Functional electrical stimulation (FES)

Question 1

What is FES used for?

Answer 1

Activating muscles

Question 2

How does FES activate the muscle?

Answer 2

Electrodes are placed on the skin above the muscles. Then trains of electrical signals are sent through the muscle. The muscle motor nerves are activated, in turn activating the muscle

Question 3

What gets activated first, nerves or muscles? Why?

Answer 3

Nerves, because they have a lower threshold

Question 4

Which of the following is depolarised? Cathode or Anode?

Answer 4

Cathode

Question 5

What is the effect of having unequal size of anode/cathode?

Answer 5

Makes current more or less dense, increasing precision.

Question 6

Name one side effect of too high current

Answer 6

Skin burns

Question 7

Explain the effect of higher amplitude or width of the pulses

Answer 7

Both lead to a stronger nånting

Question 8

Explain “balanced asymmetric bipolar”

Answer 8

The compensating pulse is smaller (in amplitude) but longer in time to not activate the nerves under the anode side, eller nåt

Question 9

True or false?
Larger pulse = larger contraction of muscle

Answer 9

False

Question 10

Why are different motor units activated after each other?

Answer 10

So that the total tension in the muscle is “quite smooth”

Question 11

How does FES activate the muscle in comparison to how the brain does?

Answer 11

Brain: Smaller motor units first
Electrical stimulation: Large motor units first, the same motor unit with every part, need higher frequencies

Question 12

What is the biggest drawback of FES?

Answer 12

Fatigue. The muscle can no longer produce movement after ish 20 sec

Question 13

What kind of control system is usually used for FES, and why?

Answer 13

Open loop, due to the complexity of the human body

Question 14

How can FES be used for spinal cord injury specifically?

Answer 14

The potentials produced by the brain can be used in the affected body part, but signals must go around non-functioning body parts.

Question 15

What are matrix electrodes used for?

Answer 15

Increase selectivity. For example, allowing to extend only one specific finger, for example, pointing with the index finger

Question 16

What are the challenges with controlling muscle? Explain the specific issues for the following methods:
1. PID controller
2. Inverse plant model

Answer 16

Non-linearity and time invariant due to muscle fatigue
1. Poor results since the method is developed for linear systems
2. Some aspects cannot be reversed due to non-linearity

Question 17

What frequencies does the brain vs FES use for activation?

Answer 17

Brain: 6-8Hz
FES: 20-40Hz

Question 18

What is used to solve the issue with controlling muscle fatigue?

Answer 18

An adaption mechanism in the closed loop to direct model and inverse model

Question 19

What is the primary target for nerve-muscle stimulation using FES?

Answer 19

Muscle nerves

Question 20

What is the primary target for reflex simulation using FES?

Answer 20

Cutaneous sensory nerves

Question 21

What is FET?

Answer 21

Therapy in which Paretic patients are asked to exercise functional tasks assisted
with a neural prosthesis that controls the opening, grasping, holding, and releasing
functions.

Question 22

What does FET control (upper limb)?

Answer 22

The flexor and extensor
muscles

Question 23

How often is FET done?

Answer 23

Daily, 30-minutes long sessions, during
three consecutive weeks.

Question 24

What does FET control (lower limb)?

Answer 24

Targets Nociceptive Withdrawal Reflex to control Hip flexion, Dorsi-flexion, Inversion, Plantar flexion (tror jag man kan formulera det)