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Myoskeletal Inverse Dynamics (BIONET Topic 2)

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  • Myoskeletal Inverse Dynamics (BIONET Topic 2)

    Dear Colleagues,

    I would like to immediately respond to the posting of Dr. Tashman
    because I feel that his most impressive and to-the-point description of
    the current situation in clinical gait analysis deserves special

    Here are my (brief) comments:

    1. The "holy grail" of clinical gait analysis (use of
    neuromusculoskeletal system models in conjunction with optimization
    techniques for designing individualized optimal treatment strategies for
    various populations of patients with neuromuscular disorders) does not
    have to remain a distant dream. Already in 1975, I performed the first
    complete, and experimentally verified, optimization of a human motion
    (Hatze, H. (1976) The complete optimization of a human motion. Mathem.
    Biosciences 28, 99-135) after being told by everyone that this would be
    impossible at the present (1975) state of the art. I used a (then)
    rather complex neuromusculoskeletal system model of the leg, devised new
    methods for parameter identification to individualize the model, and
    successfully solved the optimal control problem. The optimal solution of
    the (time-optimal) kicking motion was verified by training the subject
    for optimal performance. Prior to this it was ascertained that the
    subject was unable to find the optimum himself within a reasonable
    period of time. (I did not want to mention this project in my previous
    posting to avoid giving the impression of advertising my work in this
    discussion forum).

    I am convinced that by using more sophisticated models and techniques,
    the "holy grail" of clinical gait analysis can also become reality in a
    concerted effort of several high-level research institutions combined,
    for instance, in a biomechanics network.

    2. I am glad Dr. Tashman underlined the importance of understanding the
    performance criteria underlying the execution of a given task. (Not too
    many researchers recognize this importance). This will be one of the
    discussion topics to come.

    3. His remark that neuromuscular disorders alter essentially all aspects
    of the motor control system is very much to the point and highlights the
    significance of a generally neglected phenomenon.

    4. It is also true, and highly significant, that properties of tissue
    determined in vitro must not (and generally do not) conform to tissue
    properties in vivo. (This is why in my models, the values of the
    relevant parameters are always determined by noninvasive experimental
    in-vivo methods, knowing that these parameter values are VALID FOR A

    5. An excellent remark of Dr. Tashman concerns the whole problem of
    biological adaption of tissue after translocations. This issue is
    frequently ignored despite its importance. It certainly has to be
    considered in advanced modeling.

    I cordially thank Dr. Tashman for his excellent and detailed
    contribution, and for his positive and progressive opinion on the

    Herbert Hatze

    ************************************************** ******
    Prof. Dr. Herbert Hatze
    Head, Department and Laboratory of Biomechanics, ISW,
    University of Vienna

    Auf der Schmelz 6 Tel: + 43 1 4277 48880
    A-1150 WIEN Fax: + 43 1 4277 48889
    AUSTRIA e-mail:
    ************************************************** ******

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