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Muscular Power During Accelerative Movements

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  • Muscular Power During Accelerative Movements

    Dear Biomch-L users,

    The development of muscular power in humans has generally centred
    around training the stretch shortening cycle capability of the neuromuscular
    unit through activities generally termed "plyometrics". Bosco, Komi, Schmidt-
    bleicher and others have done some excellent work on the contribution of the
    stretch shortening cycle to explosive performance. I would be interested in
    any comments or work done on the accelerative concentric contraction of the
    muscle and how this can be potentiated with training.

    We have developed a device which allows a subject to actually jump off
    the ground with a loaded bar and the eccentric landing can be controlled by a
    braking mechanism. Similarly, in a bench press type movement, a loaded bar can
    be thrown from the chest using an acceleration throughout the movement
    achieving peak velocity at or near the end of the range. Previous attempts to
    train explosively using traditional weights has been hampered by the fact that
    the subject must slow down well before the end of the range where as in most
    athletic situations this is the point of maximum velocity. This may explain
    why this type of training has not been shown to effectively increase muscle
    power output.

    I am proposing to complete a training study involving bench throws.
    One group will train using counter movement throws from the chest. The second
    group will throw the bar but it will be returned slowly to them for the next
    throw thus eliminating the eccentric component preventing them from utilising
    the stretch shortening cycle. Each group will also be divided into subgroups
    based on training load i.e. 10%, 30% and 90% of 1 repetition maximum.

    Pre and post testing will involve measurement of maximum power output
    during both counter movement and static bench throws, basketball and medicine
    ball chest passes into a vertically mounted forceplate to measure impulse of
    impact, emg during both throws and stiffness of the musculo-tendinous system
    in the bench press position.

    It is hoped that such a paradigm will seperate out what proportion of
    enhanced power output is due to increased storage of elastic energy,
    potentiation of the concentric muscle contraction through activation of the
    stretch reflex and the enhanced ability of the muscle to contract
    concentrically during high acceleration.

    It is theorised that some of the increases in power output with
    training are due to an increased ability of the muscle to continue to generate
    force at the high velocities experienced during the later part of the movement
    during say a throw or a jump i.e. a shift in the force velocity curve towards
    greater force production at the higher contraction velocities.

    I thank you for your time in reading this message and would greatly
    appreciate any comments or suggested references.

    Yours sincerely,

    -- Robert Newton Internet:
    Lecturer in Biomechanics ACSnet: rnewton@loki.une.oz
    University of NewEngland,
    Northern Rivers
    P.O. Box 157
    Lismore, NSW 2480 AUSTRALIA
    Phone: +61 (066) 203762
    Fax: +61 (66) 203880