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lli92
05-23-2007, 01:19 AM
Hi all,

I have been reading this discussion with fascination.

I will leave the ethical issues to the experts in that area and share some
of my thoughts on the biomechanics aspects of the discussion. Energy and
power production have been discussed. Energy discussion has included the
limitation of the absolute supply of energy and the matter of efficiency.
The power issue has spread from the amount of power production and
distribution of power among different joints. Of course, these two issues
were correlated when discussing efficiency or effectiveness. Prosthesis has
lesser mass has been mentioned as a potential advantage during sprinting.

To my limited knowledge about sprinting, seems like bring the leg forward
faster during swing phase is equally important, if not more important,
comparing to the propulsion during the stance phase. To this end, the lesser
mass of the prosthesis could provide a huge mechanical advantage to the
sprinters. The limited hip joint flexion power is one of the bottlenecks for
increasing sprint speed due to the limited capacity of accelerating the
lower extremity forward at the beginning of the swing phase. Does anyone
have data that comparing the stride frequency and / or the angular
acceleration at the initiation of the swing phase between amputees and none
amputees? I suspect such data might show the amputee sprinters swing their
leg forward faster with greater initial acceleration.

As many have pointed out, sprinting is a process of optimizing the system to
produce fastest speed in a short time. In this process, being able to bring
one's leg forward faster might be one of the most important factors to
improve speed.



Li Li, Ph.D.
Department of Kinesiology
Louisiana State University
112 Long Field House
Baton Rouge, LA 70803
225-578-9146 (phone)
225-578-3680 (Fax)
lli3@lsu.edu