Myo-Electrical Stimulation of Muscle

Question 1

What is the purpose of Myo-electric stimulation

Answer 1

Achieve muscle contraction and explore its applications

Question 2

Def: Electricity

Answer 2

The force created by an imbalance in the number of electrons at two points

Question 3

Electrons

Answer 3

Negatively charged particles

Question 4

Current

Answer 4

The movement of electrons from higher potential to lower potential

Question 5

Ampere

Answer 5

The unit of current or rate of electron movement

Question 6

Voltage

Answer 6

Electromotive force created by the difference in electron population between two points

Question 7

Resistance

Answer 7

Opposition to electron flow measured in ohms

Question 8

Watts

Answer 8

Units of electrical power = to volts x amps

Question 9

Capacitance

Answer 9

The ability of a material to store electricity

Question 10

Ohm’s Law

Answer 10

Current through a conductor is directly proportional to the potential difference(voltage) and inversely proportional to resistance

Question 11

1- 10mA shock

Answer 11

Person will feel little or no electrical shock effects or even the sensation of shock

Question 12

10-20 mA shock

Answer 12

Painful shock will occur like a jolt but muscle control will not be lost

Question 13

20-75 mA shock

Answer 13

Shock is more serious. Pain jolt and muscle control will be lost resulting in the inability to let go of the current source

Question 14

75-100mA shock

Answer 14

Ventricular fibrillation of the heart occurs and damage can result

Question 15

100-200 mA shock

Answer 15

Heart can stop and death can occur if medical attention is not administered quickly

Question 16

over 200 mA shock

Answer 16

Severe burns, internal organ damage and the heart can stop due to the pressure that the chest muscles place on the heart
- heart does not experience fibrillation and the person can survive if the source is removed quickly

Question 17

Methods of stimulation

Answer 17

1. Percutaneous electrodes - placed on the skin over the target muscle
2. implanted electrodes - surgically placed within paralyzed muscle for chronic use

Question 18

Electrode set up

Answer 18

• Bipolar arrangement
• Activates muscle tissue between electrodes

Question 19

Simulator control

Answer 19

• very short square-wave pulse
• short duration pulses enhance safety, reducing the risk of tissue damage
• Voltage adjusted to increase the number of recruited muscle fibers
• Frequency adjusted to increase the firing rate

Question 20

Effect of voltage on single pulse stim

Answer 20

• low voltage: a small voltage excites only a few muscle fibers, resulting in a small twitch force
• Increased voltage: as voltage increases, more muscle fibers are recruited, leading to a larger twitch force
• Maximal Recruitment: At a certain voltage, all recruitable fibers are active and further increase in voltage do not increase twitch force

Question 21

Muscle force and stimulus frequency

Answer 21

• Higher stimulus frequency = greater twitch summation
• Modulated by the CNS

Question 22

Recruitment in voluntary contractions compared to myo-electrical stimulation

Answer 22

VC
- follows Henneman size principle (small to large as force increases)
ME
- recruitment based on proximity to electrode and impedance

Question 23

Simultaneous Firing in voluntary contractions compared to myo-electrical stimulation

Answer 23

VC
- Fibers in a motor unit fire together, but different motor units have different firing rates
- Results in a smooth, graded contraction and fine motor control
ME
- Simultaneously activates all recruited fibers, treating the muscle as a single motor unit
- less fine control

Question 24

lack of inhibition in voluntary contractions compared to myo-electrical stimulation

Answer 24

VC
- muscle activation is modulated by mechanisms (stretch reflex, reciprocal inhibition, sensory inputs)
- Safeguard mechanism to prevent injury
ME
- Overrides natural inhibitory mechanisms - increased injury risk
- Requires careful application

Question 25

pain considerations in voluntary contractions compared to myo-electrical stimulation

Answer 25

VC - natural activation is painless if the muscle is uninjured ME - High activation levels can cause pain - Full activation of large muscles may be limited by pain tolerance

Question 26

Functional Electrical Stimulation

Answer 26

Uses myo-electric stimulation to activate muscles

Question 27

FES in spinal cord injuries

Answer 27

- Jerrold petrofsky's innovation applied computer-controlled electrodes to a paralyzed student enabling her to pedal a tricycle - Nan davis is perfect canidate due to minimal muscle atrophy and prior athleticism

Question 28

Benefits of FES

Answer 28

- Enables ambulation on non-wheelchair-friendly terrain - facilitates standing to reach objects - reduced muscle wasting, bone density loss, and bed sores - provides psychological motivation

Question 29

Challenges of FES

Answer 29

FINE MOTOR CONTROL - Current FES lacks the ability to recruit motor units asynchronously or by size principle - Potential improvement with implanted electrodes enabling multi-channel muscle activation WEIGHT BEARING - Paralysis and muscle atrophy (issues holding posture) - Orthotic solutions (hip, knee, ankle orthotics to improve stability and strength) - offer reciprocating gait by coupling hip joints for reciprocal motion FATIGUE - can't simulate fatigue-resistant fibers first SENSORY FEEDBACK - loss of afferent feedback creating difficult with balance and reaction

Question 30

Reciprocating Gait Orthosis with FES

Answer 30

- Combines functional electrical stimulation with a reciprocating gait mechanism - Electrodes placed over key muscles control hip, knee, and ankle flexion/extension via a voice-activated computer - lightweight brace can reduce muscle force required for weight bearing

Question 31

Closed System

Answer 31

Alters future behaviour or state of a system, aims for a desired outcome or state

Question 32

Change-the-state system

Answer 32

Simply changes the state without feedback

Question 33

Control theory

Answer 33

A strategy to select the appropriate inputs

Question 34

Basic parts of control system

Answer 34

- Plant: the system to be controlled - Input: acts on the plant to produce the output - Output: The result of the plant's response to input

Question 35

Closed loop control

Answer 35

- Measures system output with a sensor and compares it to a reference signal - Comparison creates an error signal sent to the controller - The controller's output becomes the input to the plant

Question 36

Central vs peripheral fatigue

Answer 36

Central Fatigue: Decreased neural activation of muscle Peripheral Fatigue: Decreased Neural Activation of the muscle

Question 37

Role of Myo-electrical stimulation on central vs peripheral fatigue

Answer 37

Helps identify the source of fatigue - Subject maintains 50% MVC until fatigue sets in - If myo-electric stimulation maintains force longer, central fatigue is the cause - If stimulation force declines similarly with voluntary effort, peripheral fatigue is the cause

Question 38

Individual muscle isolation

Answer 38

- Research on muscle mechanics often preformed on animals for isolation of tendons and muscles - Voluntary contractions in humans cannot isolate individual muscles, but myo-electric stimulation can - Different strength curves

Question 39

Outcome of strokes

Answer 39

10% recover almost completely 25% recover with minor impairments 40% experience moderate to severe impairments 10% require long-term care 15% do not survive

Question 40

Myo-Electric stimulation in stroke rehab

Answer 40

- Complements traditional rehab by using EMG-triggered electrical stimulation - Enhances neuronal plasticity through proprioceptive and somatosensory feedback - Facilitates reorganization of damaged brain areas and supports physiological learning processes

Question 41

Motor Learning and MES

Answer 41

- MES is effective for children with cerebral palsy and hemiparesis due to birth defects - Provides sensory feedback combined with contraction force - Encourages use of neglected limbs

Question 42

MES and strength gain

Answer 42

LIMITATIONS: - Pain and injury risk restrict maximum stimulation of large muscles - Strength gains primarily observed in severely atrophied muscles RECENT ADVANCES: - Emerging evidence shows benefits comparable to voluntary efforts - Can be used to prevent atrophy but not for weight loss (burns minimal cal)