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2nd posting response to: James Dowling

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  • 2nd posting response to: James Dowling

    Due to a large number of requests for the reference list to my prior
    message I am re-posting the message with the references listed. The Walshe
    et al. paper I was referring to in the previous posting was actually 1998
    instead of 1997 which I stated. I apologize for this mistake.

    James Dowling wrote:
    >Without entering the weights vs machines debate, I think it is important
    >to clear up a fallacy that may be widely accepted in the athletic training
    >community regarding the measurement of the utilization of stored elastic
    >energy in human movement.

    I do not know to which fallacy you are referring in the athletic
    training community (exercise science community). You are discussing two
    different issues in your e-mail. The first question is that of the use of
    stored elastic energy in human movement. I would refer you to a recent
    investigation by Witte et al. 1997. This investigation supplies significant
    evidence that human movement does involve the use of stored elastic energy.
    This evidence was from in vivo measurements not computer modelling.

    The second question is to why their is a difference in jump height
    between a countermovement and static jump. It appears that stored elastic
    energy may not be responsible for the difference observed in jump height as
    supported by a recent investigation (Walshe et al. 1998). However, the
    authors in this investigation still could not state with complete confidance
    that stored elastic energy did not play a role. In addition, one
    investigation using a musculoskeletal model has suggested that significant
    levels of potential energy are stored and utilised during a countermovement
    jump and that the contractile elements of the muscle perform more total work
    during a static jump (Anderson and Pandy 1993).

    Irrespective of this I am skeptical of computer or mathematical
    models when spring constants for the elastic potential of skeletal muscle
    are derived from single muscle fibres in vitro. Is this representative a
    whole muscle in vivo? The muscle protein titin, which is one of the key
    players in muscle elasticity was not even completely sequenced until 1995
    (Labeit and Kolmerer). In addition, the elastic potential of titin was not
    clearly observed until 1997 (Kellermayer et al.). Witte et al. 1997
    suggests through recent analysis that the muscle tissue itself is most
    likely contributing to a large portion of useable stored elastic energy in
    human movement. More than ever considered in the past. Titin in cardiac
    muscle has been shown to contribute up to 1% of twitch force after stretch
    (Granzier et a. 1997).

    I am curious as to how a computer model can determine the stored
    elastic energy potential of all the skeletal muscle (for example) in the
    thigh musculature. Especially when the quantity and ratio of titin (and
    other possible elastic proteins) in comparison to myosin and actin has not
    been clearly defined. If we do not even know the quantity of titin in the
    thigh musculature then how can a computer model determine the true elastic
    potential of all the muscle involved in a countermovement versus a static
    jump? I do not think there is any fallacy that is widely accepted in the
    exercise science community. I think this issue still needs substantial
    amounts of additional investigation. The true elastic potential of muscle
    of a highly trained athlete is still unknown and could contribute to
    differences in countermovement and static jump performance. The adaptive
    role of elastic proteins such as titin with exercise has only started to be
    explored (Fry et al. 1997). It is much to early for any final conclusions
    concerning this issue.

    Witte H, Recknagel S, Rao JG, W├╝thrich M, Lesch C (1997) Is elastic energy
    storage of quantitative relevance for the functional morphology of the human
    locomotor apparatus? Acta Anat 158: 106-111

    Walshe AD, Wilson GJ, Ettema GJ (1998) Stretch-shorten cycle compared with
    isometric preload: contributions to enhanced muscular performance. J Appl
    Physiol 84(1): 97-106

    Anderson FC, Pandy MG (1993) Storage and utilization of elastic strain
    energy during jumping. J Biomech 26(12): 1413-27

    Labeit S, Kolmerer B (1995) Titins: Giant proteins in charge of muscle
    ultrastructure and elasticity. Science 270: 293-296

    Kellermayer MSZ, Smith SB, Granzier HL, Bustamante C (1997)
    Folding-unfolding transitions in single titin molecules characterized with
    laser tweezers. Science 276: 1113-1116

    Granzier H, Kellermayer M, Helmes M, Trombitás K (1997) Titin elasticity
    and mechanism of passive force development in rat cardiac myocytes probed by
    thin-filament extraction. Biophys J 73: 2043-2053

    Fry AC, Staron RS, James CBL, Hikida RS, Hagerman FC (1997) Differential
    titin isoform expression in human skeletal muscle. Acta Physiol Scand 161 :
    Jeffrey M. McBride, MS, CSCS
    School of Exercise Science and Sport Management
    Southern Cross University
    PO Box 157
    Lismore, NSW 2480, Australia
    Telephone: Int + 61 2 6620 3763 Facsimile: Int + 61 2 6620 3880

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