The Mizuno Wave Sky is a solid and durable trainer perfect for those who favor more of a heel strike. Initially rigid, the Wave Sky sweetens up over time and maintains a consistent firm ride with plenty of protection, even for the heaviest of runners. Two areas of concern in the upper are the rather narrow fit through the midfoot and use of heavy overlays.
Out of the box the Mizuno Wave Sky is rigid, making the first few outings a bit rough. Over time, the shoe starts to loosen up and hits a sweet spot. Once on, there was a noticeable hint of softness from the insole and Anatomical Sockliner, which helped soften the ride from the firm midsole. Mizuno used three panels throughout the upper called Dynamotion Fit to help create a sock-like secure fit in the midfoot, however, testers found this to be overkill, saying the overlays felt uncomfortable and heavy. The entry point along the ankle is heavily padded, creating a soft collar.
All of our testers felt the Wave Sky was true to length with extra room in the toe box but ran on the narrow side through the midfoot. Heavy overlays attached to the lacing system extending down towards the bottom of the foot add a snug, secure fit but further give the shoe a narrow fit. A firm heel cup and well-padded ankle collar do an excellent job of comfortably locking down the heel.
Noticeable grooves and geometric design throughout the midsole allow the Wave Sky to adapt and roll seamlessly forward as the foot moves through the gait. The firm, full-length U4icX midsole coupled with Cloudwave — a redesigned elastic, thermal plastic wave running from the heel to the midfoot — gave the shoe a firmer ride that didn’t steal from the runner’s stride. Overall, our testers were pleasantly surprised with how responsive the Wave Sky was given its high weight and thick upper.
It’s best to save the Wave Sky for runs when speed isn’t a priority. Testers did note, if needed they could handle faster running, but its weight and heel dominant profile made sustaining a faster pace was difficult.
A soft insole does soften the ride a tad, but the firm midsole still dominates the ride. Heel strikers will get the most from this shoe due to Mizuno’s Cloudwave, which is a plate of thermal plastic under the arch that extends from the heel through the midfoot. This elastic plastic plate allows the midsole to collapse while absorbing the hard impact from heel strikes without grounding out.