E-stim for muscle contraction

Question 1

neuromuscular electrical stimulation

Answer 1

• the use of electrical current to produce muscle contraction in innervated muscle
• requires intact PNS

Question 2

Use of NMES

Answer 2

• populations with CVA, spinal cord injury, sports related injury, post operative conditions and healthy athletes
• can strengthen muscle reeducate, retard/prevent muscle atrophy, reduce spasticity, and help in managing edema via the muscle pump action

Question 3

Physiologically induced muscule contraction

Answer 3

• activate Type 1 slow twitch first
• low contraction force
• slow speed of contraction
• asynchronous recruitment of motor units
• fatigue resistant
• atrophy resistant
• smooth onset

Question 4

E-stim induced muscle contraction

Answer 4

• fast twitch type 2 activated first
• high contraction force
• fast speed of contraction
• synchronous recruitment (all or non)
• fatigues quickly
• atrophies quickly
• have rapid jerky onset
• patients should also preform active contractions to stimulate type 1

Question 5

Mechanisms of strengthening: overload principle

Answer 5

• increased load and higher force contraction leads to increased strength
• with e-stim force is increased by manipulating: intensity, pulse duration (width), electrode size, external resistance/positioning (AG, GM etc.)

Question 6

Mechanism of strengthening: specificity principle

Answer 6

• muscle contraction specifically strengthens the fibers that contract
• therefore e-stim has a greater effect on type 2 fast twitch fibers

Question 7

Parameters for muscule strengthening

Frequency/intensity/duration

Answer 7

• high duration between 200-300 microseconds
• shorter duration (150-200) for smaller muscles
• longer duration (250-350) for larger muscles
• shorter durations require higher intensity
• frequency usually 35-70

Question 8

how to get a tetanic contraction

Answer 8

• lower frequency creates separate muscule twitches
• as twitches get closer together (increased frequency) it creates a tetanic contraction

Question 9

types of contractions with ES

Answer 9

• twitch
• un-fused tetany
• tetany

Question 10

twitch contraction

Answer 10

• the smallest contraction that can be elicited from a muscle 1-5pps

Question 11

un-fused tetany

Answer 11

• some twitch and some tetany
• 5-20 pps

Question 12

tetany

Answer 12

• smooth, strong contraction produced in response to faster delivery of action potentials
• 30-50 pps
• up to 70pps you increase the effective energy of the contraction
• above 100 pps the muscle will fatigue faster

Question 13

waveform used to stimulate innervated muscle

Answer 13

• pulsed biphasic waveform - wide width and rate of 35-70
• russian protocal or russian stim

Question 14

Russian stim

Answer 14

• present in the machine
• consists of medium frequency AC with a carrier frequency of 2500 Hz delivered in 50 bursts per second
• 10 millisecond burst duration and inter-burst interval

Question 15

Electrode placement for muscle contraction

Answer 15

• usually 2 electrodes per muscle
• 1 electrode on the motor point
• usually muscle belly the other aligned parallel to the muscle fibers at least 2 inches a part

Question 16

Patient positioning for muscle contraction

Answer 16

• related to the goal of isometric muscle contraction or isotonic motion

Question 17

on/off time

Answer 17

• allows for rest between contractions
• usually start with 1:5 ratio for strengthening
• depends on your goal (muscle pumping or strengthening)
• can adjust on/off time to make it harder or easier

Question 18

what is the best on/off time for
1. muscle strengthening/re-ed
2. edema reduction using muscle pump
3. muscle spasm reduction (produce fatigue)
4. functional E-stim

Answer 18

1. 10 seconds on/50 seconds off
2. 2-5 seconds on/2-5 seconds off
3. 2-5 seconds on/2-5 seconds off
4. as needed for functional activity

Question 19

ramp time

Answer 19

• allows for a gradual increase and decrease of force
• generally 1-4 seconds

Question 20

current amplitude

fore-stim muscule contraction

Answer 20

• desired strength of contraction
• strengthening if uninjured = 50% maximum voluntary isometric contraction (MVIC)
• recovery from injury or surgery >10% of MVIC
• Ms spasm reduction/edem = visible contraction

Question 21

Functional electrical stimulation

Answer 21

• can be used to help with walking or other activities and can be worn

Question 22

Denervated muscle for muscle contraction

Answer 22

• direct current
• when muscle becomes denervated by injury or disease it can no longer contract physiologically or with NMES
• it requires stimulation of the muscle fiber directly

Question 23

requirements for denervated muscle

Answer 23

• longer duration (width) stimulus so interrupted direct current applied for number of seconds to create contraction
• duration controlled by therapist
• requires higher intensity so it is uncomfortable

Question 24

when to use stim for denervated muscle

Answer 24

• if the nerve is not intact or functioning it requires stimulation of the muscle fiber directly

Question 25

How to set up denervated e-stim

Answer 25

• DC current
• long duration
• high intensity
• monopolar set up (net charge)
• watch for changes in the skin