EMG during Walking : On/Off detection

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Marie-Caroline
Marie-Caroline 2024-2-9
回答： Alex Wu 2024-3-25
I would like to define an accurate threshold to detect ON/OFF bursts.
Please find attached my EMG signal (rectified).
I am able to code when the muscle activity exceeds the double or triple SD rang (i.e. the muscle is defined to be
“On” or activated).
Threshold=std(A(1:800,1)).*(2.5)
if A>Threshold
DataON=A>Threshold
DataONOFF=diff(DataON)
BUT : Because single spontaneous spikes can easily exceed the SD range, I need to define
a minimum time (minimum subperiod duration) that the EMG signal has to constantly stay OVER the threshold
to be accepted as “On” (e.g. 50 ms). So I would like to translate something like that :
if A>Threshold (and data over threshold during 50 ms)
  2 个评论
Star Strider
Star Strider 2024-2-9
The 'Threshold' value is really low — about 17.5 — with the peaks in the range of 100 to 2000. Also, the sampling frequency is missing, so it’s not possible to determine the activation duration. I would use a differerent approach to this, however I first need to understand what exactly you want to do.
It would also help to know what release you’re using, and if you have the Signal Processing Toolbox.
Marie-Caroline
Marie-Caroline 2024-2-9
The sampling frequency is 2000 Hz.
My objective is to define subperiods (each walking step) within my entire trial.
I use Matlab R2023b and have the Signal processing Toolbox.
Many thanks in advance for your help !

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采纳的回答

Alex Wu
Alex Wu 2024-3-25
Hi Marie-Caroline
You may find sigrangebinmask useful.
Please check this example Label High-Amplitude Regions in EMG Signal, where we use sigrangebinmask function to label regions where the EMG amplitude is greater than 0.25 (threshold) for at least 0.5 seconds (minimum subperiod duration).

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