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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