Neuromuscular Electrical Stimulation (NEMS)/Biofeedback (WEEK 11) Flashcards Preview

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Flashcards in Neuromuscular Electrical Stimulation (NEMS)/Biofeedback (WEEK 11) Deck (40):
1

What is NMES? Goal?

Electrical current that is delivered to the surface of the skin.

Goal: produce muscle contractions through the stimulation of motor nerves
- retrain inhibited muscles
- strengthen weakened muscles
- oedema control

2

How does NMES work (4 steps)

1. Application of sufficient electrical current will depolarize the motor neurons
2. The signal propagates to the NM junction
3. NT ACh is released by the nerve into the NMJ and binds to the receptor site at the muscle
4. The muscle fiber fires

3

What structure contains ACh?

Axon terminal has vesicles that contains ACh

4

ACh receptor site?

Muscle

5

Treatment Parameters: Intensity

As intensity increases, the number of stimulated MU is increased, resulting in an increase in force generation

6

Treatment parameters: Pulse duration

Recommended:
> 250usec

7

Treatment parameters: Frequency

- low frequency
- ideal/therapeutic frequency

- low frequency (<20Hz): the muscle twitches

- 30-50Hz: titanic contraction (Sustained); just looking for a constant contraction

8

Frequency recommendation:

Lowest frequency needed to get a sustain contraction - replicate functional activity

9

Treatment parameters: increasing frequency and the problem with increasing frequency

- force contraction increases with frequency (increased muscle force production)
**

at high frequency we will get constant contraction of the muscle, we are potentially depleting all the NT not because of meaningful training, rather we are running out of NT
- high frequency brings on fatigue more rapidly which may not be desirable
- Fatigue due NT depletion which has no therapeutic benefit to patient

10

Treatment parameters: Time

- helps to replicate a normal physiological contraction and/or replicate functional movements

11

Time parameters:

1. On time
2. Off time
3. Rise time
4. Fall time

1. On: Determines the duration of muscle contraction (may or may not include rise/fall time)

12

Time Parameters: Off time

1. On: Determines the duration of muscle contraction (may or may not include rise/fall time)

2. Off: Rest time between contractions

3. Ramp (rise): gradual increase in intensity until the desired intensity is reached; avoids the discomfort of a sudden strong contraction

4. Fall: gradual decrease in intensity at the end of contraction

13

Time parameters: Rise (Ramp) Time

1. On: Determines the duration of muscle contraction (may or may not include rise/fall time)

2. Off: Rest time between contractions

3. Ramp (rise): gradual increase in intensity until the desired intensity is reached; avoids the discomfort of a sudden strong contraction

4. Fall: gradual decrease in intensity at the end of contraction

14

Time parameters: Fall time

1. On: Determines the duration of muscle contraction (may or may not include rise/fall time)

2. Off: Rest time between contractions

3. Ramp (rise): gradual increase in intensity until the desired intensity is reached; avoids the discomfort of a sudden strong contraction

4. Fall: gradual decrease in intensity at the end of contraction

15

Common clinical use of NMES

- overdose muscle inhibition post-injury or post-surgery
- Strengthen muscles post -injury, -surgery, or to combat deconditioning
- Control oedema in immobilized limbs (via muscle pumps)

16

Limitations in clinical use of NMES

- electrically stimulated muscles do not produce a normal physiological contraction
- fatigue is an issue
- hard to produce a contraction greater than 20-30% of MVC without sassing too much discomfort; there is a limit to the amount of stimulation that can be applied. (E.g. higher intensity stimulates nocicpetive nerves along with motor nerves - pain threshold)

17

Physiological vs. NMES contraction: recruitment of fast and slow twitch fires

Physiological: slow twitch are recruited first, fast twitch excited with increased force

NMES: non-selective recruitment of fast- and slow- twitch fibers (can’t go from slow —> fast)

18

Physiological vs. NMES: inhibition of alpha-motor neuron

Physiological: strong stimulation of GTO will cause inhibition, preventing excessively strong contraction

NMES: GTO is stimulated but inhibition is prevented due to direct electively stimulation of the motor nerve

19

Physiological vs. NMES contraction: Synchrony of firing

Physiological: smooth (only what is needed is recruited)

NMES: jerky (all or none) effect

20

Physiological vs. NMES: fatigue

Physiological: minimal fatigue (only certain fibers fires, when tired others take over creating a smooth contraction)

NMES: any fibers in path will be stimulated therefore onset of fatigue is fast

21

Muscle fiber recruitment via electrical stimulation

Electrical stims recruit muscle fibers in reverse order of a normal contraction
- fast is recruited before slow due to larger axon size of fast twitch MU
- only true when muscles stimulated with electric current
- NMES non-selective of what fiber type is stimulated (simply stimulates what is in range)

22

Physiological vs. NMES: stimulation of alpha motor neuron and effect on GTO inhibition

how does this relate to pain

Physiological: GTO inhibits AMN from excessive contraction

NMES: No GTO inhibition because AMN stimulated in periphery instead of dorsal root horn
-stimulation of alpha motor neuron in periphery prevents GTO inhibition

- may be related to 20-30%MVC; limited due to pain of contraction

23

Physiological muscle fiber stimulation

- muscle made up of many MU
- during sustained physiological contraction, different MU will fire asynchronously with different MU turning on/off at different times, resulting in a smooth muscle contraction and also delays the onset of fatigue

24

Parameters: Strengthen weak muscles

Goal?

- Produce strong muscle contraction
- augment voluntary contraction by the patient

25

Parameters: Strengthen weak muscles

Parameters:
- Pulse duration
- Pulse rate
- On time
- Off time
-Ramp time
- Current intensity
- Time/reps

- PD >250usec
-PR 50-80Hz
-On 10s
-Off 3-4x the on time
-Ramp 2-5sec
-Current intensity high (produce ms contraction)
- Time/reps: vary. Lower number of reps is generally suggested since the goal is to increase strength

26

Parameters: Retrain inhibited muscle

Goal?

Low grade contraction to facilitate the feel of a voluntary contraction. Pt instructed to contract the muscle along with the electrical stimulation as part of the retaining process

27

Parameters: Retained inhibited

Parameters:
- Pulse duration
- Pulse rate
- On time
- Off time
-Ramp time
- Current intensity
- Rime/reps

PD > 250usec
PR 50 Hz
On 2-3sec
Off 3-4x the on time
Ramp Long (2-5)
Current Intensity just enough to produce contraction
Time/reps: depends on therapeutic goals (e.g. 30 reps or to fatigue)

28

Parameters: Edema control via muscle pump

Goal?

Low grade contraction to facilitate muscle pump but I minimize fatigue

29

Parameters: Edema Control via muscle pump

Parameters:
- Pulse duration
- Pulse rate
- On time
- Off time
-Ramp time
- Current intensity
- Rime/reps

- PD > 250usec
- PR 30-50Hz
- On 5-10s
- Off 1:1 ratio ON time
- Ramp time short 2-3 secs
- Current intensity: just enough to produce a contraction
- time/reps: 30 mins, several time per week

30

NMES: ACL repair

Goal & Effect

Goal:
- combat disuse atrophy of the quadriceps, often focusing on VMO activation

Effect:
- NMES combined with exercise may be more effective in improving quadriceps strength than exercise alone

31

NMES: TKA

- Used as an adjunct treatment to standard rehab and had significantly great improvements in strength, functional performance, and knee extension ROM (at 3.5 weeks and 1 year follow up)

32

NMES: quad strengthening (unimpaired)

- no better than exercise, but volitional exercise is better than NMES

33

NMES: quadriceps strengthening (impaired quads)

Post-surgery/injury: NMES not better than volitional exercise
In-cast or immobilization patients: NMES better than no exercise and volitional in-cast exercise

34

NMES: quadriceps strengthening for adults with advanced disease (COPD, chronic respiratory failure, thoracic cancer, chronic heart failure)

- Significant improvement in quad strength and 6MWT
- Some weaker evidence of increased muscle mass

35

NMES for Knee OA in Elderly

- Moderate evidence than NMES alone or NMES combined with exercise improves isometric quad strength

36

Functional Electrical Stimulation (FES): example

- uses electrical stimulation to aid in functional movements
Example: TA stimulation during gait to assist with foot clearance; stimulation is triggered when heel leaves the ground

37

EMG Biofeedback: what is it and why is it used?

Tool for muscle retraining
- surface electrodes are placed over the target muscle
- voluntary activation of the target muscle results in MU action potential that can be sensed by electrode
- patient received immediate visual or audio feedback when the target muscles contract

38

EMG biofeedback: clinical use

INHIBITED MUSCLES
- e.g. VMO following a knee injury - patient gets immediate feedback when he/she is able to activate the target muscle

OVERACTIVE MUSCLES
- e.g. upper traps - patient gets immediate feedback that the muscle is over active during exercise and then they can adjust mechanics to “turn the muscle off”

39

Can NMES be used for lower traps or is it contraindicated?

- Concern: NMES may stimulate the intercostal muscles and effect breathing (do not perform on national exam - there are alternatives to NMES)

- Target: retrain lower trap activation, then use low intensity that is unlikely to case deeper muscles to fire.

- Precaution: pt with little muscle mass or hx of breathing problems

40

Trouble with intensity (sensory - pain)

Consider using a lower pulse duration
- Strength-Duration curve: shift to the left gives you more leeway between sensory, motor, and pain stimulation
- Intensity: only change during on-time so patient can give you immediate feedback
- Other: active muscle contraction when electrical stimulation is applied