Muscle Activation

Question 1

What are the types of human muscles?

Answer 1

Skeletal (attached to bones)
Smooth (generates involuntary movement)
Cardiac (found only in heartheart)

Question 2

Explain the structure of a muscle fibre

Answer 2

Muscle fibres are made up of myofibrils bundled together.

Question 3

Explain muscle activation

Answer 3

Muscles move on command from the brain.
Single nerve cells in the spinal cord called motor neurons connect the brain to the muscles.
First, the motor neuron in the spinal cord fires, and then an impulse goes from it to the muscle, travelling down an axon. Then a chemical is released at the end of the axon

Question 4

What are the 3 methods to understand muscle activation?

Answer 4

Physiological Cross-Sectional Area (PCSA)
Electromyography (EMG) (ECG for heart)
Mathematical modelling

Question 5

Explain PCSA

Answer 5

It is measuring the cross-sectional area of the muscle as muscle force is proportional to the area
Muscles aren’t always parallel but sometimes at an angle to pack more fibres. This angle is called the pennation angle.
This process is typically done using medical imaging. Then the area is obtained from the medical image

Question 6

Explain EMG

Answer 6

It is the measuring of the electrical activity produced from muscle activation.
Signal electrodes are placed on the muscles. A ground electrode is also needed and is placed on another part of the body. Signals are then obtained and amplified (signals obtained are small).

For good EMG measurement:
Skin cleaning to remove dead/ dry skin
Electrode needs to be placed in muscle of interest
Cable should be as short as possible to reduce noise
Post processing techniques to improve analysis