Imagine, for a moment, that you’re nearly a half-mile above the rest of the world, tiptoeing across conglomeratic sandstone vaulted atop Precambrian granite. This rock is hoisted more than 7,000 feet above sea level, thanks to the robust — and erratic — tectonic collisions of 65 million years ago. Overlooking the charming city of Boulder, Colorado, from the top of the region’s celebrated Flatirons, you have more than a thousand feet of air to your left, and hundreds more to your right. The only thing keeping you stuck to the terra firma beneath your feet is willpower, your physical faculties, and two smears of rubber called soles.
Fortunately, scientists (and a handful of very studious designers) have spent years developing, prototyping, and testing materials—and stitching them all together—so that folks like you (and superathletes like that guy from Free Solo) can pull on a pair of shoes and surefootedly explore the world, high and low. One of the labs at the forefront of this highly-specific science is the Merrell Test Lab, an innovation incubator established in partnership with Merrell’s roster of elite athletes (like Ragna Debats, a renowned ultrarunner who has a cache of trail ultra race wins under her belt).
Merrell Test Lab (or, MTL), was launched in 2019, with the purpose of conceptualizing and designing footwear that was capable of performing in tricky, wild, rocky, wet, steep, and otherwise technical terrain and—perhaps more importantly—allowing the wearer (whether they are a professional athlete or literally anyone else) to move securely and safely, have a good time doing it, and stay reasonably comfortable given the conditions.
The two newest products to come out of the Lab, the MTL MQM and the MTL Long Sky 2, were engineered over the course of several years with the help of elite trail runners and mountain pros to challenge what’s possible — and to allow athletes to think less (read: worry less) about their feet and enjoy more of their time outside. The result is two designs that cleverly apply material sets and unique construction. Think laminated mesh, moldable rubber compounds, and ESS rock plates.
THE ORIGIN OF FOOTWEAR
While shoes may not seem like the most technological apparel to figure out (biological changes in foot shape and toe strength indicate that people were using footwear with substantial soles about 40,000 years ago), it turns out that there is a science to not only protecting our feet, but also allowing us to push our abilities and travel places and distances we otherwise could not. Innovation in materials, understanding of anatomy, and advancement of technology have brought us a long way from wrapping our feet in hides to inventing and applying rubber that’s been re-shaped at high temperatures under our soles so we can traverse terrain high and low, no matter the conditions (which is one of the strengths of the Long Sky 2 and MTL MQM designs).
The human foot contains 26 bones (a whopping 25 percent of our entire skeletal count), 33 joints, and over 100 tendons, muscles, and ligaments. That’s a lot of infrastructure, because our feet have big jobs. Early hominin (our very ancient ancestors) evolved to become bipedal around six million years ago. Their pelvises became more closed to accommodate the musculature needed to stand upright, their knees widened to adjust for increased pressure and stress, and their feet became something of a technological advancement themselves. Research published in 2019 found that our ancestors’ feet developed to lose an opposable digit in favor of a longitudinal arch (LA) and plantar intrinsic muscles (PIMs) that stiffen the foot. Toes shortened and straightened out. The ankle became finer—all to aid in adopting a bipedal gait and supporting the body's full weight. These new feet allowed the earliest hominin to leave the trees and set forth into savannahs, mountain ranges, and terrain never explored by humans before.
GO FAR
Our feet have evolved to take us far and wide. But your average foot these days still isn’t equipped to withstand rocky crags, snow fields, stream crossings, or even an asphalt bike path on a hot summer day. Pushing the boundaries of innovative materials and construction in footwear has not only allowed us to travel in these types of conditions, but to do it efficiently. And comfortably.
When Ian Cobb, Senior Design Director at Merrell, first began to concept the Long Sky 2—MTL’s newest trail running shoe—with his teammates, he knew what they needed to develop footwear tech that not only has the ability to provide protection from the elements, but also withstand myriad conditions and allow the wearer to perform at their personal best. Oh, and take into account that trail runners and hikers live in diverse landscapes with varying terrain, have individual goals for training and objectives, and have foot compositions that vary from person to person. It was a tall order to fill.
“That’s the gift and curse of MTL,” he says. “Because we are collaborating with athletes and testers we are constantly combining what others are experiencing with our personal experiences and testing and putting it together.”
In the case of the Long Sky 2, that led to the team building seven prototypes that went through 2,500 hours of testing—in the field, in the MTL lab, and in third-party labs—before the team felt like they landed on a fit and material set that pushed the boundaries and performed well.
The final products are two shoe designs that complement our modern-day bipedal needs by not only protecting our feet, but also aiding in increased capabilities and performance.
The Long Sky 2, a trail running shoe, allows ankles to be in a more natural position in stride, made possible by a pared-down 4mm heel drop. In order for wearers to have a better return on their stride and increase step cadence, the shoe is 10 percent lighter (weighing just 1 lb. 3 oz. for a pair of men’s size 10.5), and has a bouncier, less-dense foam that uses less material overall (hooray for reduction!). In order to preserve comfort (and intact skin) over the course of many miles and many hours, the Long Sky 2 was designed to have a 30 percent lower water retention than its predecessor. To achieve this, the upper of the shoe is constructed of knit mesh laminated with TPU (thermoplastic polyurethane) to deflect water in key areas that are the most likely to get splashed. But in the rare case that this hydrophobic composition gets submerged (and, duly, becomes wet), the shoe’s TPU overlay was designed to retain less water so it can dry quickly, too.
In fact, this shoe spent days inside buckets of water and hung up on coat hooks to test just how quickly it could dry. “We know that many wearers need their shoes dry the next day if they get them wet on a run,” Cobb explains. “So we really analyzed every material to see how much water each picks up and to only use what we needed. That resulted in a shoe that dries faster than all of the previous shoes that we built and even competition.” To finish with a nerdy cherry on top, MTL researched which position shoes dry fastest in, and found that it’s hanging by a hook. So, put on a pair of Long Sky 2’s today, and you’ll find a loop on the heel, placed there so you can easily hang your shoes up when you get home.
GO ANYWHERE
That same level of research, design, and rigorous testing (2,500 hours and the feedback of many professional athletes) was utilized in the creation of the MTL MQM—which stands for “Move Quicky over Mountains.” As the name suggests, the design was specifically created for objectives in rocky, steep terrain that toe the line between a hike, a run, and a rock climb (an endeavor called “scrambling” by some). From an evolutionary standpoint, mountain goats and ibex are better adapted for this than we. But now we have a shoe for that.
The MTL MQM is informed by both trail running shoes and technical climbing shoes, creating a hybrid that can nimbly scale rock faces to the top of a ridge or peak and still support the wearer on the downhill run. This type of specific endeavor usually involves over a thousand feet of climbing and relatively low mileage. “It's been engineered to be able to edge and scramble really well without sacrificing trail run capabilities,” says Cobb.
To accommodate this, MTL designers used a combination of moldable rubbers and lug specifications on the sole of the shoe. The toe and toecap are soled using a lug pattern similar to that of a proper climbing approach shoe, constructed out of Vibram IDROGRIP rubber—which is capable of gripping to rock routes that are rated as 4° by the UIAA, the International Climbing and Mountaineering Federation. Grade 4° applies to routes where “holds and supports become more rare and/or small. It requires good climbing technique applied to various rock structures (chimneys, crevices, etc.), as well as a certain degree of specific training." Serious stuff.
The heel of the MTL MQM is composed of the less aggressive—but still very grippy—Vibram MEGAGRIP, a rubber compound often used on technical trail runners. The challenge of molding two rubber compounds together without melting one into the other, while leveling a plane where the lugs in the heel could be longer than the lugs on the toe and midfoot to allow more surface contact on the climb and more stability on the downhill, was a demanding task for the team to take on. But after plenty of tweaks, they got it.
To finish the MTL MQM’s design, the Lab incorporated a rigid ESS rock plate that connects to an extended ESS wrap that extends up to the midsole, protecting feet like the footwear version of a roll cage while simultaneously allowing for more traction on climbing moves when the edge of the shoe is needed. The team took out the heel cup to protect the Achilles tendon from being injured on steep uphills, and used a TPU lamination over the mesh upper (similar to the Long Sky 2) that is strategically placed to protect your feet while still allowing them to properly temperature regulate (the laminate isn’t applied to the top of the shoe, where the foot releases the most heat and where contact with rocks is minimal).
Combined, 5,000 hours of testing and years of research went into the creation of Merrell’s latest two designs from MTL, made for people who like to spend time outside. That level of analysis is the human-made, modern-day version of our ability to continue going places further and faster than we have before. So the next time you pull on a new pair of shoes, thank the hominins. And the R&D team.
This story was produced by WIRED Brand Lab for Merrell.
