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adidas Boost: Some Actual Running Economy Data

Posted on August 15 2013

adidas BoostSeveral months ago when adidas first started to market their new BOOST midsole material they made a big deal of touting the fact that the sole, which is composed of fused polyurethane beads, provides greater energy return than traditional EVA. The implication was that this energy return would provide a performance benefit to a runner by improving running economy (i.e., reducing the work needed to be done by our muscles to get from point A to point B).

I was very skeptical of this marketing approach since there was no physiological data available from actual runners to back up the claims based on mechanical testing. That data now appears to exist. In the June 2013 issue of Footwear Science is an abstract of a study titled “Running shoe cushioning properties can influence oxygen consumption.” The study was carried out by a team from the University of Calgary headed by Jay Worobets.

The study utilized a fairly simple methodology. Twelve runners ran both overground and on a treadmill in shoes with the Boost midsole and in identical shoes with a sole composed of more traditional EVA foam. While running, their oxygen consumption was monitored as a measure of running economy (increased oxygen consumption at a given pace = lower economy).

Results indicated that in both treadmill and overground running the subjects were slightly more economical in the shoes with the Boost midsole (differences were statistically significant). Here are the numbers:

 

O2 Consumption

O2 Consumption

 

 

EVA Shoe

BOOST Shoe

% Difference

Treadmill

44.7 ml/kg/min

44.3 ml/kg/min

0.9%

Overground

40.7 ml/kg/min

40.3 ml/kg/min

1.1%

Though the differences were significant, the actual differences were quite small between the shoes on both running surfaces. Thus, BOOST improved economy by about 1%.

It’s important to keep in mind that the comparison here was between shoes that only differed in their midsole material, everything else was the same. There is no detail about which Boost shoe was used, what the midsole dimensions were, etc. So it’s very difficult to compare economy gained running in a Boost shoe to any other shoe on the market. As an example, previous research has shown that reducing shoe weight by about 3.5 oz (100g) results in an economy improvement of about 1%. So if the shoe used was the 9.3 oz Energy Boost, then it might not be any more economical than say the 5.7 oz adidas Gazelle. The benefit would be that you get the improved economy with additional cushioning in the Boost.

Having run in the adidas Energy Boost shoe myself a few times I also wonder if there is a certain thickness of midsole material required to provide any actual benefit. The Energy Boost has about 9-10mm more material under the heel than under the forefoot. As someone who doesn’t load my heels much when I run, the Boost did not feel all that different to me than a typical EVA shoe. But, if I forced a more pronounced heel strike I could really feel the bounciness that the Boost material provides (you can also feel it when walking in the shoes). My suspicion is that there is simply not enough Boost under the forefoot to provide a meaningful benefit. An Altra Torin or Hoka style Boost shoe would be an interesting thing to try!

So my take is that if you are a heel striker, Boost may provide a bit of an economy benefit for you in a very well cushioned shoe. If you are a midfoot or forefoot striker the benefit will likely not be as noticeable. Different shoes likely work better for different gaits.

As for myself, I actually didn’t enjoy running in the Energy Boost very much because there was too much heel for my taste, and it has a very pronounced heel flare – the sole extends well out from the margins of your heel on all sides. The upper is also too snug for my feet. Personally, I’d opt for a shoe like the adidas Hagio over the Boost for races of half marathon distance or less – lighter, firmer, and stiffer is my preference for speed. But over 26.2 miles I could see some value in a softer sole, and a 4-6mm drop Boost shoe might be something that would pique my interest a bit more as a distance shoe. Boost looks top be permeating the adidas line, so looks like we’ll have more to try out in the coming months!

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