Supertraining

Hello Ken,


In a message dated 6/24/09 1:05:07 PM, [EMAIL PROTECTED] writes:


> 
> 
> I ask because lower vertical thrust with comensurate less aerial time
> would
> seemingly require greater horizontal speed to cover the same distance
> (range) both each stride and summative displacement.
> This in turn implies that greater horizontal thrust must be delivered by
> the prothesis relative to each stride or at least a longer impulse to
> effet
> the accelleration from the thrust and this might be deduced from the
> longer
> ground contact time.
> 
> Check out figure 1 in the study. Horizontal 'thrust' is a lot lower in
> Pistorius. This goes back to the bouncing ball analogy. I believe it was
> also the rationale for not including horizontal forces in JAP 2000.
> 
> So then, less metabolic cost with greater efficiency of motive force in
> the horizontal plane requiring less aerial time and less swing frequency
> would seem (at firt blush to me without actually doing the exact figures
> on a
> first approximation) to argue for a clear advantage to the disadvantaged
> runner. And the 17% lower metabolic cost seems to indicate the advantage
> is
> best evidenced over the race of choice, the 400 meters!
> 
> It seems as if horizontal efficiency is not a good way to think about 
> these
> issues since the horizontal work is nearly zero. If there is pretty close
> to zero work, then efficiency must be nearly zero as well. Almost all the
> metabolic energy is incurred to put forces on the ground. As a result, I
> don't know if horizontal efficiency is all that meaningful, even if it
> could be quantified.
> 

Well, theoretically (and disregarding air resistance, internal resistance 
of the moving parts and   thermal effects of the operating mechanism) no work 
at all is needed to maintain a steady horizontal rate of travel!   Of 
course that is not true in practical apps but I agree the work needed to 
maintain 
a given velocity is not a large factor.   That was not my conjecture.

Now to accelerate to a terminal velocity requires a good deal of work and 
you don't get a horizontal acceleration from vertical forces.   Of course the 
runner puts the force to the ground but that force has both a vertical and 
a horizontal component; the vertical component does not accelerate nor does 
it maintain horizontal motion.   The vertical component simply supports the 
runner and gives the vertical acceleration necessary to achieve "air time" 
thereby achieving allowance for   leg cycle 
and determining the aerial time for horizontal travel without ground 
impact/interferrence. The longer this time in the air the less horizontal 
velocity 
necessary to cover a given horizontal distance each stride. This will not 
lead to high overall velocities of course and a maximal solution for velocity 
must be found in trade off of these factors.   Exactly why there is an 
optimum solution that dooms most of us to be genetically not destined to become 
world class runners......... :)

That tests show a lower horizontal thrust component for Pistorius (under 
acceleration or at terminal speed ?) at a given velocity implies that he is 
indeed more efficient; experiences less losses due to the resistances 
mentioned above during the speed maintenance portion of the race.   At anything 
over 
a short sprint, maintenance is the name of the game not acceleration; 
right?   

Greater impulse (thrust) can also be generated by greater contact time 
rather than with greater force.   The tests show greater ground contact time 
for 
Pistorius during acceleration or maintenance or both?   Impulse is the 
product of force and the time of force application and results in a change in 
momentum or counters (in this case) a loss of momentum during motion.   

The bicycle comes to mind as an analogy once again.   With the bicycle, as 
with the prosthesis, there is no outside energy source besides the 
rider/operator.   The bicycles has a very long (continuous) contact time for 
delivery 
of ground forces with no air time to contend with and of course its rolling 
resistance is low. The bike relies on its structure and elastic properties 
of the frame to support and contend with any vertical forces required over 
the terrain. Initial acceleration on a bicycle is hard pressed to compare to 
that of a runner but the increased efficiencies and inherent principles 
utilized in support and ground force application to maintain a given velocity 
are clear advantage for a biker in all but very short races.

I keep coming back to the lower metabolic cost for Pistorius.   How do you 
explain that finding without an inherent increased efficiency in the 
mechanism of his propulsion?? Less oscillating mass in the limbs is one 
probable 
source of increased efficiency (and only one of the possibilities).   Or are 
you saying that Pistorius is "special" and if that is the case then the study 
should continue to detemine a measurement of his metabolic cost to "run" a 
course on the upper body ergonometer to establish 
independence from the prosthesis.   Were he to show increased efficiencies 
over the other "runners' on such a device then his clear superiority as an 
athlete would be established and in his case alone anadvantage conferred by 
the prosthesis might be discounted.   (If I recall correctly, didn't one of 
the investigations reveal that Pistorius was not as fit cardiovascularly as 
some comparison runners or at least as fit as his potential?   What does that 
imply with regard to the efficiency advantage, if any, of the prosthesis?)

Less energy cost with shorter race times and less horizontal force needed 
for maintenance of that velocity achieved with less vertical displacement and 
more ground contact time.   Is that a fair description of the Pistorius 
results?   It is surely a fair description of bicycle transport versus a 
runner, IMHO.

No, I think the ban is justified and the tests confirm it with their 
measurements and results.   Perhaps i am missing something but until there is a 
sanctioned distance race for athletes competing with or without non-powered 
equipment of their choice (sounds like an engineering contest not Olympic 
competition), I think we should ban bikes, wheel chairs, scoot boards, pogo 
sticks, skates/skate boards, stilts, ...........................and all 
prostheses from competing with "unaided" runners.

Now, about those aluminum baseball bats............or the introduction of 
the fiberglass vaulting pole...........or the superslick wet suits being used 
by the world's fastest swimmers, etc.   At least in those cases of 
innovation in athletic gear or equipment, all competitors have or may choose to 
have 
the same "advantage".   Why not establish a prothesis category and define 
and limit it as the rules committee may determine? If those runners break all 
the records then they may still be recognized as the fastest humans alive 
and be awarded medals in their category.   I don't see why they should not be 
allowed to run with (along side) the "conventional" athlete in this 
pursuit!   Should the prothesis equipped athletes prove to be or develope into 
the 
superior runners in the field; they will serve in their winning competitions 
to set a "rabbit" pace for the less accomplished (disadvantaged) 
"conventional" runners to aspire to.

Respectfully,
Paul Boardman
Chicago, USA