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jwening61
05-17-2007, 02:37 PM
Thank you Dr. van den Bogert for starting this discussion.
As a prosthetist with enough formal biomechanics training
to be dangerous, I am fascinated. Before I provide my
opinion on the topic, I feel a little disclaimer is in
order. I am also a congenital bilateral below knee
amputee. I competed as a swimmer in 3 Paralympic Games (92,
96, 00). Three years ago I started running
recreationally, and currently use prostheses similar to
those used my Mr. Pistorius. Iíve run a few 5k races and
have been as fast as 19:01. So, I will let the membership
of the list decide if my personal experience has placed
undue bias on my reasoning.

First, I get very nervous anytime Ďpurity of sportí is
invoked as a reason to do or not do something. What
constitutes pure sport is very subjective. If we followed
the purity of sport argument to itís logical conclusion,
Olympians should be competing nude in the manner the Greeks
intended. Any new innovation (clap skates in speed skating
that allow an extended push, hatchet blades in rowing that
provide greater purchase on the water, hydrodynamic
swimming suites that increase buoyancy and reduce friction
drag below that of shaved skin, etc.) causes controversy
and drastically alters the nature of the sport, and the
athlete that does not have access to or chooses not to use
this innovation is left behind. Of course this is a
slightly different situation than my examples.

The elite athlete is in a constant process of maximizing
inherent strengths and minimizing inherent weaknesses
through training. So the question is: Is being a bilateral
below knee amputee an advantage that Oscar is attempting to
take maximum advantage of, or a weakness that he is finding
ways to minimize.

While a biomechanical comparison between the amputee runner
and the able-bodied runner is very interesting, I think the
nature of the task is sufficiently different that the
results may not provide enough insight to answer the
question. The cognitive energy alone required to maintain
balance and control on these spring feet may contribute
sufficient advantage to the able-bodied athlete. The
amputeeís hip flexors do a disproportionate amount of the
work compared to the able-bodied. The amputee is not able
to get the prosthetic limb into the same amount of knee
flexion in initial swing as the sound limb. The residual
limb musculature is active to stabilize the limb in the
socket during high level activities. The foot is a spring,
and itís response timing cannot be actively altered or
controlled by the amputee. The ground contact of these
feet is about 25x50mm, so any perturbation in the ground
surface can result in the tibia being thrown in an
unanticipated direction. (I assure you trail running is
quiet the adventure with two of these feet, and almost as
tiring cognitively as physically.) Because of the vertical
compression of the foot, clearance of the contralateral
limb is challenging; there are often hints of circumduction
during swing in the bilateral BK runner, (a biomechanical
inefficiency).

I think one way to assess whether Oscar has an unfair
advantage to use physiologic measures. Is it possible to
make the argument that an able-bodied runner undergoes a
certain metabolic and physiologic cost (oxygen consumption,
lactic acid production, heart rate, etc.) to travel some
unit distance at some unit speed at some level of
biomechanical efficiency? They will then recover that cost
at a certain rate, with better trained athletes recovering
more rapidly. If we can assume that all elite trained
athletes have found a way to near optimize their
biomechanical efficiency, then if the metabolic and
physiologic cost to Oscar is much lower for the same
distance and speed, and he recovers faster than his
able-bodied peers, can we say that he has superior
biomechanical advantage? If it can be shown that he is
trained at a lower physiologic standard than the
able-bodied athletes then the prostheses must be making up
the difference. Iím sure there is someone on the list who
can say if this argument is reasonable.

Finally I would suggest that if there is such biomechanical
advantage, why is Oscar the only bilateral amputee runner
in this situation. He is certainly not the first bilateral
amputee to run on these types of feet. Tony Volpintest was
breaking amputee running records on similar feet in 1992.
I think his uniqueness says much about the difficulty of
the accomplishment.

In the end, as long as leg length is controlled
appropriately, I think the burden of proof must be on those
governing track and field to show unfair advantage, not on
the athlete to show a lack of advantage.

thank you,

jason


Jason Wening, MS, CP
Clinical Research Director
Certified Prosthetist
Scheck and Siress Prosthetics, Orthtoics, & Pedorthics
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