MatLab Code for Post-Processing EMG Data

[Dan Robbins]

Re: MatLab Code for Post-Processing EMG Data

Thanks for the replies, I have a had a look on Amazon and both these books luckily have a 'look inside' option, the Roberto Merletti and Philip Parker book looks like it could do the job, it’s a bit expensive at £90 but I might be able to get a loan through our library so I can judge before parting with money.

I have been speaking to the guys in our engineering department and the general feeling is that considering EMG is post processed we should not be using analogue filters at all and digital filter are definitely the way forward. Has anyone got any experience or thoughts on this point of view?

[Ross Miller]

Re: MatLab Code for Post-Processing EMG Data

I will third the Gans & Loeb textbook recommendation, it's an excellent reference to have.

[Mandy Salinas]

Re: MatLab Code for Post-Processing EMG Data

Hi-
I have read through the postings. I'm post-processing my EMG data. What I mean by that is that I'm not applying any filters real-time during the data collection.

My processing steps are:
1. De-mean the raw signal (subtract out the mean)
2. Apply a FIR Bandpass Filter (20-300 Hz)
3. Apply a Notch Filter at 60 Hz
4. Rectify (take absolute value)
5. Apply an FIR LowPass filter with cut-off freq = 10 Hz (To get Linear Envelope)

My questions:
Many of the postings suggest the MATLAB function 'butter' - IIR (recursive) filter. B/c you can do it real-time? Or is it b/c FIR filters takes too much computer time?

Does anyone apply the Notch Filter at 60 Hz? Any thoughts on this? I see a large spike at 60 Hz when I run an FFT on my signal. I think I'm picking up noise from the motorized treadmill.

Any thoughts on cutoff frequencies used to get the linear envelope? I used 10 Hz due to papers I've read. I'm curious what others are using. I'm collecting leg EMG & later I might collect arm EMG as well.

I would appreciate any comments. Thank you.

Mandy

[Mandy Salinas]

Re: MatLab Code for Post-Processing EMG Data

Sorry - to be clear. I'm doing all the processing in MATLAB.

Mandy

Hi-
I have read through the postings. I'm post-processing my EMG data. What I mean by that is that I'm not applying any filters real-time during the data collection.

My processing steps are:
1. De-mean the raw signal (subtract out the mean)
2. Apply a FIR Bandpass Filter (20-300 Hz)
3. Apply a Notch Filter at 60 Hz
4. Rectify (take absolute value)
5. Apply an FIR LowPass filter with cut-off freq = 10 Hz (To get Linear Envelope)

My questions:
Many of the postings suggest the MATLAB function 'butter' - IIR (recursive) filter. B/c you can do it real-time? Or is it b/c FIR filters takes too much computer time?

Does anyone apply the Notch Filter at 60 Hz? Any thoughts on this? I see a large spike at 60 Hz when I run an FFT on my signal. I think I'm picking up noise from the motorized treadmill.

Any thoughts on cutoff frequencies used to get the linear envelope? I used 10 Hz due to papers I've read. I'm curious what others are using. I'm collecting leg EMG & later I might collect arm EMG as well.

I would appreciate any comments. Thank you.

Mandy

[Stuart Miller]

Re: MatLab Code for Post-Processing EMG Data

Hi Stuart,

I'm sorry, the high pass filter must be placed befor the full wave rectification filter. The cut-off frequency is about 30Hz.

What is the aim of your project?

You can contact me via "hassani.walid (at) gmail.com"

Regards,

Walid

Hi Walid,

Thank you for the information. I've been working with EMG on a number of projects and have always been questioning the processing methodology undertaken. As I'm sure you know, there is so much variability in how the processing is performed, with various reasons why. This is probably partly due to the natural variability of the signal, the differences in hardware, the differences in the validity of the data (referring to preparation etc), what you are using EMG for, amongst numerous other things. Even on this small listing there are a fair few different procedures suggested.

Stuart