quiz #1 – neuromuscular electrical stimulation
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what are the purposes of neuromuscular electrical stimulation
- strengthen muscles– primary reason
- improve voluntary control of muscles
- relax muscles
- prevent loss of strength of muscles
- realign skeleton– scoliosis
- increase range of motion
Where is the cathode usually placed?
Over the motor point or peripheral nerve
Where is the anode placed?
on the muscle
The anode is also called the _______?
positive or inactive electrode
Will a bigger electrode be stronger?
No, because the voltage would be carried over greater distance
true or false – two or more cathodes will produce a more complex and natural motion.
true or false – the anode is typically smaller or equal to the size of the cathode
false – the cathode is typically smaller or equal to the size of the anode
true or false – the anode is also called the "ground"
name that set up
Name that set up
monopolar set up
What are the parameters of stimulation?
pulse width – ?
- pulse width - 200 – 500 µs
- waveform – variable
- amplitude – depends on tissue resistance
- frequency – 20 – 80 Hz
What are some factors of electrical resistance when performing electrical stimulation
- thick skin – men tend to have thicker skin
- hair – good idea to have electric shaver ( just in case)
how will the type of muscle effect the speed of muscle contraction
- fast twitch will twitch quicker (ex. hand muscles)
- slow twitch will twitch slower (ex. postural muscles)
Do you want to recruit all motor units at once?
No that will cause quicker fatigue
what is critical fusion frequency?
- stimulus frequency at which maximum twitch tension of a single motor unit summates with the maximum twitch tension of a second twitch of the same motor unit
- point at which there is a smooth muscle contraction
What does this graph represent?
- Critical Fusion Frequency
- x-axis: time
- y-axis: tension
- graph shows increased frequency which "pulls the slack out of the muscle"
Define Tetanic contraction
state of tension produced when the critical fusion frequency produces contraction of a single motor unit
What does NMES stand for?
neuromuscular electrical stimulation
true or false – if the frequency is too high the muscle will become fatigued
true or false – small motor units are recruited last
false – small units are recruited first
what are the characteristics of voluntary recruitment of motor units
- smallest units recruited first
- large units recruited last
- units driven at their critical fusion frequency
- never recruit all motor units simultaneously – you have to teach the muscles to do that, Olympic weightlifters
What muscles have the higher critical fusion frequency- hand muscles or postural muscles
- hand muscles = 50 HZ
- postural muscles = 25 HZ
true or false – the thinner/smaller the axons the higher the voltage needed to depolarize the nerve
true because there will be more resistance
true or false – the larger axon the more motor fiber will be innervated
what is the difference between depolarization of motor nerves from electrical stimulation and depolarization of motor nerves from the brain
- electrical stimulation – recruits larger nerves first
- brain – recruits smaller nerves first
what are the characteristics of stimulus evoked contraction
- larger units recruited first
- single twitches occur at stimilus frequencies less than CFF of motor units
- increase in stimulus intensity will recruit more units
- all motor units can be recruited simultaneously
which can produce the greatest tension possible from a skeletal muscle ?
functional electrical stimulation
functional electrical stimulation
what is "ramp"
- a feature on electrical stimulators that will gradually increase or decrease voltage
what is a duty cycle?
- a ratio of on/off time
- 1/3 – strengthening protocol (to avoid muscle cramps)
- grade of 3 will be tolerated by most people
what is the "synchronous" feature on the functional electrical stimulator
two channels on a unit working together
what is the "reciprocal" feature on functional electrical stimulator
have 1 muscle retract while agonist contracts
what is the typical pulse duration
What is the frequency used for most muscles?
What are two potential pulse shapes
What would you like to do?
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