Inside The Development of The Endorphin Pro

By: Saucony | May 4, 2020

Good Content from: Andrea Paulson, Director of Product Engineering

An incredible amount of work goes into the making of technical footwear. It is a truly collaborative and cross-functional process. At its core, the process includes members from each of three functions within the Product Team: Product Line Management (PLM), Product Development and Design. Often referred to as the “Triad,” these individuals take responsibility for each unique project that is started. The triads can be arranged to work on sport-specific projects (running, basketball, cleated…), or by business category (road running, trail running, track & field), or by price point.  Regardless of the alignment, this is the typical cast of characters that control the fate of your favorite pair of sneakers.  PLM’s are the face of the project. They are the conduit between accounts and consumers, and the rest of the product team. Their job is to know the category they represent, inside out and backwards, and to feed their knowledge to the rest of the Product Team. Developers are responsible for the day-to-day management of the project. Calendar dates, pattern work, material testing, build construction, cost negotiations and communication with the factories all fall into Development.  This role is often the least visible or recognized, but its importance is arguably paramount. Design’s role, while seemingly obvious, has much greater depth. Designers work on specific projects, but they also must understand and cultivate the aesthetic and DNA of a Brand. The rendering of shoes requires artistic talent. The designing of shoes requires a keen sense of industry, trend, and engineering, with a crystal ball full of foresight thrown on top.


Two additional departments on the Product Team are Product Engineering and the Human Performance Lab. The Lab and Engineering are category-agnostic functions within the Saucony structure.  We could be working on a new Walking Line outsole design, a new Trail Line midsole compound, a Competition sprint spike plate, or a Marathon Race shoe. Sometimes we are working on a combination of all of the above. Engineering is a catch-all department that works on everything from new foam development, to incorporation of new manufacturing techniques, to management of all molded parts, and most things that fall into what the layperson would consider “advanced concepts.”  The Human Performance Lab has a fairly self-evident moniker.  They are tasked with testing and validating the impact of product on the consumer (in our case, the runner), and vice-versa. It is not to diminish the importance of this particular group with an over simplification of their roles.  Instrumented treadmill data, high-speed video, pressure sensor data, VO2 Max protocols: all managed and filtered by the Lab. This is where you find the PhD’s and nerds. (I can say that because I am one…a nerd, not a PhD.)

While it may be hard to believe, the foam development for the shoe that eventually became the Endorphin Pro started over seven years ago. Polyether Block Amid (PEBA) is a type of thermoplastic elastomer (TPE). The running industry has been using PEBA block copolymers for decades. Saucony, specifically, makes almost all of our sprint spike plates out of Pebax®, which is Arkema’s tradename for a stiff yet flexible, fatigue resistant compound. You probably have 20 PEBA-based products within your reach right now, but have never thought to categorize it as anything other than “plastic”.  Electronic wiring, car parts, sporting goods, medical equipment, and fabric treatments all take advantage of PEBA’s multifaceted capabilities and longevity.  While it is an impressive material, there was nothing new about PEBA … until a few years ago.  EVA (ethylene vinyl acetate) and PU (polyurethane), and more recently TPU (thermoplastic polyurethane) have long been the standard for footwear bottom units.  The footwear industry has been subtlety improving these materials over the course of 40 years.  Add this. Subtract that. Push here. Pull there. Foam everything. In October of 2012, Saucony found foamed PEBA.  And it was amazing!

The performance testing that Saucony uses to measure midsole compounds are fairly intricate and, while not proprietary, they are guarded. The basic gist is this: when impacted, how much of the energy does the material return. Run that data through a series of filters of density (how heavy is it?), durometer (how hard is it?), and compression set (does it stay deformed after repeated impacts?), and you have the key indicators of a material.  PEBA foam was a substantial improvement over everything else we had tested to date. There were, however, a few problems. First, the actual process of foaming the PEBA was different. To “foam” something means to introduce air or gas into it. Typically we do this by adding a chemical agent, or a physical process that helps draw or push air into the material. These techniques still held true for the PEBA foam of 2012, but the process used very large machines that were (and still are) atypical for footwear production. That process created the second problem: Manufacturing. Considering the complications of producing the foam itself, manufacturing midsoles would become even more challenging. The process would have involved an extra step or two to create the nicely shaped and detailed bottom unit part that runners expect their shoes to look like. The foamed PEBA behaved badly once these extra steps were added. We had an amorphous block of foam with great results, or we had a beautiful streamlined sculpture that under-delivered. Lastly, a third problem that no one likes to talk about. This stuff was expensive. It cost five to six times what a performance EVA cost.

We continued troubleshooting to make the new compound work for us, but one variable or another wouldn’t cooperate. By 2014, we decided to back-burner that version of the material in hopes that we could evolve the manufacturing side instead. There is a theory we reference in Innovation called “The Law of Accelerating Returns.” Ray Kurzweil suggests that the rate of change and evolution tends to increase exponentially with time. Our team hypothesized that we could count on the production and manufacturing limitations being resolved with technological and chemical compounding innovations we knew hadn’t been developed yet. Saucony had been working on new materials in the bead-foam category at this point in time and were seeing impressive results in energy efficiency and durability.  Instead of foaming materials into sheets or midsole shapes, the material is extruded into little foamed pellets which can then be molded together. When building midsoles out of mini midsole-like beads, the resulting performance characteristics became greater than the sum of the parts. We wondered if we could do with PEBA what we had done with TPU …

Time is not always your friend in Product. The world outside of the Brand does not cease to move forward while we perfect on an idea. Since we started down the PEBA-path; marathon racing shoes had launched, Peba foams had been launched, and stack-heights had been lifted higher and higher (carbon plates have been in shoes for decades, lest anyone forget that). The idea that these “holy-grail” foams needed plates becomes very obvious while working with them. The Saucony Product Team thought process was quite linear: “This foam is very light and super responsive … we should add more of it!  Its still not that heavy … add more still! Wow, now that’s too soft and squirrelly, we need something to defuse and stabilize …add a plate!  The plate has made things very stiff, it should transition through the toe-off better … add Speedroll geometry!”

Fast-forwarding: Development of the shoe and not simply the foam really took off once we had multiple prototypes.  Our team of elite athletes said, “hold my beer,” and testing was passed off to them. Jared Ward ran New York 2018 and came in sixth-place in a pair. Parker Stinson then shattered the 25K American record in a pair.  We knew we had something special. The Saucony athletes are all spectacular humans so doing iterative prototype work with them was easy and inspiring. The Product Team was able to nip and tuck the fit and feel with the help of every elite that touched the shoe. Once we got it where they liked it, we ran it through more rounds of wear testing with the general public. We wanted the shoe to perform at 4:30 pace as well as at 8:30 pace, but more importantly, we want it be durable for runners that might not have the same smooth and efficient strides as our elite athletes.

The Endorphin Pro launched in February of 2020, but the road to get there was long and uphill. We tried multiple upper designs. We opened eight unique sets of casted metal bottom unit molds. We tested a number of carbon fiber plate layups (the order and direction of carbon weave construction.) We moved the shoe from a 4mm offset to an 8mm offset … for those wondering why: These new materials are incredibly soft and elastic.  When fully loaded in strike, the shoe compresses far more than foams of the past. We refer to this loaded thickness the “effective stack height”.  A 36mm tall shoe made of PEBA foam with a 4mm offset, really feels like a zero-drop shoe. Set the shoe at 8mm, and the runner feels more poised and positioned for speed. In total, we made no less than 30 unique prototypes before we locked-in on a suitable combination. Not included or counted are the daily pattern and material tweaks that occur during normal shoe development. Over 20,000 miles were run on our PWRRUN-PB material before we moved into Production.

On a personal note, in my 16 years with Saucony, this is the most proud I have been of a product we have created. It has been an honor and a privilege to have worked on the Endorphin Pro and Speed. Jared Ward, Parker Stinson, Molly Huddle, Molly Seidel, Brian Shrader, Linsey Corbin, Noah Droddy and Laura Thweatt … I work for them. To earn their trust and confidence is the ultimate and most profound gift. I hope that the future proves that we have built something that the masses will trust and enjoy as well.

Meet The Endorphin Pro Team:

Designer:  Chris Mahoney
Developer: Craig Giansiracusa
PLMs: Ted Fitzpatrick, Chad Holt
Lab: Spencer White, Alec Jessiman, Darby Middlebrook
Engineering: Luca Ciccone


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