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RE: Electromyography in Biomechanics

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  • RE: Electromyography in Biomechanics

    I agree with Jeff Boyd that there is little statistical methodology for
    classification patterns. For the most part, this is the result of
    the noise-like nature of EMG signals, which makes reproducability a

    One way to obtain representative patterns is to calculate an ensemble
    average of cyclic movements, such as walking. A useful literature
    referencemight be:
    Winter D.A. (1984) Pathologic gait diagnosis with computer-averaged
    electromyographic patterns. Arch. Phys. Med. Rehab. 65:393-398.

    This is basically the method that is used in our laboratory for EMG
    research in the horse. There is very little known about the 'normal'
    EMG patterns in horses, and we have only studied normal locomotion
    until now. There are significant differences between individuals
    however, which manifest itself as extra activation periods of certain
    muscles. For instance, we see that some horses actively flex the hoof
    in the swing phase, while others just let inertia do the work. This
    suggests that clinical applications should be possible. We have no
    method (yet) to quantify the differences, we only look at the pattern.
    Winter's paper indicates the problems associated with automated
    parameter extraction from EMG patterns, and also gives some possible

    This is our standard method to obtain the EMG patterns:
    1. Surface electrodes, 20mm separation.
    2. Preamplifier (100x), carried on the subject. Connected by 25m cable
    to recording equipment.
    3. Amplifier (up to 500x), bandpass filter (30-1000 Hz).
    4. Full-wave rectifier, lowpass filter (30 Hz).
    5. Analog to digital converter (12 bit), sampling interval 3 ms.
    6. Ensemble averaging with interactive graphics display for selection
    of strides. Uses signal from hoof-mounted accelerometer for
    automatic stride detection.
    7. Optional smoothing by a digital filter.

    Ton van den Bogert
    Dept. of Veterinary Anatomy
    University of Utrecht, Netherlands.