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kirtley24
01-16-2008, 10:35 AM
I see Pistorius is appealing the IAAF decision:
http://www.theaustralian.news.com.au/story/0,25197,23063851-2722,00.html

I still wonder about these statements in the report:

- The positive work, or returned energy, from the prosthetic blade is close
to *three times higher* than with the human ankle joint in maximum
sprinting.

- The energy loss in the prosthetic blade was measured at 9.3% during the
stance phase while the average energy loss in the ankle joint of the able
bodied control athletes was measured at 41.4%. *This means that the
mechanical advantage of the blade in relation to the healthy ankle joint of
an able bodied athlete is higher than 30%*.
How is it possible to measure "returned energy" in a
normal foot/ankle? Absorption of energy is straightforward, and it's obvious
that any subsequent positive energy from a prosthesis would have to be
returned energy. Can anyone suggest how it would be possible to seperate how
much energy is returned in the intact normal foot/ankle from that generated
by the plantarflexors?

Chris

On 1/16/08, Adrian Smith wrote:
>
>
>
>
> The IAAF announcement is at:
>
> http://www.iaaf.org/news/Kind=512/newsId=42896.html
>
> I quote:
>
> - Analysis was carried out by a team of more than 10 scientists,
> including staff from the physiology laboratory of Professor J. Mester
> (Institute of Training Science and Sport Informatics).
>
> - 12 high speed cameras (250 frames per second) were used to record 3D
> kinematics, with another 4 highspeed cameras to observe sagittal plane
> motion
>
> - Force platforms were used to record ground reaction forces and point
> of force application
>
> - Athletes ran the 400m test with a K4 mask to record max VO2. VO2
> testing was also carried out in the laboratory (Wingate and Ramp Test)
> on static bicycles. Blood lactate records were taken regularly
>
> - A 3D scanner was used to record body mass and anthropometric measures
> of all the control athletes
>
> - The prosthetics were also subjected to material testing
>
> ---------
>
> The objective results of this study are that:
>
> - Pistorius was able to run with his prosthetic blades at the same speed
> as the able-bodied sprinters with about 25% less energy expenditure. As
> soon as a given speed is reached, running with the prosthetics needs
> less additional energy than running with natural limbs.
>
> - Once the physiological potential of Oscar Pistorius and the
> able-bodied control athletes had been estimated, using three different
> methods, it is clear that Pistorius' potential was not higher than that
> of the controls, even though their performance results were similar.
>
> - The biomechanical analysis demonstrated major differences in the
> sprint mechanics used by a below-knee amputee using prosthetics when
> compared to athletes with natural legs. The maximum vertical ground
> reaction forces and the vertical impulses are different in a highly
> significant way and the amount of energy return of the prosthetic blade
> have never been reported for a human muscle driven ankle joint in sprint
> running.
>
> - The positive work, or returned energy, from the prosthetic blade is
> close to three times higher than with the human ankle joint in maximum
> sprinting.
>
> - The energy loss in the prosthetic blade was measured at 9.3% during
> the stance phase while the average energy loss in the ankle joint of the
> able bodied control athletes was measured at 41.4%. This means that the
> mechanical advantage of the blade in relation to the healthy ankle joint
> of an able bodied athlete is higher than 30%.
>
> "It is evident that an athlete using the Cheetah prosthetic is able to
> run at the same speed as able bodied athletes with lower energy
> consumption. Running with prosthetic blades leads to less vertical
> motion combined with less mechanical work for lifting the body. As well
> as this, the energy loss in the blade is significantly lower than in the
> human ankle joints in sprinting at maximum speed. An athlete using this
> prosthetic blade has a demonstrable mechanical advantage (more than 30%)
> when compared to someone not using the blade.
>
> "IAAF Council has been able to review the full report and has decided
> that the prosthetic blades known as "cheetahs" should be considered as
> technical aids in clear contravention of IAAF Rule 144.2. As a result,
> Oscar Pistorius is not eligible to compete in competitions organised
> under IAAF Rules.
>
>
>
> -------
>
> Adrian Smith
> Headingley UK
> +44 (0)113 3435531
>
>
> -----Original Message-----
> From: * Biomechanics and Movement Science listserver
> [mailto:BIOMCH-L@NIC.SURFNET.NL] On Behalf Of Rodger Kram
> Sent: 15 January 2008 21:49
> To: BIOMCH-L@NIC.SURFNET.NL
> Subject: [BIOMCH-L] Bruggemann report
>
> I have tried in vain to find the Bruggemann report on Oscar Pistorius
> and elastic energy storage in his prosthetic legs.
>
> Can anyone provide a link?
>
> I'd like to discuss the findings that have been leaked to the press but
> I think that as a scientist it is only fair to wait and read the full
> report.
>
> thanks
> Rodger Kram, Ph.D.
> Locomotion Lab
> Integrative Physiology Dept.
> University of Colorado, Boulder
> USA
> rodger.kram@colorado.edu
>
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>



--
Dr. Chris Kirtley MB ChB, PhD
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