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Isokinetics and Inverse Dynamics

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  • Isokinetics and Inverse Dynamics

    Hello all,

    On my PhD studies I tested top level sprinter, Portuguese and African
    athletes training in Portugal. Average result on 100 m: 10.3 sec.

    They performed MVC on a Biodex isokinetic (isometric and at 30º/s) for EMG
    amplitude normalization.
    Results for one athlete : 350 Nm ( knee isometric peak torque for the
    optimum angle)

    - When tested on the second step after sprint star from block obtained
    maximum concentric net knee joint moments calculated by inverse dynamics of
    around 400 Nm (best athletes).
    EMG Vastus Lateralis -200 % MVC

    - On explosive drop jumps from 25, 40 ,55 and 70cm obtained maximum
    concentric net knee joint moments of 520 Nm. The average jump height was 53
    cm (sd 4.5) for every drop jump height (they performed akimbo) EMG Vastus
    Lateralis -270 % MVC.

    - The GRF where filtered at 15 Hz as suggested by Ton van der Bogert, in
    order to remove the effects of passive impact peaks (nevertheless we do not
    accepted the trials were a clear heel impact occurred.

    It is my conviction that three mechanisms should be responsible for this
    results:

    1- Inhibition on performing MVC isometric contractions. (as suggested by
    Wickiewicz, T.L. et all. Med.Sci.Sports Exerc. 14 144, 1982 and Perrine &
    Edgerton. Med.Sci.Sports 10 159-166, 1978)

    2- On supra maximal stretching-shortening cycles like on the DJ's a
    elastic energy utilization and simultaneously reflex potentiation (neural
    input). as suggested by Komi and co-workers.

    3 Finally the mechanics of multy body kinetic chains that result on the
    transfers of power from segment to the adjacent through the joint (were
    bi-articular muscles could play and important role) Van ingen Schenau,
    Bobbert and co-workers etc.)

    I think that the results that we obtain were consistent with similar results
    on the literature, and point out the limitations of some isometric and
    isokinetic strength test for prediction of actual performance on power
    athletes

    Best regards

    António Veloso
    Biomechanics Lab.
    Faculty of Human Movent Sciences
    Technical University of Lisbon
    Estrada da Costa, 1499 Lisboa Codex.
    Portugal
    Tel: + 351 21 4149127
    Fax: + 351 21 4149129
    Email: apveloso@mail.telepac.pt









    Hello all,On my PhD studies  I tested
    top level sprinter, Portuguese and Africanathletes training in Portugal.
    Average result on 100 m: 10.3 sec.They performed MVC on a Biodex
    isokinetic (isometric and at 30º/s) for EMGamplitude
    normalization.Results for one athlete : 350 Nm ( knee isometric peak torque
    for theoptimum angle)- When tested on the second step after sprint
    star from block  obtainedmaximum concentric net knee joint moments
    calculated by inverse dynamics ofaround 400 Nm (best athletes).EMG
    Vastus Lateralis -200 % MVC- On explosive drop jumps from 25, 40 ,55 and
    70cm obtained maximumconcentric net knee joint moments of 520 Nm. The
    average jump height was 53cm (sd 4.5) for every drop jump height (they
    performed akimbo) EMG VastusLateralis -270 % MVC.- The GRF where
    filtered at 15 Hz as suggested by Ton van der Bogert, inorder to remove the
    effects of passive impact peaks (nevertheless we do notaccepted the trials
    were a clear heel impact occurred.    It is my conviction
    that three mechanisms should be responsible for
    thisresults:    1- Inhibition on performing MVC
    isometric contractions. (as suggested byWickiewicz, T.L. et all.
    Med.Sci.Sports Exerc. 14 144, 1982 and Perrine &Edgerton. Med.Sci.Sports
    10 159-166, 1978)    2- On supra maximal
    stretching-shortening cycles like on the DJ's aelastic energy utilization
    and simultaneously reflex potentiation (neuralinput). as suggested by Komi
    and co-workers.    3 Finally the mechanics of multy body
    kinetic chains that result on thetransfers of power from segment to the
    adjacent through the joint (werebi-articular muscles could play and
    important role) Van ingen Schenau,Bobbert and co-workers etc.)I
    think that the results that we obtain were consistent with similar resultson
    the literature, and point out the limitations of some isometric
    andisokinetic strength test for prediction of actual performance on
    powerathletesBest regardsAntónio VelosoBiomechanics
    Lab.Faculty of Human Movent SciencesTechnical University of
    LisbonEstrada da Costa, 1499 Lisboa Codex.PortugalTel: + 351 21
    4149127Fax: + 351 21 4149129Email: apveloso@mail.telepac.pt

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