So how do these shoes work their magic? Let’s break the three components: cushioning, the carbon plate, and shoe shape.
What Cushioning Really Does – Explained with juice boxes
Imagine you’re jumping up and down on a juice box. Every time you land, the box squishes, then pushes back up a little. If the box is too soft, you sink and waste energy. If it’s too hard, your legs take all the impact.
Now imagine a perfect juice box— it squishes just enough to protect you, but then springs back fast to help you bounce forward. That’s what good foam cushioning does.
In Saucony Endorphins, this magic material is called PEBA (polyether block amide) foam. It’s super lightweight and extra springy—like a supercharged trampoline under your feet. But how does PEBA foam do all this?
(PEBA polymer formula)
Recall the perfect juice box is the perfect combination of soft and hard. Well, in PEBA, the PE (polyether) is the soft component, and the PA (polyamide) is the hard component. Because they alternate with each other in the polymer, PEBA is half soft and half hard. That gives it the flexibility of soft materials without collapsing under your legs.
Interestingly, there is an entire class of these types of materials called thermoplastic elastomers which are polymers created with half rubber and half plastic monomers like the PE and PA components of PEBA foam.
The Carbon Plate – Explained with diving boards
While PEBA foam would make a great shoe alone, it still lacks some stability, so we need to make a more rigid shoe. Now imagine running on a diving board. When you push down on the board, it bends, stores your energy, and then releases it to launch you forward. That’s exactly what the carbon-fiber plate inside Endorphin models does. Carbon-fiber also happens to be extremely light for the support it provides, making it optimal for lightweight running.
How does carbon-fiber work? Well, it’s made of thousands of “carbon-fiber filaments” 20 times thinner than a human hair. Each filament is made of 5-10 µm thin crystalline carbon nanostructures that can be thought of as crystalline carbon spider silk. These individual filaments are then intertwined like rope under high heat to create intra-filament bonds. That’s the reason carbon-fiber is so strong– while its inter-filament bonds are some of the strongest bonds in nature, the sheer number and strength of the bonds between the filaments make carbon-fiber one of the toughest materials out there.
The Speedroll Geometry
Saucony adds something called Speedroll Geometry, which is just a fancy way of saying the shoe curves like a rocking chair. This shape:
- Helps your foot roll forward more easily
- Reduces the work your legs have to do
- Makes running feel smoother and less clunky
