Slow Tracks Vs Fast Tracks

[rainy.here]

The decay term is exponential -- exp(-bt^2) -- so although it is technically correct to say it is "based on" t^2, it's a bit misleading.

True, but I wanted non-math type people to still be able to understand a bit what I meant.

The purpose of that function is to model the initial drive phase of the athlete. The constant b is chosen to fit the observed velocity curves, and as a result its effect largely goes away by about 1 second into the race. Earlier models didn't include it, but did use non-exponential, velocity-dependent decay terms (see e.g. Keller's optimization model). The problem is that the latter produces unrealistic speed curves.

A velocity-dependent term would certainly be well-motivated from a biomechanical point-of-view, as it would more appropriately represent the transition in posture during the early drive (since velocity is a universal determinant in gait-related motion). The flip side of this argument is that during this phase the cross-sectional area of the athlete is smaller than for upright running, and the athlete's velocity is well under 10m/s. So, drag effects are much less important.

I would be surprised if changing that drive term would alter the results in any significant way (for the averaged winds). But that being said, one could always investigate it. It would be a relatively easy thing to check out. If you're up to it, email me.

I too would be surprised if changing the model would have much effect on the averaged wind speeds, but your results in the discussion of how different wind curves during the race will effect the final time didn't make much sense to me intuitively, and that was the first possible change that occurred to me, though there was another one I can't remember right now . I might have time to investigate this fall when I'm unemployed, but the ski hill hasn't opened yet.

[JRM]

The decay term is exponential -- exp(-bt^2) -- so although it is technically correct to say it is "based on" t^2, it's a bit misleading. The purpose of that function is to model the initial drive phase of the athlete. The constant b is chosen to fit the observed velocity curves, and as a result its effect largely goes away by about 1 second into the race. Earlier models didn't include it, but did use non-exponential, velocity-dependent decay terms (see e.g. Keller's optimization model). The problem is that the latter produces unrealistic speed curves.

A velocity-dependent term would certainly be well-motivated from a biomechanical point-of-view, as it would more appropriately represent the transition in posture during the early drive (since velocity is a universal determinant in gait-related motion). The flip side of this argument is that during this phase the cross-sectional area of the athlete is smaller than for upright running, and the athlete's velocity is well under 10m/s. So, drag effects are much less important.

I would be surprised if changing that drive term would alter the results in any significant way (for the averaged winds). But that being said, one could always investigate it. It would be a relatively easy thing to check out. If you're up to it, email me.

[eldrick]

it's a pleasure to read such quality posts

proferring a suggestion until if/when jrm explains it to us :

the decaying force is a mass*acceleration quantity

a = v/t = ( s/t )/t = s/(t^2)

is jrm perhaps reducing the variables to the most basic parameters of s & t & bypassing v ?

[rainy.here]

....to put an end to it: I've seen several projections/calculations from you that in the face of reality and logic conflictingly does not reflect Bolt's edge or give him such when due. Or you seem to always have answer as why a poster is wrong about a lofty supposition of Bolt.

Your calculations are often subjective

You often use Statistics in place of physics to answer problems of physics...

but anyway loop to the top and join me a quest to find a competent head for the problem at hand, we can take up your misgivings on a another thread dedicated to them.

You need to be considerably more specific (than not at all) in your criticism of his calculations if you want to convince people or be taken seriously. If you're correct, you're certainly doing a piss poor job of demonstrating it. While I have a couple issues with his 100m wind/altitude adjustment paper, and I think he's made a couple small mistakes, they are not at all relevant to the calculations themselves (in my opinion), but to the discussion that follows the model. I'll give you an example to show you what I mean by being specific:

JRM uses equation (4) to determine the decay in driving force as the race progresses, and is based on t^2. I think this is a mistake, and should be based on some power of v. While it will have very little effect (if any) on the overall calculations, I think it (among other assumptions used in the model) changes or invalidates the implications later in the paper of how different wind speeds at different parts of the race, each which will have the same average, can have different effects on the overall time.

[eldrick]

Eldy, my friend,
I actually have no doubts about the anatomy or the physiology of human performance. Having coached distance runners from the school level to the Olympic finals, I know that there is NO correlation table which can accurately predict an individual athlete's performance, from one event to the next.

i beg to differ

try this ( but obviously you need 2 inputs - a 400m time will do nicely, providing it is accurate & best possible )

http://www.jundo.co.uk/

i have tried a few thousand calculations on it & applying some commonsense to it, it's never been wrong

Having said that, I think it's good "background" data to help coaches and athletes, but it is individual anatomy and physiology and psychology that are the "foreground" factors for determining performance. I will concede that once you get events that are proximate in distance, and involve similar energy systems, then predictions are more possible, but still theoretical. Fun to play with, for some, but not to be taken as gospel truth.

give us a 1500, 3k, 5k or 10k guy/gal & tell me his absolute best 400 time & 800 time from formal flat-out training runs ( accurately as possible timed ( add 0.14s for HT ) & with wabbits for 800 ) just prior to running on the circuit & it'll tell you how fast they are capable of running for their speciality distance that year - & no faster than that - it takes the mystery out of it, but you'll get the best answer possible

( for 800 guys you can use a 400 & 600 )

As for energy returns from tracks, I have done some consulting in that area also, so I understand the differences. But I come back to the fact that different athletes are still a "work of one", when assessing performances and potentials. Or maybe a "work of two", if they are well coached....

that anatomy/physiology query you have boils down to their efficiency as machines to convert PE to KE

as we are talking elites here with 10.00/1'43.00/3'30/13'00/etc, by inference they are likely to be extremely efficient machines with optimal cadence, foot-strike, etc & i think you can be reassured they are energy convertors of a similar very high standard ( albeit of course never 100% due to friction, heat-generation, etc )

[rasb]

...I just think human physiology and anatomy are much more complicated than that. I could be wrong.....I was once

they are not actually ( within small ranges )

i can offer you a proxy

a 4'01 gal ( in training in her book ) runs 8'22 on the circuit

she has never run a flat-out 10k at that point, but it's extrapolated to ~ 30-flat - see what she runs in munich

all the same doubts you have about anatomy/physiology, etc, you have are also inherent in above extrapolation, but it gave us the correct number

same with energy return in tracks if we get the detailed analysis/method

Eldy, my friend,
I actually have no doubts about the anatomy or the physiology of human performance. Having coached distance runners from the school level to the Olympic finals, I know that there is NO correlation table which can accurately predict an individual athlete's performance, from one event to the next. Having said that, I think it's good "background" data to help coaches and athletes, but it is individual anatomy and physiology and psychology that are the "foreground" factors for determining performance. I will concede that once you get events that are proximate in distance, and involve similar energy systems, then predictions are more possible, but still theoretical. Fun to play with, for some, but not to be taken as gospel truth.
As for energy returns from tracks, I have done some consulting in that area also, so I understand the differences. But I come back to the fact that different athletes are still a "work of one", when assessing performances and potentials. Or maybe a "work of two", if they are well coached....

[gh]

I'm not telling you again, that's for sure. Take the hint.

[Paul Henry]

Like I conceded Mr. Hill : " Never mind me not being a physicist. The main aim of the physicist is to solve the problem and make it plausible to the non-such."

So it's rather rude to tell me that I'm in over my head.

[Paul Henry]

As JRM said, obviously you know nothing about physics. You're in over your head here PH. Leave it alone.

GH LOOP TO TOP,
SUBJECTIVE IN YOUR DEFENSE I SEE!!!!

[gh]

As JRM said, obviously you know nothing about physics. You're in over your head here PH. Leave it alone.

[Paul Henry]

Point to note: Take it as constructive critique. I have the same comments about the eggheads that said the optimal height for optimum sprinting would not reach as tall as Bolt, But today are saying that the optimum sprinting anatomy/physiology is Bolt's: subjective and an exercise of brain mass that proves nothing and leaves back to square 1 in that debate.

"a child shall lead them" you can brush up on the subjectivity in your work.

P.S. Loop to top

[Paul Henry]

....to put an end to it: I've seen several projections/calculations from you that in the face of reality and logic conflictingly does not reflect Bolt's edge or give him such when due. Or you seem to always have answer as why a poster is wrong about a lofty supposition of Bolt.

So, you've "proven" nothing about the calculator. I'm not sure what other "calculations" I've presented, though.

Your calculations are often subjective

What calculations?

[quote:ar9dxk51]
You often use Statistics in place of physics to answer problems of physics...

Many physicists use statistics in lieu of physics when the situation warrants. I assume you are not familiar with the discipline.[/quote:ar9dxk51]

DING DING DING, Point I'm trying to make about your calculations. Never mind me not being a physicist. The main aim of the physicist is to solve the problem and make it plausible to the non-such. You my friend, are easily uncovered in subjectivity. But please, loop to top?

[eldrick]

jrm

i'd like some advice about the formula i suggested & whether it is offering something useful

it just assumes that increase PE returned is converted to increased KE at 100% ( obviously only a perfect machine does that ) & therefore boils down to ( ratio of PEs )^1/2

obviously we are only talking in small ranges as biomechanical restrictions prevent increasing PE being converted fully to KE

[JRM]

....to put an end to it: I've seen several projections/calculations from you that in the face of reality and logic conflictingly does not reflect Bolt's edge or give him such when due. Or you seem to always have answer as why a poster is wrong about a lofty supposition of Bolt.

So, you've "proven" nothing about the calculator. I'm not sure what other "calculations" I've presented.

Your calculations are often subjective

What calculations?

You often use Statistics in place of physics to answer problems of physics...

Many physicists use statistics in lieu of physics when the situation warrants. I assume you are not familiar with the discipline.

[Paul Henry]

....to put an end to it: I've seen several projections/calculations from you that in the face of reality and logic conflictingly does not reflect Bolt's edge or give him such when due. Or you seem to always have answer as why a poster is wrong about a lofty supposition of Bolt.

Your calculations are often subjective

You often use Statistics in place of physics to answer problems of physics...

but anyway loop to the top and join me a quest to find a competent head for the problem at hand, we can take up your misgivings on a another thread dedicated to them.