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Paolo De Leva
01-01-2008, 10:02 PM
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 2.4 liter 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"?


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_http://www.timesonline.co.uk/tol/sport/more_sport/athletics/article3075840.ec
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(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