NMES Flashcards
What is NMES?
Any ES that produces a muscle contraction
What is arthogenic muscle inhibition (AMI)?
When the ability to recruit strong coordinated ms contractions is compromised by joint injury
Injury results in pain, swelling, and altered mechanoreceptor input
Impaired neuromuscular control following injury with decreased ability to perform volitional muscle contraction
What is a volitional ms contraction?
Actively making a ms contract
T/f: neuromuscular inhibition persists as long as the joint capsule volume remains elevated
True
Capsular swelling may stimulate _____ receptors and trigger reflex inhibition
Stretch
Why is it important to get swelling down?
Bc it can cause AMI causing neuromuscular inhibition
How many mL of fluid does it take to inhibit VMO fxn
30 mL (~2tsp)
When there is ____ mL of fluid in a joint causing swelling it can severely limit ability to SLR
200
T/f: pain contributes to deficits in neuromuscular control
True
T/f: AMI results in altered input that changes the pattern of sensory input from mechanoreceptors decreasing neuromuscular control
True
What are the intrinsic changes from AMI?
Muscle fiber atrophy and fiber loss
What are the extrinsic changes in AMI?
Impaired motor unit recruitments in regard to size, #, frequency, and synchronization
Following a TKA, during the initial weeks post-op, what is responsible for the decline in strength?
Neural impairment
Over time, following a TKA, decline in strength is due to what?
Intrinsic loss (loss of ms mass)
Post-op TKA, when are the benefits of NMES most evident?
During the initial period when motor unit recruitment is most impaired
How does NMES work for intact motor nerves?
It induced a ms contraction by stimulating the alpha motor nerve and the entire motor unit associated with the nerve will respond
How does NMES work with a denervated muscle?
It induces a ms contraction by depolarizing the sarcolemma in a denervated ms where the peripheral nerve is no longer in tact
In voluntary motor contractions, how are muscle fibers recruited?
From small to large according to the intensity of the contraction
Does voluntary muscle involve synchronous or asynchronous firing?
Asynchronous firing
Why do muscle fibers fire asynchronously in voluntary muscle contractions?
To promote continuous contraction and reduce fatigue
T/f: there is GTO inhibition with strong voluntary muscle contractions
True
When a denervated muscle is stimulated with NMES, it is not called NMES, what is it called?
EMS
When NMES induces muscle contractions, how are muscle fibers recruited?
Fibers are randomly recruited and spatially fixed
Do muscle fibers contract synchronously or asynchronously with NMES?
Synchronously
T/f: muscles can fatigue quickly with NMES bc of the synchronous firing
True
What are the small muscle fibers?
Slow twitch fibers
Tonic fibers
Type 1 fibers
What are large twitch fibers?
Fast twitch fibers
Phasic fibers
Type 2 fibers
In the quads, where are most small muscle fibers located?
In the depth of the muscle
In the quads, where are most large muscle fibers located?
On the surface of the muscle
Muscle fiber recruitment through ES depends on what?
Current density
What fibers are mainly recruited by NMES?
Muscle fibers located directly beneath the ES electrodes
Current density _____ with increasing depth of the muscle
Decreases
T/f: muscle fibers are recruited from surface to depth of the muscle with NMES
True
T/f: evidence has shown that using ES post op leads to slower gains than those who did not use ES
False, ES leads to quicker gains
In a healthy muscle, to produce strength gains with NMES, the force of contractions needs to be at least ____% MVIC
50
How do we determine a pts MVIC?
Using dynamometry (handheld or Biodex) have the pt make as a strong of a contraction as they possibly can
With an impaired or post op pt, to produce strength gains with NMES, we can start with contractions as little as ___% MIVC
10
When would we use 10% MVIC with NMES?
During day one post op when they are in a lot of pain and can’t contract very much
T/f: NMES can be very beneficial to pts that can’t volitionally contract their muscles
True
Once good volitional contractions are achieved with NMES, what should we do?
Discontinue NMES
Isometric strength gains are _____ ______
Position specific
T/f: NMES is more effective than resistance training throughout the normal ROM in a healthy person
False
T/f: NMES is used clinically to strengthen weakened muscles in persons with MSK disorders and is supported by evidence
True
Muscle strengthening is the result of what two mechanisms?
Increased muscle mass
Increased motor unit recruitment
How long does it take for muscle strengthening from increase muscle mass to occur?
Generally 6-8 weeks
How long does it take to strengthen a muscle through increased motor unit recruitment?
Not long at all, it happens rapidly
How is motor unit recruitment increased with muscle strengthening with NMES?
Through an increased # of motor units recruited, an increased frequency of motor unit recruitment, and recruitment in a synchronized manner
T/f: some studies have shown that there is reduced muscle atrophy and greater preserved contractility of muscles down the road with NMES
True
T/f: some research suggests that 2 forms of ES can be summarize and yield a greater MVIC
True
How can we get the best results from NMES?
By using active muscle contractions with it while having the pt watch the contractions
What is the waveform of NMES?
Symmetrical or asymmetrical biphasic pulsed current
Burst modulated alternating current (Russian)
What is the current form of Russian stim?
Sinusoidal AC current
What is the carrier frequency of Russian stim?
2500Hz
What is the phase duration of Russian stim?
400usec
What is the burst modulation on Russian stim?
10ms on 10ms off
What is the frequency of Russian stim?
50 hz
What is the extrinsic duty cycle of Russian stim?
Initially set to 10s on 50s off
What is the pulse duration and amplitude for enchanting muscle strength with NMES?
Highest pulse duration and a,plotted tolerated by the pt should be used
What is the frequency used to enhance muscle strength with NMES?
Generally over 30pps (50pps recommended)
Increased frequency leads to ____ force generation
Increased
When we use too much frequency with NMES, what occurs?
Tetany and the muscle shuts down
In general, what frequency should we use on NMES for the UEs (smaller ms groups)?
30-40pps
In general, what frequency should we use on NMES for the LEs (larger ms groups)?
40-50pps
Frequency above ____pps causes tenant beyond fxn
80
What are typical parameters for muscle strengthening with NMES given from the textbook?
Waveform: symmetrical or asymmetrical biphasic pulsed current, burst modulated AC (Russian)
Pulse duration: 200-600usec
Frequency: 20-100pps
Amplitude: at least 50% MVIC
Ramp up time: 1-5s
Ramp down time: 1-2s
Duty cycle: 1:3, to 1:5 with up to 10s on, 50s off
Treatment time/duration: at least 10 contractions or up to 1hr/day 3-5x/week for 4-8 weeks
What is the typical pulse width of FES?
400usec
What is the typical frequency of FES?
30pps then increase to counter ms fatigue
What is the typical intensity of FES?
Enough to complete a fxnal task
What is the typical in/off time for FES?
Activity dependent
What is the typical ramp time for FES?
Activity dependent
What is the typical treatment time for FES?
Activity dependent
Larger muscle groups use a ____ramp, and smaller muscle groups use a ____ ramp but it’s generally not suggested to go over 2 seconds
Longer, shorter
What is synchronous NMES?
Both channels contract and relax at the same time for max power on a large muscle groups
What is alternating NMES?
Both channels on but alternates in contraction and relaxation used for opposing muscle groups
What are the indications for NMES?
Enhance muscle contraction
Strengthen for correct muscle use
Re-education after muscle transfer
ROM
Increase blood flow
Scoliosis in conjunction with brace
Fxnal activities
Hemishoulder subluxation
T/f: NMES leads to a reduced loss of muscle CSA
True
T/f: NMES in conjunction with exercise improves quads strength in fewer sessions
True
T/f: NMES has no effect on loss of quads strength
False, it decreased the loss of quads strength
T/f: NMES can prevent and reduce shoulder subluxation
True
For articles that support the use of NMES for scoliosis, how is ES used?
ES electrodes on the convexity of the curve to improve the Cobb angle, gross motor fxn, and trunk balance
What is the difference bw NMES and TENS?
NMES is mostly for muscle contraction
TENS is more sensory/motor stim for pain reduction
Why might NMES cause long term analgesic effects in hemiplegia shoulder pain but not ROM, ADLs, etc in a research article?
Possibly bc the NMES induced muscle contraction gets the humeral head in place to get pressure off of the brachial plexus but the firing doesn’t necessarily lead to increased functioning
T/f: an article found that NMES can be used to decrease mechanical ventilator time in the ICU
True
The ability to produce a contraction with NMES is influenced by what factors?
Past experiences (fear avoidance)
Pain
Cultural experiences
Superimposition of _____ and _____ can theoretically activate more motor units than volitional contraction alone
ES, volitional contraction
Volitional eccentric contractions are limited by what?
Neural inhibition?
What can we use to try and decrease the neural inhibition of volitional eccentric contractions?
Use ES with volitional eccentric contraction
How does the use of ES with volitional eccentric contraction help with muscle contraction
ES stimulates cutaneous receptors to decrease neural inhibition and increase motor unit recruitment to increase force production
What are some factors to consider when applying NMES?
Line or battery powered stimulator
Stimulation parameters
Electrode placement
On and off times
Dosage (intensity)
# of reps/sets
Frequency of application
What is the most important NMES parameter?
Amplitude
What is the amplitude used with NMES?
Near max tolerance required for increasing strength (near 70% MVIC is common)
How should electrodes be arranged for NMES?
The electrodes should be arranged to recruit as many motor units as possible by placing electrodes on motor points
Can be mono, bi, or quadripolar
T/f: current density is inversely proportional to electrode area
True
If the electrode used is too small, what happens to the current density? What will the pt feel?
It is increased and can be uncomfortable to the pt
If large electrodes are not available to use, what should we do?
Use 2 channels or bi-frucate the active lead
What are motor points?
The location where the motor nerve enters the muscle
The point of least resistance to achieve muscle contraction
Most electrically excitable location of a muscle
What is the most electrically excitable location on a muscle?
The motor points
How can we identify motor points?
Using a motor point map as a guideline
Or using ES probing
If electrodes are too far apart, what is the result?
The stim gets too deep and can get to the opposite muscle group
If electrodes are too close together, what is the result?
The current is not dispersed and can be uncomfortable
What is the most important muscle to stimulate to prevent downward shoulder subluxation?
Supraspinatus
What is the risk with using a cold pack before NMES?
It may elevate the electrical sensory threshold via a numbing effect leading to a need for increased intensity to get the same result
BURN RISK
What is the risk of using a hot pack before NMES?
It may reduce the current tolerance and may preclude reaching the required current intensity needed for strengthening
Does US alter the electrical sensory threshold and current tolerance level for NMES?
Nope
What is muscle atrophy?
Significant decrease in muscle mass and fiber size within one week
Atrophy of what muscle puts pts at increased fall risk?
Ant tib
What happens to muscle tissue capillary supply with muscle atrophy?
It is reduced
What happens to capillary-to-fiber ratio with muscle atrophy?
It is reduced
What happens to capillary diameter with muscle atrophy?
It is reduced
T/f: ES of denervated muscles is effective in retarding denervated muscle atrophy
True
How does ES of denervated muscles slow denervated muscle atrophy?
By increasing muscle mass and increasing the average muscle fiber diameter
T/f: some research has shown that there may be adverse effects on nerve regeneration with use of ES on denervated muscles
True
What are theorized adverse effects on nerve regeneration with use of ES on denervated muscle?
Adverse effects on regeneration of nerve terminals in the neuromuscular junction
Adverse effects on the membrane system involved in excitation-contraction coupling
T/f: the use of ES for muscle denervation is controversial with mixed messages in the literature about its effects on nerve regeneration
True
What waveform is typically used for NMES of denervated muscles?
DC/monophasic
What pulse duration is typically used for NMES of denervated muscles?
> 1msec
What frequency is typically used for NMES of denervated muscles?
Low (2-4 pps) or higher (20-40pps)
ES for muscle denervation is most commonly used for what?
Facial nerve palsy in Bells Palsy
What is the big concern with Bells Palsy?
The pts can’t get their eye to close so it can dry out and lead to corneal abrasions
What is the typical waveform for using NMES to stimulate denervated muscles?
Monophasic/DC
What is the typical pulse duration for using NMES to stimulate denervated muscles?
1-450 msec (long)
What is the typical frequency for using NMES to stimulate denervated muscles?
1-500 pps
What is the typical amplitude for using NMES to stimulate denervated muscles?
To obtain contraction but low to prevent burns
What is the typical ramp amplitude for using NMES to stimulate denervated muscles?
Not identified
What is the typical duty cycle for using NMES to stimulate denervated muscles?
Highly variable, 30min-8 hrs per day
What is the typical treatment time/duration for using NMES to stimulate denervated muscles?
5-7 days/week, 4 days to 4 years
What are the goals of NMES for stimulating denervated muscles?
Delay atrophy
Prevent contractures
Prevent denervation hypersensitivity
What is the cause of idiopathic facial palsy?
Idiopathic, latent herpes virus which is reactivated in CN ganglia, causes an inflammatory compression injury
What are the treatments for Bell’s palsy?
Meds (steroids, anti-virals)
Moist heat, facial muscle massage, facial expression exercises, US (phonophoresis), ES
Surg
