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

    Thanks Paolo, and Happy New Year to everyone!

    I wondered if we could focus this discussion on how you could possibly go
    about measuring energy return? Has it been done, or are Bruggemann's figures
    just guestimates?

    I suppose a power (energy) flow analysis could tell you how much energy is
    absorbed at the ankle, but I can't see how you could know how much is
    usefully returned. Can anyone suggest how it might be done?

    Chris




    On Jan 2, 2008 7:02 PM, Paolo de Leva wrote:

    > It is difficult to discuss about a scientific report without reading it.
    > The article on The Times is a non-scientific popularized summary. It may
    > distort Bruggemann's conclusions and disregard important parts of his
    > analysis. However, the conclusion suggested by the article seems strongly
    > biased to me.
    >
    > I wonder why there's no mention in the article about the chemical energy
    > transformed by calf muscles into mechanical energy, which is a
    > non-negligible n% for non-amputee athletes, and 0% for Pistorius. In other
    > words Pistorius's prostheses are passive, while non-amputees shanks and
    > foots are endowed with extremely powerful actuators.
    >
    > I also wonder whether the advantage of having shanks and foots during the
    > first part of the sprint is taken into account. In this phase of the race,
    > the needed mechanical energy is almost totally produced by transforming
    > chemical energy (ATP hydrolysis powering myosin bridges in sarcomeres),
    > rather than using stored elastical energy. Thus, the mechanical energy
    > produced by active shortening of sarcomeres in the triceps surae is much
    > more important than that returned by the series elastic elements of the same
    > muscle. And Pistorius possesses an "incomplete" engine, when compared with
    > non-amputees. In other words, Pistorius's prostheses do not have a
    > contractile component.
    >
    > If a Formula 1 car were powered by a 2.2 liter engine rather than a 2.4liter engine (less powerful actuator), and with 6 wheels, rather than 4
    > (more efficient passive component, perhaps?), and you were asked to compare
    > its performance with that of a standard Formula 1 car, would you only focus
    > on the (possible) advantage associated with the additional wheels?
    >
    > Moreover, Pistorius's aerobic performance was found to be worse. I wonder
    > whether it was taken into account that non-amputees use the triceps surae to
    > burn part of the oxygen?
    >
    > I am not maintaining that the advantages prevail over the drawbacks. I
    > just suggest to consider both and not to underestimate the complexity of the
    > problem.
    >
    > With regards,
    >
    > Paolo de Leva
    >
    >
    > -----Messaggio originale-----
    > Da: * Biomechanics and Movement Science listserver [mailto:
    > BIOMCH-L@NIC.SURFNET.NL] Per conto di Jamie S. Carruthers
    > Inviato: sabato 22 dicembre 2007 11.14
    > A: BIOMCH-L@NIC.SURFNET.NL
    > Oggetto: Oscar Pistorius has "a considerable advantage"?
    >
    >
    > Members may be interested in:
    >
    >
    > _http://www.timesonline.co.uk/tol/sport/more_sport/athletics/article3075840.ec
    > e _
    > (
    > http://www.timesonline.co.uk/tol/sport/more_sport/athletics/article3075840.ece
    > )
    >
    >
    > Report delivers premature blow to Olympic hopes of Oscar Pistorius
    > Oscar Pistorius, the double amputee sprinter who wants to be allowed
    > to run in the Olympic Games, is given "a considerable advantage" over
    > his able-bodied competitors by his prosthetic blades, the man charged
    > with testing him said yesterday.
    >
    > "He [Pistorius] has a considerable advantage compared with athletes
    > without prosthetic limbs who have undergone the same tests,"
    > Professor Peter Bruggemann told Die Welt, the German newspaper,
    > yesterday before Pistorius had seen his report of the tests. "The
    > difference is several percentage points and I did not think the
    > findings would be so clear.
    >
    > "His aerobic performance was worse, his anaerobic performance was the
    > same. He could be in better shape. The fact that he still runs the
    > same times as the other runners is due to his prosthetics. The
    > prosthetics return 90 per cent of the impact energy, compared to the
    > 60 per cent of the human foot."
    >
    > Bruggemann, the director of the Institute of Biomechanics at the
    > German Sports University in Cologne, last month conducted private
    > tests on Pistorius and six able-bodied athletes who had similar 400-
    > metre times. The IAAF, which commissioned and paid for the tests,
    > received Bruggemann's report on Tuesday and Pistorius became aware of
    > receiving an e-mail with them attached only last night after being
    > contacted by The Times.
    >
    > Bruggemann suggested that the way Pistorius runs is different from
    > able-bodied athletes. "It looks good, smooth, somehow elegant [when
    > Pistorius runs]," Bruggemann said. "It's a totally different kind of
    > movement. He was incredibly co-operative and open. I think most of
    > all he wants to be better and faster. If he continues to improve his
    > stamina, I could imagine him breaking the non-disabled world record
    > over 800 metres."
    >
    > Pistorius will have been shocked by the disclosure of the results
    > because he was not expecting any public announcements until the new
    > year at the earliest. "The IAAF does not plan to discuss the contents
    > of the report, or make any public announcement about any decision
    > related to the report, until January 10, 2008," it said in a
    > statement yesterday. The IAAF has not come to an official verdict,
    > but the decision of the council will be based on Bruggemann's report,
    > so that seems academic.
    >
    > Pistorius, 21, was born without fibula muscles and his legs were
    > amputated below the knee at 11 months old. He has said that he would
    > stop running in able-bodied competition if the tests proved that his
    > carbon-fibre blades called "Cheetahs" by Ossur, the manufacturer
    > gave him an edge. But he did not expect the tests to go against him,
    > saying that if they did, he would seek a second opinion from another
    > set of independent tests.
    >
    > ===================
    > Jamie Carruthers
    > Wakefield, UK
    >
    >
    >
    >
    >
    >
    >
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    >



    --
    Dr. Chris Kirtley MB ChB, PhD
    608 Dockside
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    Australia
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    Clinical Gait Analysis: http://www.univie.ac.at/cga
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