View Full Version : EMG digital filter and processing

Jon Oliver
11-15-2005, 09:01 PM
Dear all,

I have collected some EMG data of the lower limb muscles during dynamic
exercise, specifically during running and jumping. The raw signal was
collected with a bandpass filter of 8-500 Hz and is now stored on a PC (using
Megawin). Given the dynamic nature of the exercise I need to minimise the
movement artefacts and would like to apply a digital high-pass filter with a
cut-off frequency of 20 Hz. To achieve this I am planning to export the raw
EMG data as an ASCI file and then to apply the digital filter in another

>From reviewing the literature and searching the Biomch-L archives the most
appropriate filter would appear to be a moving average filter, or possibly a
Butterworth filter. My problem is how to apply these filters to the EMG data
that I have. Does anyone out there have any scripts for Labview that would
perform this function, or possibly even any macros for Excel? Once filtered
I would like to determine the amplitude of the EMG signal, so again any
scripts to achieve this would be useful. Finally, I had always assumed that
filtering was the first step in the signal processing, however, I have seen
instances where a filter has been applied after rectification. What is the
purpose of this and is this something I need to consider?

Many thanks,

Jon Oliver
University of Exeter