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Reebok's Push Towards a [Ree]Newable Future
Doctors of Running Sustainability Project, Volume 1

By Bach Pham, Social Media Manager

Welcome to the first edition of our Sustainability Project at Doctors of Running! In this long term series, we'll be talking with companies, researchers, and forward-thinkers on the subject of footwear sustainability. In 2019, it was found that over two billion running shoes were purchased in the calendar year. With running shoes as popular as ever, they bring a unique problem as far as waste is concerned. While clothing tends to have ways to breath new life through repair and reuse, footwear currently has a fairly definitive end-of-life. Sustainability, however, has quickly become the focus of footwear brands in the past two years as more and more new materials and technology have entered the market in an effort to tackle the issue.

For our first feature, we talked with Reebok's Senior Product Manager, Keith Stern, to learn more about how Reebok's sustainability efforts, particularly their Ree[GROW] and Ree[CYCLED] programs along with a discussion on one of the best performing sustainable shoes in the market - the Floatride Energy Grow.

Bach: Thanks so much for speaking with us about Reebok's efforts regarding sustainability. Can you tell us a bit about yourself and how long have you been with Reebok?

Keith Stern: Thanks for having me! I am the senior product manager for performance running footwear Basically anything that is Floatride Energy is what I manage. I've been doing this for three years now, but I've been with Reebok for 12 years. I have a background in engineering and biomechanics. I came here and started in on research and development with our innovation teams and then transitioned about two years ago into product management.

Awesome. Can you talk a bit about how long has Reebok been considering going green and focusing on sustainability? Has this been talked about internally for a long time?

Yeah, definitely. It actually started with the innovation teams that we work with. We have a team that works on projects that are 3-5 years down the road, and they really start with how things are made. They aren't creating a final product, they are more looking at how we build things, the manufacturing process we use and innovations. Even things like developing the Floatride foam we put into our product. That came out of the innovation team trying to do foam development.

In 2013/2014 we worked towards building out to a material library that would be more sustainable. The first easy piece was just swapping any virgin polyester over to recycled polyester. That's part of the brand's larger initiative just to eliminate virgin polyester from the supply chain because suppliers are used to swapping out that source material. It's more of a one-to-one approach. The harder piece is moving over to our bio plastics. Plant-based ingredients that can make that type of material. The first type of iteration we initially launched as a cotton and corn product, which was a lifestyle shoe so kind of in the name it was name of cotton and corn ingredients. The upper was a relatively simple cotton execution and the bottom was made with a corn-based bio plastic. I think that shoe was really interesting because it was the first time we were able to release a plant-based product, and it was actually I believe over 75% plant-based ingredients by weight.

So that's something we kept core to our Ree[GROW] initiative, making sure we work with the USDA bio-preferred to externally validate that our product is actually plant-based, but that we have that third party validation. The downside of the product though was the comfort of the foam. The way it was constructed was actually called a cupsole where a corn-based material formed the midsole, but not really the cushioning. So it formed a structure, but then we used a thick sock-liner insert as the cushioning structure. Obviously the performance wasn't really there. It's a lot stiffer. The thing we had to crack was the foam. We didn't really have a high performance foam that was plant-based. There was some stuff in the market already. All-Birds uses their sweet foam which they have open-source right which is sugar cane EVA. That material wasn't performance as our running product, right? Ever since we used Floatride Energy and Floatride+, using these foams that are better performance than EVA. We have to be able to find something that was plant-based ingredients, but also just as good as those foams.

Kind of like what you talked about where consumers are interested in sustainability, but only if everything is equal - if it costs the same, performs the same - because when you are buying a running shoe, you are buying a piece of equipment right. It's as important how it performs. So that was our goal. We set out to see how we can make a product that performs just as good as our non plant-based product. The solve was really the plant-based foam, like I said, and the reason I think it is as good as it is because we use the same exact manufacturing process as we do for our non plant-based performance foam. So our Floatride Energy foam and Floatride Energy Grow foam is made in the same way. Made in the same facility with the same pressurized nitrogen tanks and everything, so it has a very similar look and feel and performance to it.

Photo provided by Reebok.

I actually want to talk about that, because I spent a lot of time in both shoes - I'm not sure how, but I don't review many shoes as the team's social media manager, but I somehow ended up reviewing all of Reebok's products in the past two years. Coincidence? Maybe.

The one thing I was fascinated by is that they are very similar in hand [the Floatride Energy 3 and Floatride Energy Grow]. You did a fantastic job of mimicking the same experience in these. There are obviously some ride differences in the shoes and some things you are working on, but when I'm holding this and looking at it, it was really interesting to see how similar they are. You aren't picking up a different shoe at all, you really just have another running shoe at the end of the day. I was interested in when you were redesigning the Floatride Energy 3 in particular, was it redesigned with the intention of this - the Energy Grow - as well? The similarities in hand are impressive.

I don't think we changed the design of the base model to make it easier to make it a plant-based product. But the intention was whatever we make as a plant-based should be exactly the same as the non-plant based. We used the same exact geometry for the midsole, like I said made at the same supplier. A lot of the characteristics is made up from the foam and how it performs, but geometry matters too. We had a shape that works for us; why reinvent it? We talk a lot about this for the industry for example. I think there is different opinions, but why does the Cyber Truck look like the Cyber Truck? Why can't it just be like what Ford does with the F-150 Lightning. It's the same exact look, but made with an electric engine. We wanted to do the same thing here. We're not making the weird granola stuff that looks different because it's sustainable. It should look like a normal running shoe, and oh by the way it's a sustainable product.


Polyester is one of the most commonly used materials in clothing. It is made from a chemical reaction between air, water, and petroleum. It was born out of material research in the 1920s by Du Pont. Commonly used polyester is known as "virgin" polyester because it is created by a nonrenewable resource - petroleum. Recycled polyester offers an alternative by using plastic waste that already exists. It takes far less energy to produce and produces far less emissions. The quality of the material remains pretty much exactly the same.

Recycled polyester is an important step forward to immediately cutting emissions from virgin polyester. However, long term it is only a stepping stone in that recycled polyester is hard to reuse once used. It is often blended with other materials, making it almost impossible to recycle and reuse. It can also be hard to color, which is why cleaner colors like a pale white or yellow is often very common.

The negatives aside, recycled polyester is still an easy way for companies to swap out usage of virgin polyesters as sustainable material science continues to advance and improve.

Learn more: Eco-Sustainability of the Textile Production: Waste Recovery and Current Recycling in the Composites World

I think that's very interesting, the fact you are able to get the same performance in a lot of ways with subtle differences in the materials. You mentioned price point. I think that's the big thing about the Floatride Energy Grow that doesn't get enough credit. We talked a little bit about in the review, but in hindsight thinking about it building up to our interview I really wish I talked about this shoe more. I think you have done a lot with this shoe for the price point it came out at. A lot of companies have gone sustainable, but with subtle changes to the upper for instance. There's not too much being done below. Here though, you are doing a lot with this one shoe which I thought was really interesting.

A big part of our brand philosophy, specifically in running, is to be more accessible. So we very deliberately try and make product at a value-driven price point. So we wanted to make sure we still held that for our sustainable products. Truthfully, it is $20 dollars more right - $100 vs. $120. It's not that we think we can get more value because it is sustainable, it's just the materials we use are more expensive. I think long term that is going to adjust. As more suppliers invest in plant-based ingredients whether it be bioplastics or performance, I think those prices are going to go down. Especially as brands move towards those ingredients. It's happened with recycled polyester. They are very close in terms of pricing. I think in the long run we'll get there. We try to kind of meet consumers halfway. We're subsidizing it a bit. It's not the same margin as our other product, but we did that intentionally because in the long run we want to get to a point where there is no price premium at all. We can swap all of our product to a plant-based product at the same price and same performance.

Can you talk a little bit about the Floatride Energy Grow midsole? This is a castor bean midsole correct?

Yes, the midsole is castor bean oil. The midsole is about 55% plant-based by weight. We do that through external testing. They essential do carbon dating: they take a small amount of material, incinerate it, and then you can date the carbon that comes out of it. And anything that is older than a certain point is petroleum based and anything new is plant based. So more than that is plant based. The plant based ingredient is castor bean oil. It has good properties in substituting for petroleum based oils in this case.

What is interesting is that the base of the Floatride Energy material, the non plant-based, is a TPE base. When we go over to the caster bean oil it actually is a PEBA based; it is more similar to the format we have in the Floatride+ foam. That PEBA based material is actually slightly lighter material than our TPE material. So there is some performance benefit swapping over to the plant-based alternative. A little bit lighter weight, and the same cushioning and energy return to it. Overall a really good foam and like I said, it processes in the same way at the facility so we're able to get the same net performance.

It took awhile, right? Some of them were higher bio content. Some of the mixes we tried, but they didn't perform as well. So again, hopefully over time we can increase that more and more as we go forward but it was really important to us that we could have something that was just as good performance wise. So bringing that down a little bit from 75% plant-based to 50% plant-based, we felt like that was still a step forward and plant based,=. Over time we'll continue to put more and more plant-based ingredients.

Editors Note: Learn more about castor bean oil for midsoles and more in the Culture Corner of our Floatride Energy Grow review. Click here to read.

The other components are unique too, because there is a plant-based component through every part of the shoe right?

Yeah, it was going through the build materials and trying to swap out the best we could, one-for-one into a plant-based ingredient. Even the heel counter right, which is usually a plastic component, we swapped that over to a plant-based plastic instead.

Ree[GROW] focuses on creating products with natural materials.
Ree[CYCLED] focuses on creating with recycled or repurposed materials

How do you feel about the shoe now? What are your general impressions now that it has been a little later?

Yeah, I really like it, I'm wearing it right now [laughs]. I'm really excited about it. I think it was a good step forward in terms of being able to deliver a performance product that is plant based. We always try to be as critical as possible, especially when we're working on the next version. I think we made some good improvements from the very first iteration of it to the one that's out now, just switching to that midsole and then removing some of the stretch and excess movement in the upper.

I think we can probably do that a bit more right? When we have this plant-based upper. That's the biggest difference. The outsole and midsole are pretty much one-to-one. Some of the upper materials that are plant-based are not plant-based plastics; they are just plant-based materials. They are not quite as 1-to-1 on performance between the two. When you held up the Floatride Energy 4, that's also sustainable in terms of the upper being recyclable polyester. All of the main materials don't have any virgin polyester in there. The majority of our performance line has moved over to recycled, so everything in our performance running range that's out now qualifies as our Ree[CYCLED] capsule or our Ree[GROW] capsule.

About this Speed Shift upper, in our recent review I talked about how it's pretty cool that you are able to integrate the sustainable materials into this because I do think it is breaking the gap a bit as a halfway point as far as price. This [Floatride Energy Grow] being $120, this [Floatride Energy 3] being $100 and this [Floatride Energy 4] being right in between. I think there's more than fair excuse right now of course for it to be $110 even with the cost of the material with the rising cost of everything I think people would probably still have been okay, but it's admirable to see the sustainable upper come in and not dramatically tick up pricing.

Our goal with that one [Floatride Energy 4] to primarily to reduce weight. Because we already had a lightweight product in Floatride Energy, we wanted to see if we could sneak out an extra half ounce in the product. The goal was to deliver something that was lighter weight, but still has the same amount of structure to it. That was really the only goal, it wasn't necessarily to make it sustainable.

However, because we were moving our range over to be sustainable, that was the extra requirement right? You can only use materials that are 100% recycled polyester. Like I said on the recycled front, they are moving a bit faster. Suppliers have spent more time investing into recycling plastic alternatives. So there is a little more in terms of what is available. What we typically do when we start a project now is when our design and development team select a material based on performance, if it's not currently a recycled polyester, we work the supplier to get a recycled version. Typically they are willing to work with us on that. We haven't had a lot of issues with having a different price or performance with it so I think the more that companies are willing to push to get things pushed to sustainable materials, we'll get there faster. There is a small price difference, so you have to be willing to design around that, but we've been really successful in moving over to recycled polyester rather instead of virgin plastics.

I think y'all have done a great job because you have a great base product. This is a proven go-to and people love it. This is one of the five shoes people talk to us about all the time and get really excited about whenever we discuss it.
Is there going to be another variation of the Grow for the 4?

Yes, what we did. The next thing we ran into an issue with is pricing right. So, performance shouldn't be sacrificed and price shouldn't be sacrificed either. So we're trying a little bit of a test and learn approach. We're releasing a product called Floatride Century Grow and it's actually built on the previous midsole geometry for the Floatride Energy and it's a little more bridging that gap between performance and lifestyle. So it's definitely still runnable, it's on the same platform as before, and now the upper is a little more deconstructed. We found through consumer feedback that the people who were buying the Floatride Energy Grow, more of them were buying it to wear as an everyday silhouette rather than dedicated running shoe. We wanted to try to take that as feedback and work with that. So the new product will be the same $110 price point as our non plant-based, but look and feel different because the previous midsole geometry we'll put it on.

"...I think you are absolutely right. Performance is the number one requirement for a running product. Because there is not a lot of it out there, there is some skepticism that when it's plant-based is it going to perform. Is it going to fall apart faster? That's the big thing: is it durable enough? That's a big question people have."

I can certainly understand. We joke about lifestyle a little bit on the team, but this shoe - the Floatride Energy Grow - was one of our top favorite everyday models of last year just based on looks alone. I can see why it was very popular in that respect.

That's great. I think long term, even if stuff isn't in our Ree[GROW] capsule, I think there are components that are easier to swap one-for-one. So for example, moving to natural rubber in all of our stuff, or moving to a sugar cane EVA sockliner. Gradually introducing more and more plant based as well as recycled material into our base product is something we are looking to do as well. We'll have those pinnacle products that are Ree[GROW] where we are pushing the limits of plant-based ingredients that we can put into a product that can perform and look good.

Ultimately one of the things we're trying to solve is the end-of-lifecycle for products. Right now we're focused more on what goes into the product, but ultimately - running footwear especially - is the utility product. It has a lifespan as people wear through it. What do you do with it when you are "done?" Right now the burden is on the consumer to figure that out. I think some other brands are trying some interesting approaches in terms of like a subscription base where you return the product and they send you a new one kind of thing. I think the goal long term is something compostable or biodegradable so that it is easy to put it in your compost and get rid of it that way and feel better about what's happening with product. We're not there yet, but ultimately that's the long term plan.

That makes sense. Sustainable, reusable clothing tends to be a lot easier, because you can patch and restore clothing for a very long time. There is certainly an end life with most footwear though.

I do want to talk about challenges. There are huge investments to go this route. Can you highlight some of the production challenges in going green at Reebok?

Yeah I mean, first and foremost is being willing to go and find new suppliers who will try new things with you. Getting to the point of this performance foam, it took a long time. It took a couple years of development to get to that point to swap it out and have it perform one-to-one. There's a big time investment and financial investment to get there. Early on in the process we were exploring different types of materials to use and there's actually a mushroom based plant we were working on. Mycelium is a really interesting plant-based ingredient right? They are using it in packaging. It's a leather substitute. It's showing in a lot of places. We tried to use it as a foam. I'm not sure if you are familiar with the foaming process, but in a typical injection molded foaming process it's a molten liquid that gets put into a mold and then there's a chemical reaction that happens that when you open the mold and it's exposed to air, it'll expand rapidly. What you need is stuff that wants to expand and then other stuff that wants to hold it together - and there wasn't enough stuff to hold it together. When the mold opened, it just shot out everywhere, just globs of this mushroom based foam all over the place. That's why it is helpful to find suppliers that are willing to experiment and work with you and try a lot of different things at once. We had the corn going and the castor bean and kind of competing to see which would perform the best and work out long term for us.

Did you have to make big changes internally just to make it possible to use these ingredients or is just shifting...

Yes, we have a sustainability work stream. One of the biggest things is the certification process. We're very aware that green washing is a big issue and we don't want to contribute to that. We want to make sure what we are doing is ethical and sustainable and that we are approaching it in the right way. I think having that certification process in place to make sure we are doing things in the right way is really important. And then getting our development team and materials team onboard as well to change the way we do things especially for those basic things like the heel counter. We're very used to spec'ing out the materials and it's the same heel counter materials every time. Just to make that switch while you are building this, you have to look at every single component. It's a mind shift for every member of the team to be willing to dedicate the time and energy to solving all the problems.

Even from just a farmer point, a farmer have to jump through a lot of hoops for sustainabiliy.

It's tough because sustainability is not well-defined. I'd love to see more of that across the industry too, of just level setting. Some retailers are doing a good job of it also, because when you go to a Dick's Sporting Goods for example, you can sort by sustainable products. Then what does that mean, when a product shows up? Being as transparent as possible is where we need to be and why we've gone the route to using the USDA bio-preferred program to help validate and certify our plant-based ingredients.

Two last things I wanted to touch on, first from the consumer side. Can you talk about the challenge of talking about a shoe like this to the running population? I know as much as we do and as much as we are excited about sustainability, at the end of the day people just want a good performance shoe which you do very well.

I think you are absolutely right. Performance is the number one requirement for a running product. Because there is not a lot of it out there, there is some skepticism that when it's plant-based is it going to perform. Is it going to fall apart faster? That's the big thing: is it durable enough? That's a big question people have. Being able to prove that is part of our goal. Can you run a marathon in it? How many miles will it hold up? We made sure we tested it the same way we test all of our products. It's just going to take time I think for people to shift their mindset of what they are looking for. I think in general there are so many things we can do as consumers to shift our behavior to be more sustainable and this is just one of them. At an individual level, it's relatively small. Within the industry is relatively big. It's definitely more on the industry to make changes and hope consumers will follow. We have to meet consumers halfway though, because it's not useful to make products that consumers aren't interested in buying. We need to make sure we are solving for that also. When we talk to people, people will find a different behavior to offset. Like going to a plant-based diet. I've done that personally. It's probably the biggest individual impact you can have on the environment right, to go to a plant-based diet. Just based on greenhouse gas emissions, water use to breed livestock, etc. Some people may do that and say, well because I'm doing that it's okay that I use a gasoline car and take these flights which balance your carbon footprint out. Where does clothing and footwear really fit into that equation? Everyone has to make those individual choices, but as more and more products throughout the industry shifts into this sustainable lens it'll be second nature right? That's how product is made ultimately.

Kind of thinking forward - 3-5 years - how far is Reebok from being fully sustainable?

Across the brand, Reebok has a goal is by 2030 to have all of our products to be Ree[CYCLED] or Ree[GROW]. I think it's very attainable that we'll eliminate virgin polyester fully from our lines in the next two or three years by using a mix of recycled and plant-based ingredients. I think it'll take longer for higher bio-preferred content in our products overall and then I think the compostability/biodegradable is definitely more like 5-10 years. That's going to take a while for us to make a product that's going to perform when you are using it but also still have a safe end-of-life process.

Maybe you need 5% mushroom compost to speed it along [laughs]

More mushrooms in there for sure! [laughs] The other challenge is working with suppliers, but also working with compost facilities at end of life. There have been some challenges: how do they know as they are sorting through compost that it is a compostable shoe vs. any other shoe that is not compostable? So if they make a mistake, it's going to contaminate all of their compost. It may need to be a thing when it is first started that it's a separate facility and I think that's why brands are approaching as a send-back as a solution. But that still puts a lot of burden on the consumer of what to do with their product at the end of life.

Because of COVID, has going bio-based helped or made harder anything?

I don't think there's a difference in terms of the supply chain. I think it's been affected equally. A big part is labor force. Everyone has been affected by it and for suppliers who have to stay home, no one is building product. It's about equal across the board.


Special thank you to Keith for taking the time to speak with us about Reebok's efforts! We hope you enjoyed our first feature of this series. We have some exciting interviews coming up with both brand innovators, researchers, and more. Stay tuned! In the meantime, make sure you stay tuned to DOR for the latest shoe reviews and conversations on running footwear.

If you would like to talk with the team about the Sustainability Project, email Bach Pham at

Further Reading
New Balance Fresh Foam X More Trail v2 - A very high stack trail runner for long distances
New Balance Fresh Foam X 880v12 - A well-fitting workhorse for your daily training needs
Puma Fast-R Nitro Elite - Puma's new super shoe packed with interesting technology
Skechers Razor Excess 2 - A higher stacked shoe that now features a forefoot plate
On Cloudmonster
- On Running's new maxium cushioned shoe!

This discussion was not a sponsored piece with Reebok. We appreciate Reebok for their time and willingness to talk about product and challenges with us.

Next: Puma Fast-R Nitro Elite Review

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