Saucony has long been a name synonymous with premium running technology, yet its journey through the decades of midsole innovation reveals a brand that never rested on its laurels. While many sneaker enthusiasts associate Saucony with classic silhouettes like the Jazz Original or the Shadow series, the true backbone of the brand’s legacy lies in its relentless pursuit of a better ride. From the early days of simple EVA foam to the modern marvels of supercritical fluid processing, Saucony’s midsole story is a microcosm of the entire running shoe industry’s evolution.

In the 1970s and early 1980s, Saucony entered the running shoe market with designs that relied on basic ethyl vinyl acetate, a lightweight and moderately cushioned foam that was a step forward from the hard rubber soles of the previous generation. The original Saucony Jazz, released in 1981, featured a standard EVA midsole that offered decent shock absorption but lacked the durability and energy return that later technologies would provide. However, even then, Saucony distinguished itself by paying close attention to fit and heel stability, employing a triangular outsole pattern that improved traction without sacrificing flexibility. The simplicity of that early EVA allowed the brand to focus on biomechanical fundamentals, setting the stage for more sophisticated formulations.

The 1990s brought a major shift with the introduction of the GRID system, Saucony’s proprietary cushioning technology that combined a plastic web mesh with EVA to provide both impact absorption and stability. The GRID (Ground Reaction Inertia Device) was a hollowed-out heel insert that used a series of elastic strands to decelerate the foot and then rebound into the next stride. This was not a midsole foam per se, but a mechanical system embedded within the midsole that revolutionized how runners perceived cushioning. The classic Saucony Shadow series, particularly the Shadow 5000 and Shadow 6000, employed this GRID technology and became icons not only for performance but also for style, as the visible grid window became a design hallmark. Yet the midsole itself remained largely EVA-based, with the GRID unit doing the heavy lifting.

As the new millennium arrived, Saucony began experimenting with more advanced foam compounds. The company introduced SSL (Super Smooth Lite) EVA, which reduced weight while maintaining impact protection. But the real game-changer came in the early 2010s with the development of PowerGrid, an updated version of the GRID that expanded the web across the entire length of the footbed. PowerGrid integrated the grid structure into a full-length slab of foam, effectively marrying the benefits of a plate system with the plushness of EVA. This was followed by the introduction of EVERUN, a thermoplastic polyurethane (TPU) foam that offered significantly better energy return and durability than traditional EVA. EVERUN was derived from lightweight beads fused under heat and pressure, creating a resilient feel that didn’t pack out after hundreds of miles. The Saucony Kinvara, already beloved for its featherweight profile, received EVERUN inserts in later versions, and the Triumph series became a plush cruiser with EVERUN topsoils.

The most recent chapter in Saucony’s midsole evolution is the PWRRUN family. PWRRUN is a low-density, responsive EVA-based compound that replaced PowerGrid and EVERUN in many models. It struck a balance between softness and snap, appealing to both daily trainers and uptempo runners. But the true peak came with PWRRUN PB, Saucony’s first supercritical foam. By infusing nitrogen or carbon dioxide into the polymer under high pressure and temperature, Saucony created a material that is extraordinarily lightweight, resilient, and bouncy—similar to Pebax-based foams found in competitors’ elite racing shoes. PWRRUN PB debuted in the Endorphin Pro and Endorphin Speed, launching Saucony into the top tier of modern performance footwear. The foam’s ability to compress and spring back with almost no energy loss allowed runners to feel a propulsive sensation that was previously unattainable from Saucony’s lineup.

What makes this trajectory remarkable is how Saucony has managed to honor its heritage while pushing material science forward. The same brand that built its reputation on the humble EVA Jazz now produces supercritical-foam racing flats that are as advanced as any in the world. The midsole has evolved from a simple slab to a complex matrix of engineered polymers, each generation building on the last. Whether it’s the retro feel of a Shadow 6000 or the carbon-plated speed of an Endorphin Elite, every Saucony shoe carries the DNA of this technological lineage. The company’s willingness to adopt new materials without abandoning its commitment to fit and comfort ensures that its midsoles remain relevant for both nostalgic collectors and modern athletes. The EVA of yesterday laid the foundation, the GRID and EVERUN expanded the possibilities, and the PWRRUN PB represents the current frontier—a testament to Saucony’s belief that the ride is everything.