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Normalizing EMG data

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  • Normalizing EMG data

    Dear Biomch-L colleagues,

    A graduate student of mine is working on a thesis and has the need
    to collect and analyze EMG information for "normal" individuals and
    post-op "ACL" patients. In order to compare muscle activity among
    subjects and between groups, the EMG data must be normalized in
    order to account for "...individual differences in subcutaneous fat, muscle
    geometry, and other variances..." (Soderberg & Cook, 1984). Traditionally,
    the criterion used to normalize EMG has been a maximum voluntary
    contraction, MVC, of the involved muscles, as suggested by a variety
    of sources including Basmajian & DeLuca (1985) and Soderberg &
    Cook (1984). While the use of MVCs to normalize EMG data have been
    recommended, the MVC value is often difficult to obtain and/or difficult
    or inappropriate to relate to the functional activity of interest. In the case
    of the current study, we are concerned that post-op ACL patients may not be
    able to tolerate the forces involved in a MVC. The question is: are there
    criterion values other than MVCs (e.g., a submax contraction at a standardized
    workload or effort, etc.) that may be appropriate and that will allow valid and
    meaningful comparisons among subjects? A search of the Biomch-L
    archives and a perusal of approximately 500 titles available on Medline and
    WorldCat have been little help relative to this specific question. Additionally,
    the International Society of Electrophysiological Kinesiology (ISEK) EMG
    Standards (reprinted in Dainty & Norman, 1987) did not really address the
    normalization problem. I welcome the opinions, experiences, and
    recommendations of this group and will be happy to post a summary of replies.


    Basmajian, J. V. & DeLuca, C. J. (1985). Muscles Alive. Baltimore: Williams
    & Wilkins.

    Dainty, D. A. & Norman, R. W. (Eds.) (1987). Standardizing Biomechanical
    Testing in Sport. Champaign, Illinois: Human Kinetics.

    Soderberg, G. L. & Cook, T. M. (1984). Electromyography in Biomechanics.
    Physical Therapy, 64(12), 1813-1820.

    Thank you in advance!


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    :: C. Roger James, Ph.D.
    :: Assistant Professor, Biomechanics
    :: Department of Health, Physical Education & Recreation
    :: and
    :: Center for Sports Health & Human Performance
    :: Box 43011 Texas Tech University
    :: Lubbock, Texas USA 79404-3011
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