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shoulder musculature

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  • shoulder musculature

    I am a graduate student from Australia who, as a first experiment, needs
    to document the biomechanics of certain shoulder muscles in order to
    later use this information to help interpret EMG data from shoulder joint
    movements (isometric and isotonic flexion/extension and
    abduction/adduction) in subsequent experiments to follow.

    The 3 muscles I am interested in are the pectoralis major, latissimus
    dorsi and the deltoid. The data I would like from predetermined
    (cadaveric) segments of these muscles are; the lines of action of each
    intramuscular segment and the angle of the line of action from the
    intended plane of movement, the moment arms and the axis of rotation
    (ICR) of the glenohumeral joint for the ranges of movement utilised
    (isotonic). Optimally, during the EMG experiments where miniature
    surface electrodes are placed on the subject's segments I would like to
    know the above information for each segment at any stage in the movement.
    Also useful would be an indication of the force each segment was

    Some of the questions I have been pondering over are;

    1. Is there one easy way that all this information can be gathered
    preferably in vivo. Have looked at MRI (Rugg et al, 1990) but am not sure
    whether the shoulder is an applicable joint and whether the images for
    the segments would be clear enough. Have also looked at articles by Van
    Der Helm and colleagues 1991, 1992 and 1994 but have been advised that
    spatially digitizing 3D in vivo is difficult.

    2. Would cameras and markers on segment origin and insertion followed by
    digitizing give adequate 3D representation along with the Reuleaux method
    (1875) for the axis of rotation work?

    3. Is the straight line approach in comparison to the centroid line
    approach (Jenson and Davy, 1975) adequate for these muscles and hence the
    moment arm determination for each segment of each muscle?

    Comments on any of the issues mentioned would be greatly appreciated and
    a list of responses will be posted in the usual manner.

    James Wickham
    Department of Biomedical Science
    University of Wollongong
    Northfields Avenue, Wollongong 2522
    NSW, Australia

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