Re: Pistorius - “a considerable advantage”?

[Guest guest]

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.

=========================

I was intrigued that they quote Bruggemann as saying:

" The prosthetics return 90 per cent of the impact energy, compared to

the 60

per cent of the human foot. "

I wonder what people think about that statement - are there any

studies to

back up the 60% figure for normal running? It seems very high to me.

Chris

PS: I do wish news reports would call artificial limbs 'prostheses'

instead

of 'prosthetics' :-)

============================

Carruthers

Wakefield, UK

[Guest guest]

Here's a press release from the International Paralympic Committee (IPC)

regarding the

recent report from the IAAF:

> Subject: IPC Position Statement on IAAFs Commissioned Research on

Pistorius

> From: Press-Releases@...

>

>

> The International Paralympic Committee (IPC) offers the following position

statement in

light of the recent media attention generated by a scientific study initiated by

the

International Association of Athletics Federations (IAAF) that reports that

sprint

performance with Cheetah prostheses offers clear mechanical advantages compared

to the

sprint performance of able-bodied athletes who are capable of similar levels of

performance.

>

> · As a Paralympic Athlete, South African Pistorius is seeking a new

competitive

horizon and these aspirations have propelled him into competition with some of

the

fastest athletes in the world.

>

> · The IPC is highly supportive of 's superb achievement as an elite

athlete, an

attribute he shares with many Paralympic athletes who compete at the highest

levels of

sporting excellence. We also recognize the right of and all other athletes

to question

the rules and regulations that impact their performance.

>

> · In July 2007, the IAAF invited to undergo biomechanical and exercise

physiological analysis, in an effort to collect scientific data on the impact of

prosthetics on

athlete running performance and to assess whether their use contravenes used

IAAF

competition rule 144.2 which prohibits the use of technical aids by athletes

during

competition.

>

> · The tests held on 12 to 13 November 2007 at the German Sports University in

Cologne,

Germany, were commissioned by the IAAF. The IPC was not involved in the research

project.

>

> · After receiving and reviewing the official report, the IPC acknowledges the

scientific

validity of the tests conducted and the outcome of the research project.

However, the use

of an assistive device should not only be considered in solely biomechanical

terms. It is

recommended that further investigations take into consideration other aspects

such as an

examination of the energy loss or generation of the corresponding knee and hip

joints as

well as the impact of the amputation site contact with the prostheses.

>

> · The IPC acknowledges the autonomy of the IAAF to interpret and make

decisions

impacting their federation's competitions based on their initiative to obtain

these results.

> · Furthermore, the IPC recognizes that each International Sport Federation has

the right

to define the eligibility and sport equipment rules governing its competitions,

including

the Olympic Games, to ensure fair competition for all athletes.

>

> · However, equipment plays a critical role in many sports. Equipment evolves

and it is

the responsibility of international federations like the IPC and the IAAF to

stay abreast of

these developments. Rules, regulations and performance standards must be

developed to

ensure that equipment is safe, fair and universally accessible for athletes to

achieve

standards of excellence.

>

> · The IPC is seeking to further collaborate with all relevant parties to

ensure that the

right approach is taken to establishing rules and regulations that promote fair

competition

including with regard to the application of sports equipment.

Just a reminder, the text above was published by the International Paralympic

Committe,

not me. I don't consider myself informed enough to hold an informed opinion on

this

topic.

Regards,

s

Ardmore, PA