EMG

Question 1

what does surface EMG measure

Answer 1

electrical differences under the surface of the skin using electrode patches

Question 2

what is the pennation angle and why is it important in surface EMG

Answer 2

direction of muscle fibres

• need to align electrode pads with it in order to measure the same AP propagation

Question 3

what is rectification of EMG

Answer 3

“absolute value” of EMG

makes all negative values positive (can now take an average of the data without it being close to 0 and retaining its peaks )

Question 4

what is smoothing an EMG

Answer 4

flitering and averaging the rectified EMG

Question 5

what does a rectified and smoothed EMG closely correspond to

Answer 5

force output (linear relationship with EMG)

Question 6

what can you do in indwelling EMG that you can’t do in surface EMG

Answer 6

decompose the raw EMG signal into individal MU APs because the wire is hooked in the muscle fibre

• can extract single MU spikes

Question 7

what is the main use of indwelling EMG

Answer 7

to look at size recruitment of MUs

Question 8

does the distance of the MU to the wire in indwelling EMG make a difference

Answer 8

yes - farther away = smaller traces of APs

Question 9

what is high density EMG

Answer 9

same concept as surface EMG just with lots of surface electrodes in a small area

Question 10

how does high density EMG differ from surface EMG

Answer 10

measure the same things but high density has more data that is able to be decomposed into single MUs