Electromyography

Question 1

What is the aim of Electromyography?

Answer 1

The aim of Electromyography is to quantify muscle movement/accuracy. How they work together or against each other.

Question 2

What do some areas of Electromyography look into ?

Answer 2

Some areas of electromyography focus on the understanding and treatment of motoneuron disease.

Question 3

How do they quantify motoneuron disease?

Answer 3

To quantify motoneurons disease they use electromyography, and stick a needle in the muscle and try to measure the number of active motoneurons cells they have in the muscle. They may also look at conduction, velocity and of the muscle, and look at the myelin sheath.

Question 4

Electromyography can be used to quantify motoneurons disease, what else can it do?

Answer 4

They also look at the conduction and velocity of the muscle in this way.

Question 5

What type of people benefit from using electromyography?

Answer 5

People training in sports, as they want to see how muscle activity and the electrical activity correlate with things such as oxygen intake and performance.

Question 6

What else has benefited from electromyography?

Answer 6

Prosthetic control has also benefited from electromyography, along with rehabilitation treatment.

Question 7

What is kinesiology?

Answer 7

Kinesiology is the scientific study of human or non-human body movement.

Question 8

What is EMG?

Answer 8

Electric Muscle Graphs. Electromyography is the study of muscle function through the inquiry of the electrical signal the muscle emanate.

Question 9

Where can the EMG sit on the body?

Answer 9

• The EMG can sit on the surface of the skin
• The EMG can sit under the surface of the skin, but outside the muscle
• The EMG can sit in the muscle

Question 10

Putting the EMG under the surface of the skin, outside the muscle is called what? Is it possible?

Answer 10

Putting an EMG under the surface of the skin isn’t yet possible, this is called epimysium electrode.

Question 11

What is an epimysium electrode?

Answer 11

This is an EMG that is put under the surface of the skin, but not inside the muscle.

Question 12

Putting the EMG inside the muscle is called what? Is it possible?

Answer 12

Putting an EMG inside the muscle isn’t yet possible, however this is called inter-muscular recording.

Question 13

What is inter-muscular recording?

Answer 13

This is the idea that they can put EMGs inside the muscle.

Question 14

What are the two options available currently for fitting an EMG?

Answer 14

The only two options are fitting an EMG in the skin, or putting aluminium needles inside the muscle to record.

Question 15

What is important to know when reading EMG signals?

Answer 15

It is important to know if it is noise or if it is the real signal. Getting the right signal takes some practice.

Question 16

What does the rest period of a EMG signal look like?

Answer 16

The rest signal of an EMG signal shouldn’t look like a flat line, it has some action potentials (tiny pulses coming from the brain), this is spontaneous activity. They are the single unit, motor commands that the brain sends .

Question 17

What happens to the motor commands when a movement happens?

Answer 17

When a movement happens, many motor commands are fired and superimposed on top of one another, causing the muscle to move.

Question 18

How can we tell the difference between noise and real signals?

Answer 18

Looking at the duration of the signals can elude to if its real or just noise, as noise is usually very fast (1 millisecond)

Question 19

Explain what happens when a control signal comes from the brain.

Answer 19

The brain intends to make a movement, so a signal is generated, travelling down the spinal chord and then comes to the level of the spinal chord that is in charge of controlling that body mass. Signal goes to the ventral area, triggering motoneurons, each motoneuron is connected to a different muscle fibre.

Question 20

True or false: All units of the spinal chord serve down stream?

Answer 20

True, this is why if someone has an injury to the spinal chord, anything below where the injury took place will be affected and loose the signal, loosing control of the muscle, unless it can be recovered with intervention.

Question 21

After a signal has been triggered by the brain, and has moved to the ventral area, what happens next?

Answer 21

So each motoneuron is connected to a different muscle fibre. For the same low level signal, the fast recruited signals are recruited first. As time passes and as more energy is put into that drive, then the slow recruited fibres are recruited too. So there is a time difference between when the muscle fibres are recruited .

Question 22

What sizes are the action potentials generated for the faster and slower recruited signals?

Answer 22

MU Electric Signal, MU Force Output:
The action potentials generated for the first faster recruited signal are very small. For the secondary motor unit they are slightly larger, and the slow recruited fibres have significantly larger action potentials, but are delayed.

Question 23

Is the shape of the action potentials dependent or independent to the shape of the input?

Answer 23

The shape of the action potentials is totally independent to the shape of the input (motoneuron firings). The shape of the input is fixed (binary) and information is coded in the rate of that, rather than the shape.

Question 24

We know that the shape of the action potentials is totally independent to the shape of the input. But how is information coded in the motoneuron firings?

Answer 24

The shape of the input is fixed (binary) and information is coded in the rate of that, rather than the shape.

Question 25

How is the signal process highly functioning?

Answer 25

This is because the same signal, depending on which muscle fibre will generate different signals in the action potentials, meaning it is highly functioning.

Question 26

If you want to react to something very quickly, what is the muscle signal used?

Answer 26

If wanting to react to something very quickly, the fast recruited signals are recruited, and very fine movements can be done

Question 27

As the body grows, it learns how to recruit signals effectively. If a lot of force is required, what is the muscle signals used?

Answer 27

If a lot of force is required, the more slower recruited signals are used, they can generate more force output.

Question 28

The overall signal recorded on the surface of the skin is a combination of what?

Answer 28

The overall signal recorded on the surface of the skin is the combination of the superposition of the action potentials.

Question 29

What is the force output a combination of?

Answer 29

The force output is a combination of the individual forces that the units produce.

Question 30

A sprinter would be more interested in which types of signals in order to better performance?

Answer 30

A sprinter would be more interested in the faster recruited signals in order to better performance.

Question 31

A long distance runner would be more interested in which type of signal to better performance?

Answer 31

A long distance runner would be more interested in the slower recruited signals in order to better performance.

Question 32

What can cause the signal to have error in the reading of an EMG?

Answer 32

Fat under the skin can cause interference and can cause a reading to have an error.

Question 33

What may distort the reading if you are trying to record activity from a single muscle fibre?

Answer 33

The other fibres may distort the reading if you are trying to record activity from a single muscle fibre.

Question 34

How can you take a reading of a single muscle fibre?

Answer 34

A very fine needle would need to be used on the muscle.

Question 35

How difficult is it to get an EMG?

Answer 35

To its detriment, electromyography is too easy to use, and consequently too easy to abuse.

Question 36

What are the 9 intrinsic factors that affect an EMG?

Answer 36

1. Blood flow
2. Subcutaneous tissue
3. Lactic acid
4. Fibre type
5. Fibre diameter
6. Number of active motor units
7. Motor unit firing rate
8. Motor points
9. Conduction velocity

Question 37

What are the 8 extrinsic factors that affect an EMG?

Answer 37

1. Skin impendence
2. Sensor location (muscle can move under skin)
3. Signal resolution
4. 50/60Hz noise
5. Muscle cross talk
6. Sensor bandwidth
7. Movement artefact
8. Sampling rates

Question 38

What do we know about the sensor used in EMG?

Answer 38

• It meets several FDA regulations

- Made by mechanical and electrical engineers

Question 39

What are some applications for EMG?

Answer 39

• Sports performance
• Exercise physiology
• Motor control
• Rehabilitation
• Animal research
• Neuromuscular diseases

Question 40

What is the sEMG signal characteristic and compuation of muscle effort (force)?

Answer 40

Amplitude, and the computation is RMS

Question 41

What is the sEMG signal characteristic and computation of muscle activation timing?

Answer 41

Amplitude threshold, the computation is RMS and then threshold.

Question 42

What is the sEMG signal characteristic and computation of localised fatigue?

Answer 42

Decrease in median frequency, the computation is a median frequency trend curve.

Question 43

What is the sEMG signal characteristic and computation of biofeedback?

Answer 43

Changes/interaction and the computation is quantitative

Question 44

There exists a relationship between the surface EMG and what?

Answer 44

There exists a relationship between the surface EMG and the amount of force.

Question 45

How can the amount of force a muscle can generate be estimated?

Answer 45

The amount of force a muscle can generate can be estimated by the magnitude of the muscle activity. Root mean squared. Increase in force applied= Increase in EMG signal, but a non-linear relationship.

Question 46

What is important to look at if your interested in seeing if the muscles contract at the right time, or if they co-contract or not?

Answer 46

Muscle activation timing. If you are interested in seeing if the muscles contract at the right time, or if they can co-contract or not, looking at on-off times are very important.

Question 47

What do muscle fatigue signals show?

Answer 47

Shows the variation of signals over a set time, fast recruited signals going first, shows how the muscles act after exercise. Also may show how it changes after intervention.

Question 48

What is biofeedback?

Answer 48

This is like the bars which you try to control the height of each bar independently or together, with each bar being associated with a different muscle. This may be done after injury to asses if the muscle is being used. It involves patient interaction and participation with real time feedback.

Question 49

After limb loss, if the muscles are still there, sensors can be placed on the stump to measure the electrical activity of the muscle. What machine is used to analyse?

Answer 49

This then goes into a movement classification, this is a machine that looks at the signatures of different movements and tries to work this out from the signal, and work out the intention of the movement. This means they could potentially drive a prosthesis.