Why they're Awesome
SPEED: Insanely light 1-ply upper, strategically placed rubber, speed platform, rocker design
EFFICIENCY: A pace-tuned midsole with a forefoot FastPod delivers optimized cushioning and maximized propulsion efficiency for the pace you run
COMFORT: Wide toe box, contoured heel pocket, lively pace-tuned feel
Z20 Design Notes
ENGINEERING SPECS: Average adult ranges for height, cadence, and body weight at this pace.
CUSHIONING: At this pace, when your stride's flight distance is the greatest, you generate a lot of force on impact, so we’ve tuned the reaction density of the heel and midfoot to provide optimized cushioning for the forces you create. Forget about "max" cushioning for some rando runner—the Z20 gives you the best cushioning for the way you're running today. We call this pace-tuned cushioning. The only way to get the best cushioning in a running shoe is to tune it by pace.
PROPULSION: At this pace it takes a lot of force to push off hard enough, so the last thing you want is a squishy, inefficient midsole. We’ve tuned the forefoot FastPods in the Z20 to deliver maximally efficient energy return given the forces at this pace.
DROP INFO: Runners at this pace are usually lightweight and often midfoot or forefoot strikers. With this in mind, we built a 4mm drop into the Z20. This helps prevent a negative heel drop angle upon impact.
SOLE DESIGN: Rocker design and fortified arch outsole for ideal propulsion. According to a recent paper on arch compression, forces on the arch are greatest during the push-off phase of your stride (not the impact phase). Most shoe designs carve out the arch area, exaggerating pronation. The Z20 fills the arch area to provide support during push-off, precisely when you need it most.
MIDSOLE MATERIAL: Vimazi Z-Foam has an EVA (ethylene vinyl acetate) base. Proprietary additives have been mixed into the EVA to increase abrasion resistance and elongation properties. Most importantly, however, we use our specific EVA blend because it allows us to dial in an ideal compression set for each model. This isn’t possible using other common midsole foams. Finding a foam matrix that could be specced to specific durometers was one of the reasons it took five years to develop and produce our pace-tuned shoes. Our midsole formulas are the heart of the technology. They’re what allow us to tune the Vimazi Z20 to a peak force spec of 850N in heel/midfoot and 1200N in forefoot (W11.5). No one else does this, and you can't tune shoes in this way using other midsole foams.
Why you need a pace-tuned shoe
Everyone running in the 5 minute mile range wants excellent cushioning with the most dynamic push-off possible. While running, we generate a wide range of both impact forces and propulsion forces. Those forces are intense at 5 minutes per mile, but less so at 8 or 10 minutes per mile.
At Vimazi, we carefully studied midsole materials in light of the forces running creates, and we found that it’s physically impossible for one midsole to respond efficiently and appropriately to all paces. For better performance, this means midsole densities should be adjusted to the speed of the runner.
Our research also showed that the propulsion forces in your forefoot and toe are greater than the impact force you encounter in the midfoot and/or heel. As a consequence, running shoes need to be tuned both by pace as well as between heel and forefoot, at least if you want a better running experience.
By adjusting midsole density in the heel and midfoot to the forces you generate at 5 minutes per mile, we’re able to give you the precise amount of cushioning you need at that pace, no more and no less. This pace-tuned cushioning ensures stability, comfort, and health benefits over a lot of blazing fast miles.
But you don’t want better cushioning to infringe on the most lively energetic push-off possible. To get the lively push-off you want, the forefoot has to be tuned differently than the midfoot. That’s why the forefoot FastPod in the Z20 is specifically engineered to respond to the propulsion force at 5 minutes per mile.
This is how the Z20 reduces shock while increasing energy and efficiency when running between 4:30-5:30 minutes per mile (2:50-3:20 minutes per kilometer).