this voltage change

Question 4

Electromyographic activity: changes detected by?

Answer 4

changes in electrochemical gradient created by the MUAP can be detected by an electrode

Question 5

Electromyographic activity: motor recruitment

Answer 5

• As more motor units are recruited, muscle tension increases and more electrical energy is detected by the EMG electrode
• smaller motor units are recruited first
• faster contractions tend to excite larger motor units & depress smaller ones
• the firing rate and recruitment of motor units is dependent upon external force required to perform task successfully

Question 6

Electromyographic activity: EMG amplitude effects

Answer 6

• size of motor unit
• number of active motor units
• distance of active muscle fibers from recording electrode
• size of recording area
• inteletrode spacing
• *EMG has near linear relationship with force produced during carefully controlled isometric contractions
• • linear relationship does NOT hold true for concentric or eccentric contractions

Question 7

EMG biofeedback purpose

Answer 7

• To change MUAPs into auditory and/or visual cues for the purpose of increasing or decreasing voluntary muscle activity
• to enhanced motor learning by providing feedback about performance until motor skills develop sufficiently so that feedback is no longer needed

Question 8

EMG biofeedback advantages

Answer 8

• provides immediate reward for performance changes that may be too small to note without EMG-B
• these small changes often lead to larger changes in performance improvment
• pt is able to obtain feedback about performance without the constant supervision of the therapist

Question 9

EMG biofeedback indications

Answer 9

Motor recruitment
- when the goal is to increase the EMG signal from the target muscle
Motor inhibition
- when the goal is to decrease the EMG signal from the target muscle
Total body relaxation
- conditions of generalized pain or stress where the goal is to decrease undesirable muscle tension to achieve muscle relaxation and stress reduction

Question 10

EMG biofeedback contraindications

Answer 10

any condition where a muscle contraction might exacerbate the condition

Question 11

EMG biofeedback safe and effective application

Answer 11

• Obtain informed consent
• select the appropriate muscle or muscle group needed to achieve the therapeutic goal
• Prepare the skin by cleaning with alcohol
• determine the appropriate electrode placement
• place the active electrodes over the muscle belly of the target muscle
• ensure that the active electrodes are parallel to the muscle fibers
• place the ground electrode over a bony prominenece or non contractile tissue
• set the appropriate gain/sensitivity and threshold/goal on the EMG-B unit per therapeutic goal
• remove electrodes and clean skin of any adhesive
• document electrode spacing, progress in gain and threshold settings, positioning toward function, treatment duration, etc