Lecture 9 - Electromyography

Question 1

Surface Electromyography

Answer 1

To measure:

Place on belly of muscle, aligned with the direction of muscle fibers (pennation angle)

1. Shave
2. Sand paper
3. Clean with all swab (to get rid of oils)

Minimize the amount of error/resistance in the measuring

Recification when measuring: means to make all negative values positive to avoid calculating to 0

Smoothing: can be done by filtering and averaging the rectified EMG

The rectified and smoothed EMG trace closely corresponds to muscle force output

More EMG=higher force

Question 2

Maximal voluntary contraction

Answer 2

Often times we normalize the EMG to each participants highest amplitude obtained during a MVC

Question 3

Indwelling Electromyography

Answer 3

aka fine wire

The two electrode leads (wires) pass through the cannula of a needle. The needle gets inserted into the target muscle and withdrawn, however, the wire remains in, hooked on the muscle fibres. (alpha motor neurons in ventral horn). Measuring motor units

Used cause you can get deep under skin and small amount of motor units

You can extract single MU spikes but not using surface EMG

Question 4

Recruitment and Data

Answer 4

Extract the individual motor unit AP from the raw signals

Recruitment order= smallest to largest
decruitment order= largest to smallest

Smaller motor neurons turn on at a lower force output

testing: asking if smaller vs larger
MVC % instead of force output

Question 5

Training effects on motor neurons

Answer 5

With strength training we can increase the amplitude of EMG during a maximum voluntary contraction

Increase in force and EMG amplitude with training (faster, stronger, better)

more force=more EMG

Can increase in size in muscle and motor neuron

Motor unit spiking patterns change on what type of motor units