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nanny-rosy
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Author Topic: What if Vibram made the forefoot TPU instead of EVA for the running models?  (Read 1580 times)
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acc
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« on: March 08, 2012, 11:55:21 PM »

Many running shoes use TPU or branded compounds with elasticity in the forefoot to enhance spring. VFFs have EVA throughout the midsole (albeit thin EVA).

Where did I get this idea? (  "Barefoot on unfamiliar textured terrain is a challenge in itself.  You can go more reckless in shoes too as you can get away with flying down the hills, and which is a good thing in a race.  The Newtons are different as they are not traditional soft foam, but rather a firm TPU membrane with recoil properties.  To me this enhances efficiency, and does not sap it away like traditional EVA." - http://naturalrunningcenter.com/2011/09/18/winning-air-force-marathon-natural-running-centers-dr-mark-cucuzzella-44-238/)

What if someone took a Komodosport insole and cored out some of the forefoot to simply induce 1-2mm drop? The footbed is 3mm polyurethane according to Vibram for both the Komodosport, Spyridon, Seeya, and Bikila, so there could be some weight reduction for either of them (meanwhile the Trek/classic soles have EVA insoles as well as the Speed). The Komodosport would be easier to modify due to the removable footbed.
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« on: March 08, 2012, 11:55:21 PM »

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Jeepman
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« Reply #1 on: March 11, 2012, 10:21:04 AM »

All the rebound you need is naturally contained within the elasticity of your muscles and tendons. Any artificial form will only decrease efficiency. All the so called rebound materials and gimmicks are energy vampires. They consume more energy than they "return". This is already occurring inside your muscles, why would you want to add another system in place to go through another energy transformation to lose more efficiency? Any material contained in the soles of VFFs is there for protection and not for "springback". Vibram understands this. Focus more on running form and not so much on gimmicky band aids. There are no perpetual motion machines. Anytime you add another system, you will always lose efficiency.
« Last Edit: March 11, 2012, 10:23:27 AM by Jeepman » Logged

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« Reply #2 on: March 12, 2012, 10:04:38 PM »

But doesn't EVA foam dampen forces more than TPU?

The spring constant of TPU would be stiffer and this there would be less loss. It wouldn't be as stiff as barefoot though (zero loss).

There is conservation of energy at work in all of this: less energy being used to compress foam/rubber/etc.
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« Reply #3 on: March 14, 2012, 05:51:48 AM »

All the rebound you need is naturally contained within the elasticity of your muscles and tendons. Any artificial form will only decrease efficiency. All the so called rebound materials and gimmicks are energy vampires. They consume more energy than they "return". This is already occurring inside your muscles, why would you want to add another system in place to go through another energy transformation to lose more efficiency? Any material contained in the soles of VFFs is there for protection and not for "springback". Vibram understands this. Focus more on running form and not so much on gimmicky band aids. There are no perpetual motion machines. Anytime you add another system, you will always lose efficiency.

Sounds a bit dogmatic to me.  You are not necessarily adding another energy transformation, just a longer compression and rebound.

The calf only rebounds in the neighborhood of 30% of the energy from it's stretching motion.  A mechanical spring or elastic material could be far more efficient.

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« Reply #3 on: March 14, 2012, 05:51:48 AM »

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« Reply #4 on: March 14, 2012, 09:27:48 AM »

All the rebound you need is naturally contained within the elasticity of your muscles and tendons. Any artificial form will only decrease efficiency. All the so called rebound materials and gimmicks are energy vampires. They consume more energy than they "return". This is already occurring inside your muscles, why would you want to add another system in place to go through another energy transformation to lose more efficiency? Any material contained in the soles of VFFs is there for protection and not for "springback". Vibram understands this. Focus more on running form and not so much on gimmicky band aids. There are no perpetual motion machines. Anytime you add another system, you will always lose efficiency.

Sounds a bit dogmatic to me.  You are not necessarily adding another energy transformation, just a longer compression and rebound.
The calf only rebounds in the neighborhood of 30% of the energy from it's stretching motion.  A mechanical spring or elastic material could be far more efficient.

Actually, at "ideal" pace, the calf and achilles will rebound and reuse 50% of the energy it absorbs.  Any material that stands between the foot and the surface is creating a shock absorption buffer zone that reduces the energy transmission.  Springs and elastic are terrible when it comes to the conservation and reuse of energy, that is why shock absorbers are made of these materials. A spring has a home position, the shape of the spring in rest, ultimately the spring wants to return to equilibrium. 

For your achilles to optimize energy return there should be no additional layers of absorption.  I imagine, like many other parts of human anatomy, that the achilles under ideal situations (pure force imparted without the loss due to skin, muscles, and joints) that it would be able to return greater than 50%, but it is limited by other structures.
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