EMG

Question 1

What is measured by surface EMG

Answer 1

asses uscle function by recording muscle activity from the surface above the muscle. However this only provides a limited assesment of muscle activity.

Question 2

HOw does skin affect SEMG

Answer 2

Both fat and skin act as low pass filters for the signal.

Question 3

What are the three main types of EMG recordings

Answer 3

Monpolar - 1 active recording electrode placed over the musclead 1 reference elctrode elsewhere
bipolar - the same but with 2 active electrodes
- Multipolar uses several active electrodes
All sources which are common in both signals are filtered out.

Question 4

Describe the 4 most commonly used types to display SEMG signal

Answer 4

Raw EMG - Processed EMG - Spectral analysis (frequency, ime frequency anaysis) - probability amplitude histogram (time domain)

Question 5

What does SENIAM stand for

Answer 5

Surface Electromyography for noninvasive Assesment of Muslces

Question 6

Whoch properties of electrodes are covered by SENIAM

Answer 6

Shape, Size, Inter-electrode distance, Material, Construction

Question 7

What are the main steps in EMG processing

Answer 7

Rectifying, Smoothing, Filtering (10-500Hz), Notch Filtering (50Hz), Whitening (de-correlating succesive data points)

Question 8

Describe the process of determining the onset and offset of movement

Answer 8

Use High and Low pass filters aswell as notch filter
- Rectify EMG
- EMG smoothing (replacing rectified EMG with an average value over 5 samples).
- Calculate mean and standard deviation of EMG in a relaxed state, prior to muscle contraction
Threshold = mean+2STD of smoothed EMG in relaxed state.
- Define minimum time T1 that EMG should be above the threshold