Shoe Review: Mizuno Wave Sky Waveknit 4

The Mizuno Wave Sky Waveknit 4 running shoes

The Mizuno Wave Sky Waveknit 4 gives you the softest underfoot feel for easy cruising, comfortable long runs and every distance in between.

Designers made a big update to the previous version of the Wave Sky when they removed Mizuno’s signature Wave Plate technology. The new version is a smaller update from model to model, but it still gets an improved ride thanks to a new foam.

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Mizuno used its two softest foams to achieve the plush underfoot feel, including the all new Mizuno Enerzy foam. The new foam lends another level of softness to the already cushy Wave Sky.

Fleet Feet reviewers tested the new Mizuno Wave Sky Waveknit 4 to see how it fits and how the new foam feels. Here’s what they thought.

Tech specs

Mizuno Wave Sky Waveknit 4


9.4 oz (W), 11.2 oz (M)


10 mm




U4icX, Mizuno Enerzy


Everyday training, long runs


Road, track

Mizuno Wave Sky Waveknit 4 Fit and Materials

A close up of the knit upper on the Mizuno Wave Sky Waveknit 4 running shoes

Mizuno built the Wave Sky Waveknit 4 for cruising in comfort.

The Wave Sky 4 has an accommodating fit that starts with the heel. The heel cup is wide without feeling sloppy. An internal heel counter gives the shoe excellent structure, which adds to the secure fit.

The comfortable fit carries into the rest of the shoe, too. Mizuno designed the shoe to fit a wide range of foot shapes by giving it a roomy midfoot and spacious toe box.

A Fleet Feet reviewer who has a wider forefoot says he loved the Wave Sky’s fit because it didn’t pinch or put his foot to sleep.

“It fits my foot really well,” he says. “It doesn’t feel too tight anywhere, and it doesn’t feel too big or sloppy, either. It’s a really comfortable middle ground.”

Mizuno gave the Wave Sky 4 a Waveknit upper that has also made its way onto other Mizuno running shoes, like the Mizuno Wave Rider 24. The Waveknit feels denser than some engineered mesh uppers, but it gives the shoe good structure while still maintaining a bit of stretch for a comfortable fit.

Another big benefit of the Waveknit is its one-piece construction. Because the upper is knit instead of sewn together, there are no seams, which creates a smooth look and feel.

The tongue adds another level of comfort to the Wave Sky Waveknit 4. Mizuno used a soft and smooth fabric to create the tongue. It doesn’t have a huge amount of padding, but the slim profile molds nicely around the top of your foot for a snug feel.

A vent over the toe box helps release excess heat. Testers say the Wave Sky Waveknit felt slightly warmer than other shoes during some of the hottest days of the year so far, but it isn’t stifling or off-putting.

The Wave Sky 4 also has fewer eyelets for the laces than many popular running shoes. There are essentially four eyelets up each side of the shoe (three of the “eyelets” have two lace holes each) and an empty fifth hole at the top of the shoe that lets you try different lacing techniques. Testers don’t think the number of eyelets on the Wave Sky 4 has a noticeable effect on how the shoe fits or feels.

Mizuno Wave Sky Waveknit 4 Ride and Performance

A pair of the Mizuno Wave Sky Waveknit 4 running shoes

The Mizuno Wave Sky Waveknit 4 is an easy-riding everyday training shoe that delivers a plush underfoot feel for many, many miles.

Mizuno’s Foam Wave creates a soft ride. The Foam Wave, which took over last year for the brand’s ubiquitous plastic Wave Plate, has three different foams: U4icX, XPOP and Mizuno Enerzy.

U4icX is a proven performer. It’s the softer kin of the standard U4ic foam, and Mizuno used the cushioning in many of its previous running shoe models. XPOP made its debut in the Mizuno Wave Sky Waveknit 3. The strip of yellow foam imparts a bounciness to the ride that other foams don’t.

The new foam, though, is called Mizuno Enerzy, and Mizuno says it’s both softer and provides more energy return than its previous foam compositions. Mizuno highlighted the new technology in a wild looking shoe of the same name, and introduced the foam to legacy models—see: Mizuno Wave Rider 24—soon after.

With all that foam, the Wave Sky Waveknit 4 is an especially well-cushioned running shoe. It doesn’t have the big stack height of some puffy maximalist shoes, but it does feel soft beneath your feet.

“The new Wave Sky feels great,” one tester says. “It’s very soft without feeling mushy. There’s still some firmness there to push off from.”

Another reviewer gave the Wave Sky 4 a coveted title: softest Mizuno yet.

"This feels like the softest Mizuno shoe I've worn yet," he says. "It offers premium cushion and doesn't bottom out, providing a smooth and high-cushion transition."

The outsole is coated in durable rubber, which creates good grip on pavement and improves the shoe’s overall durability.

Mizuno also eliminated one of the minor issues that some of its other running shoes have: a channel under the shoe that can sometimes pick up debris. Wave Sky 4 designers created a shallower channel that runs through the middle of the outsole, which doesn’t hang onto rocks, pinecones or the spiky seed pods dropped from sweet gum trees.

Mizuno Wave Sky Waveknit 3 vs. Mizuno Wave Sky Waveknit 4

A side by side comparison of the Mizuno Wave Sky Waveknit 3 and Wave Sky Waveknit 4

Mizuno made a big update to the Wave Sky when it jumped from the Wave Sky 2 to the Wave Sky 3 Waveknit. The change from the third to the fourth wasn’t as drastic, but it does have one main change: Mizuno Enerzy foam.

The Mizuno Wave Sky Waveknit 3 used two foams—UicX and XPOP—to create the cushioned ride. The Wave Sky Waveknit 4 adds Enerzy to the mix for even more cushioning. Designers stuffed the Enerzy foam into the midsole while maintaining the strip of XPOP foam in the middle for a bouncier response.

Mizuno made another small change to the lacing system. Last year’s shoe used small strips of fabric sewn into loops to create eyelets for the laces; this year’s model anchors the laces on the upper itself with more traditional holes punched through the knit.

Otherwise, both models look very similar. Each uses a Waveknit upper for a dynamic fit and comfortable feel, and the Foam Wave looks the same. The outsoles are identical, too.

With the exception of the softer ride, you can expect a very similar fit and feel in the Wave Sky Waveknit 4 as the outgoing Wave Sky Waveknit 3.

Tech comparison

Mizuno Wave Sky Waveknit 3

Mizuno Wave Sky Waveknit 4


9.3 oz (W), 11.3 oz (M)

9.4 oz (W), 11.2 oz (M)


10 mm

10 mm






U4icX, XPOP, Enerzy





The heel of the Mizuno Wave Sky Waveknit 4 running shoes
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The Mizuno Wave Sky Waveknit 4 feels easy on your feet.

Mizuno packed the Wave Sky Waveknit 4 full of its softest foams and topped it with a cozy knit upper for premium comfort. Fleet Feet reviewers love the shoe’s accommodating fit and cushy ride, making it perfect for long distances.

The combination of comfort and cushion make the Mizuno Wave Sky Waveknit 4 ideal for recovery days, long runs or runners training for a marathon.

Still not convinced? Don’t sweat it. Fleet Feet's return policy means you can test drive your shoes and gear without risk. If you’re not happy with the way your gear performs, looks or fits, we’ll take it back within 60 days. Plus, you’ll get free shipping on orders over $99 and free return shipping on all orders. That's our Happy Fit Guarantee.

By Evan Matsumoto. Evan played many sports growing up but didn’t go pro in any of them. Now, he’s the digital copywriter for and editor for the Fleet Feet blog where he writes about different foam densities and engineered mesh uppers.

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