No announcement yet.

Re: Oscar Pistorius has "a considerable advantage"?

This topic is closed.
  • Filter
  • Time
  • Show
Clear All
new posts

  • Re: Oscar Pistorius has "a considerable advantage"?

    The below may be of interest:

    Taken from:

    A. J. Blazevich and N. C. C. Sharp
    Sport Sciences, Brunel University, Uxbridge, UB8 3PH, UK

    In order for a human to run quickly and efficiently for a given
    period of time a number of physiological, biochemical and
    biomechanical processes must be optimised. Human running is
    accomplished by performing a series of bounces as gravitational
    energy is stored in our `leg springs' during the leg shortening, or
    impact, phase and is released during the leg lengthening, or
    propulsion, phase (Fig 1). Approximately 0.6 J of energy are stored
    and released per kilogram per bounce in the foot and calf (Ker et al.
    1987), compared with about 1.1 J per kg in a 0.5 ton horse (Minetti
    et al. 1999). The total energy stored and released in the whole leg
    represents a substantial portion (about half in humans) of the energy
    required to propel the body into the next step. Because the highly
    elastic (ie high energy return) tendons are most responsible for this
    spring-like behaviour, and their properties change in response to
    loading, it is reasonable that some portion of training should target
    the tendon..........

    The remaining energy required for running must come from muscle
    contraction. It has been held traditionally that muscles lengthen, or
    work eccentrically, during the impact phase of running and shorten,
    or work concentrically, during the propulsive phase. Recent evidence
    from human research, and experiments on animals, shows however that
    muscles contract quasi-isometrically during the propulsive phase of
    many stretchshorten- type movements (eg Kurokawa et al. 2003), or
    during high-speed movements performed without a counter-movement
    (Kurokawa et al. 2001). This makes sense when one considers the work
    of Hill (1938), who showed that concentrically-contracting muscle
    uses more energy than isometrically-contracting muscle, with the
    disparity increasing as muscle force or length change (or velocity)
    increased. As muscle power increases, the relative cost of performing
    work by concentric muscle action increases, and the benefit of using
    stored energy becomes greater.

    The spring in the arch of the human foot.

    Nature. 1987 Jan 8-14;325(7000):147-9.

    Ker RF, Bennett MB, Bibby SR, Kester RC, Alexander RM.
    Large mammals, including humans, save much of the energy needed for running
    by means of elastic structures in their legs and feet. Kinetic and potential
    energy removed from the body in the first half of the stance phase is stored
    briefly as elastic strain energy and then returned in the second half by
    elastic recoil. Thus the animal runs in an analogous fashion to a rubber ball
    bouncing along. Among the elastic structures involved, the tendons of distal leg
    muscles have been shown to be important. Here we show that the elastic
    properties of the arch of the human foot are also important.

    Jamie Carruthers
    Wakefield, UK