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EMG digital filter and processing

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  • EMG digital filter and processing

    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