

YEAH BUDDY wrote:
Johnny Karate wrote:
Only about a quarter of the energy we burn ends up actually propelling us forward. So at most he would run 1% faster with that extra 4% of energy.
YEAH BUDDY wrote:
Spanish Inquisition wrote:
you're wrong there wrote:
Rockgip wrote:
Efficiency â‰ Time Improvements
Yes, efficiency does equal time improvements.
Yes, but a 4% efficiency benefit will not make you run 4% faster.
Ok right technically it means that you can run at the same speed with 4% less energy but obviously that means you have 4% extra energy which you can use to run 4% faster. Sorry didn't realize I was dealing with a semantics master over here
So where does the other 3% go? Was he going 1% higher? Or was moving to each side 1% more? Sorry bud but I think you may have been talking a little above your level of expertise in the subject
Overcoming air resistance, which hasn't been changed with the shoes.
It's not linear either. Athletic performance doesn't increase linearly. 
Also lots of energy goes into vertical displacement

Take away the drafting runners and you get 2:03:24 for that marathon

YEAH BUDDY wrote:
Spaghettimonster wrote:
Rockgip wrote:
Efficiency â‰ Time Improvements
This is all that needs to be said. Not all equations are linear people.
So then it's possible the 4% more efficient shoes would have made him more than 4% faster??
Let's say they invent a car that uses fuel 10% more efficiently. Does that mean the car will go 10% faster? No. It just means the car uses 10% less fuel to travel the same distance. How that translates to running performance can't really be quantified but no it's probably not 1 to 1 as people are suggesting.
The difference is runners get tired. Cars do not. I imagine when Kipchoge's fresh the extra 4% isn't going to make him run faster at all because his tank is full. However, in the later stages of the race, when he's getting tired and running out of energy, that extra 4% might help him SLOW DOWN LESS than if he were wearing conventional shoes. In the late stages of the race Kipchoge slowed and his rate of slowing increased, but he didn't fall off a cliff. The shoes might have helped there. 
Les wrote:
The difference is runners get tired. Cars do not. I imagine when Kipchoge's fresh the extra 4% isn't going to make him run faster at all because his tank is full. However, in the later stages of the race, when he's getting tired and running out of energy, that extra 4% might help him SLOW DOWN LESS than if he were wearing conventional shoes. In the late stages of the race Kipchoge slowed and his rate of slowing increased, but he didn't fall off a cliff. The shoes might have helped there.
Ok so let me get this straight, the shoes don't work on Kipchoge because his engine is already full? Ok Renato... oh sorry I mean Les 
Hog wrote:
Take away the drafting runners and you get 2:03:24 for that marathon
Wow so drafting adds another 2.8%? So the 2:00:25 is actually worth closer to 2:08:45?! Seems a high but I guess I could believe it... wow that's crazy, just goes to prove how fast 2016 London Kipchoge could have run 
BIG PROBLEM:
4% slower than 2:00:25 is not 2:05:13. 2:05:13 is 104% of 2:00:25.
A different concept entirely.
4 % slower than 2:00:25 is not calculated this way.
You need to find the number that, when 4% is subtracted from it, becomes 2:00:25. 
To further explain, that's like saying that 4% slower than 100 is 104, if we're referring to a 4% reduction resulting in 100. Clearly 96% of 104 is not 100.

Marathonsarecool wrote:
To further explain, that's like saying that 4% slower than 100 is 104, if we're referring to a 4% reduction resulting in 100. Clearly 96% of 104 is not 100.
Interesting because I was under the impression that 1% of 100 is 1. Therefore 4% of 100 is 4. Therefore 4% more than 100 is 104. But I'll be interested to hear what part of that is wrong. 
YEAH BUDDY wrote:
Marathonsarecool wrote:
To further explain, that's like saying that 4% slower than 100 is 104, if we're referring to a 4% reduction resulting in 100. Clearly 96% of 104 is not 100.
Interesting because I was under the impression that 1% of 100 is 1. Therefore 4% of 100 is 4. Therefore 4% more than 100 is 104. But I'll be interested to hear what part of that is wrong.
100/104 = 0.962, not 0.960
Using this same formula, you get 2:05:26, not 2:05:13
(7225 seconds / 0.96)
YOU'VE BEEN MATHED! 
You don't run by your feet bouncing into the air, you run by accelerating your body forward in front of your foot which then pulls it off the ground. A springloaded shoe is as useful as a device to make your arms swing.
If you don't believe me, try to leave your takeoff foot on the ground next time you run. 
That is all correct.
But 4% more than 100, is not the same as a reduction of 4% equaling 100. Which is what your original thesis posited. 
posters need to acquaint themselves with physics
4% more efficient means 4% better energy return
the conversion to speed improvement is using drag equation which is speed^3
> speed increase is :
1.04 ^ ( 1/3 )
=
1.0132
for a 2"00'25, the conversion is :
2"02'00 
thefastestone wrote:
That is all correct.
But 4% more than 100, is not the same as a reduction of 4% equaling 100. Which is what your original thesis posited.
I think my original thesis was that 4% slower than 2:00:25 is 2:05:13. In fact, I'm sure of it. 
Actually all equations ARE linear, at least for small enough displacements. And I'm skeptical that 4% is a large enough change for nonlinearities to be comparable to the firstorder effects. The real point here is that we don't know what the slope of the linear approximation is (or at least I don't).

calculo wrote:
posters need to acquaint themselves with physics
4% more efficient means 4% better energy return
the conversion to speed improvement is using drag equation which is speed^3
> speed increase is :
1.04 ^ ( 1/3 )
=
1.0132
for a 2"00'25, the conversion is :
2"02'00
First, isn't it true that drag is proportional to v^2 at running speeds, not v^3? Second, drag isn't the only, or even primary, limiting factor in running performance, so this is not a valid conversion technique. 
Everyone is saying it's not 4% but is throwing out no sources for their shotinthedark alternatives, meanwhile Nike has done hard research and spent a ton on this thing so I'm sorry peanut gallery but I'm going to have to go with the science on this one

YEAH BUDDY wrote:
Not too impressive when you think about it that way...
so you think Eluid is in 2:05:13 shape rn?....lolololol 
YEAH BUDDY wrote:
I'm going to have to go with the science on this one
Nope. Funding bias, not science.