EMG Biofeedback Flashcards
What is EMG biofeedback
The therapeutic use of instrumentation to detect and feedback electric signals from motor unit action potentials (MUAP) that are generated by active muscle
What happens to the MUAP signals
They are detected, amplified, rectified, filtered, intergrated, and converted into audiovisual signals
What are the audiovisual signals used for
Reinforce voluntary muscle control
True or False:
EMG biodfeedback machines measure actual direct physiologic events
False
What does EMG biofeedback actually measure
Some aspect that is highly correlated with an actual physiologic event
What are 3 examples of correlated aspects
- Peripheral skin temperature
- Finger photo transmission
- Electromyography
A muscle contraction is a result of what
Depolarization of muscle fibers due to binding of NT released from the alpha motor neuron
What does the depolarization of the muscle fibers result in
Increased permeability of the muscle membrane to K+ and Na+
What does the change in permeability cause
Changes in the concentration of these ions in the extracellular fluid
How are these changes in concentrations of ions detected
By surface electrodes connected to a very sensitive voltage measuring device
What measures the change in voltage
EMG
What is electromyography activity
Changes in the electrochemical gradient created by the MUAP that is detected by an electrode
What happens as more motor units are recruited
Muscle tension increases and more electrical activity is detected by the EMG electrode
What size motor units are recruited first
Small motor units
What do faster contractions tend to do
Excite larger motor units and depress smaller ones
What is the firing rate and recruitment of motor units dependent on
The external force required to perform a task successfully
What does the amplitude of the EMG reflect (5)
- Size of motor units
- Number of active motor units
- Distance of active muscle fibers from recording electrode
- Size of recording area
- Interelectrode spacing
True or False:
EMG has near linear relationship with force produced during carefully controlled isometric contractions
True
Does the linear relationship hold true for concentric or eccentric contractions
Nope
What is electrical activity of a muscle measured in
Micro volts
True or False:
Noise must be eliminated before amplification of the detected MUAP can occur
True
What can noise be defined as
Extraneous electrical activity that may be produced by any source other than the contracting muscle
How many electrodes are required to eliminate noise
3
What are the 3 electrodes
2 active electrodes and one reference or ground electrode
Where are the active electrodes placed in relationship to each other
Close to one another
Where is the reference electrode located
Anywhere in the body
What do the active electrodes detect
Electrical activity from the motor units firing in the muscle below them
True or False:
The magnitude of the voltage picked up by each electrode differ with respect to the reference electrode
True
What happens to the 2 resulting signals
The signal from one active electrode is subtracted from the other leaving only the amplified difference in signals
What does the differential amplification do
Significantly decreases extraneous noise
What is the ability of the differential amplifer to eliminate common noise between the two active electrodes called
The common mode rejection ratio (CMRR)
What happens once the signal is amplified
Any remaining noise in the resultant signal is filtered
What is the resulting amplified and filtered signal known as
Raw activity
What is the raw activity defined as
An alternating voltage representative of the true electrical activity in the muscle being monitored
True or False:
EMG-B units measure the overall increase and decrease in electrical activity so the raw activity must be rectified
True
How is the raw activity rectified
By flipping all of the negatively deflected signals upward toward the positive pole
What happens after the signal is rectified
It is smoothed and intergrated
What is the purpose of EMG-B (2)
- Change MUAPs into auditory and/or visual cues for the purpose of increasing or decreasing voluntary muscle activity
- To enhance motor learning by providing feedback about performance until motor skills develop sufficiently so that feed back is no longer needed
What are the advantages of EMG-B (3)
- Provides immediate reward for performance changes that may be too small to note without EMG-B
- The small changes seen by EMG-B often lead to larger changes in performance improvement
- Patient is able to obtain feedback about performance without the constant supervision of the therapist
What are the indications for EMG-B for motor recruitment
When the goal is to increase the EMG signal from the target muscle
What are the indications for EMG-B for motor inhibition
When the goal is to decrease the EMG signal from the target muscle
What are the indications for EMG-B for 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
What is an example of when you would use EMG-B to increase the EMG signal from the target muscle
A muscle that is hypoactive
What is an example of when you would use EMG-B to decrease the EMG signal from the target muscle
A muscle that is hyperactive
What are the contraindications of EMG-B
Any condition where muscular contraction might exacerbate the condition
When using EMG-B how must you clean the skin
By using alcohol
True or False:
You want the active electrodes to be parallel to the muscle fibers
True
Where do you put the ground electrode
Over a boney prominence or non contractile tissue
