volitional potentials Flashcards
exp Electromyographic (EMG) Biofeedback
Monitoring, detection, or assessment of skeletal muscle activity - to know if inc (hypotonic) or dec (hypertonic)
what does EMG detect
no current delivered kc voluntary contraction - records upon contraction of muscle
exp facilitatory biofeedback
inc muscle activity (post-injury or post-operatively) - hypotonic or flaccid
Normalize muscle functions
Improve volitional motor control following CNS dysfunction
exp inhibitory biofeedback
dec muscle activity (spasticity in CNS dysfunctions)
dec muscle activity (due to postural stress)
dec muscle activity/guarding (due to chronic pain)
instrument used for EMG biofeedback
electromyograph
discuss recording electrode placement
over muscle to be recorded - proper spacing and avoid crosstalk
discuss ground electrode placement
over bony surface to minimize extraneous electrical activity or nosie
compare surface EMG and needle EMG
sEMG - non invasive; superficial
nEMG - invasive; deep
uses of biofeedback
training technique to gain voluntary control over muscular or autonomic nervous system functions using auditory or visual stimuli
purpose of signal amplification and filtration
maximize signal-noise ratio and minimize distortion
noise sources during EMG
noise of electrical parts in machine
ambient noise
motion artefacts bet electrode and skin
inherent instab of EMG signal d/t random firing of motor units
compare high and low pass filter
high - allows high freq; 5 Hz/10-20 Hz cut-off
low - allows low freq; 500 Hz cut-off
what is linear envelop
rectification + low pass filter
what is butterworth or chebyshev
traditional low-pass filter of rectified signal
what is Movag
certain amount of data are averaged using the
sliding window technique
what is RMS
preferred method
based on square root calculation - reflects mean power of signal
normal muscle fatigue index of EMG at rest
(+) insertion activity
miniature endplate action
potentials
no muscle action potentials
abnormal muscle fatigue index of EMG at rest
(+) fibrillations / fasciculations
complex discharges
inc or dec insertional activity
normal muscle fatigue index of EMG at mild contraction
biphasic or triphasic muscle AP
motor unit potentials (MUP) from small amplitude potentials → progressively large amplitude potentials
abnormal muscle fatigue index of EMG at mild contraction
polyphasic amplitude tas either increase or decrease
altered recruitment patterns
normal muscle fatigue index of EMG at max contraction
inc frequency
(N) stepwise - inc interference patterns
abnormal muscle fatigue index of EMG at max contraction
dec interference pattern - hypo
early full interference pattern - hyper
guidelines for all electrophysiologic testing
Patient should be comfortable
Ensure correct electrode placement
Secure electrodes properly
Perform first a detailed physical examination of
strength, sensation, coordination, reflexes and
other neuromuscular function
Use latex gloves, goggles and gown for needle
EMG
When applying electrical stimulation, check for
contraindications and precautions
