Mizuno Wave Sky 9 Review: The Sky is Falling… Or is it?

Introduction to the Mizuno Wave Sky 9

CHAD: “What if?” has got to be one of the most infuriating questions in the philosophical world. And why is that? We can always sit back and wonder “what if” something did or didn’t happen in life, but until we figure out Doc Brown’s formula for the flux capacitor, throw it in a DeLorean, find 1.21 gigawatts of energy, hit 88 miles per hour, and see some serious shit, we can’t go back and change anything.

This little existentialist anecdote might make more sense as I get into my review of the Mizuno Wave Sky 9. The Wave Sky 9 is Mizuno’s max cushioned trainer, which Mizuno claims will make a runner feel like they’re floating. Featuring 44 mm / 38 mm (6 mm drop) of Enerzy NXT foam, which is a nitrogen-infused EVA, a stretch woven upper with a gusseted tongue, and their X-10 carbon rubber outsole, the Wave Sky 9 is designed to be that soft and smooth premium trainer in your lineup, like the New Balance Fresh Foam 1080 or the Brooks Glycerin.

LINDSAY: You never know what you’re going to get when a box of Mizuno shoes shows up, or at least that’s what I used to think. Back in my earlier Believe in the Run days, I tried a Mizuno shoe that I was not a fan of. Perhaps it was just a naive Lindsay who didn’t know what was good for her. Perhaps it was the shoe. We may never know.

The last two Mizuno shoes I’ve tried, though, the Neo Vista 1 and 2, were a true testament to the brand’s popularity. I’m happy to be here reporting on yet another Mizuno shoe — the aesthetically pleasing, maximum cushioning, long-distance bestie: the Mizuno Wave Sky 9.

CARYN: I’ll start with a completely off-topic, but short, discussion of my prior experience with Mizuno — and it’s all on the volleyball court. I’ve already said that my running history starts squarely in young adulthood. I’m a proud, recovering ball sports athlete who spent years on the volleyball court and lacrosse field with a team, hating anything related to timed running (fellow ball sports athletes, unite). All of my volleyball shoes were Mizuno, and they were fantastic. They were comfortable, supportive, and had the best sole for truly testing the upper limits of your ankle stability.

Despite working in specialty run for several years, I never even tried a Mizuno running shoe on. Nevertheless, I was pretty excited to see a Mizuno box on my doorstep in a totally different context — would my love for Mizuno transcend sports? Time to find out.

WIDE-FOOT JARRETT: You got all the fancy deets about the Wave Sky 9 from the people above, so I’ll keep this short and sweet — I got a pair in wide to review.

What we like about the Mizuno Wave Sky 9

CHAD: The Wave Sky 9 uses what Mizuno calls a Foam Wave, which has multiple midsole densities that are crafted for soft landings and a smooth transition from heel to forefoot. The Enerzy NXT foam underneath the foot is a great blend of cushioning and bounce, providing the perfect underfoot feeling for a recovery day or easy mileage shoe. Meanwhile, the basic Enerzy on the bottom layer is a good stabilizer.

The upper is made of comfortable, eco-friendly recycled materials, and you always get a checkmark in the upper column if you have a gusseted tongue. The ride is as advertised from Mizuno, soft in the landing in the heels and stable and smooth through the transition.

LINDSAY: Mizuno has always been at the forefront of sustainable shoe production, and the Wave Sky 9 is no different. The woven recycled upper material really hugs the foot in a way that keeps you from sliding around without being suffocating. The gusseted tongue is a comfortable level of plush that blends nicely with the cushion around the ankle.

There is a sturdy heel counter that rises borderline too high on the Achilles for me, but it surprisingly didn’t bother me on runs, nor did it leave any blisters. There is no pull tab, but I honestly didn’t even miss it; I slipped in and out of this shoe without needing to untie the laces. No readjustments necessary.

The midsole is a pillow of cushy foam that is equal parts stable and bouncy. You really get the most feedback and energy return from it with a midfoot strike as opposed to toe or heel striking, which is a small benefit to those of us who overstride, because this is a nice negative feedback mechanism (or positive feedback depending on how your mind works).

The outer layer is a durable rubber. I took this shoe out for a few rainy runs and can attest to zero slippage, even on the few sketchy parts of the Baltimore promenade (IYKYK). I got about 30 miles in and haven’t noticed any extensive wear.

CARYN: I’ll admit, it was hard for me to want to put on this super dark knit shoe in the heat and humidity of the mid-Atlantic summer, but lucky for you guys, I survived.

I’ll focus on the foam, because for me, that was the primary upside to this shoe. The Wave Sky’s Foam Wave features a multi-density midsole, which is designed to optimize the heel-to-toe transition. The foam right underfoot, Enerzy NXT, is both soft and responsive. It feels lively and bouncy without being unstable. The shoe overall is pleasant to run in, though it is certainly designed for easy miles. It’s too bulky to really pick up the pace or handle workouts. It could certainly be used for a long run, if the fit is right — more on that below.

WIDE-FOOT JARRETT: The stretch woven upper provided a solid fit in my 2E width. I had a good lockdown with no heel slipping and tons of comfort from the plush gusseted tongue. I thought there was just enough width in the midfoot for me not to have any pressure discomfort. It’s not extremely wide, but I didn’t find it constricting when running. On days I wore the Wave Sky 9 out for casual wear, I did wish I had a little more room towards the end of the day. There were also some toe box troubles (see section below), but nothing causing me to bail early.

Where the Wave Sky 9 really shines is in the Enerzy NXT midsole. I was shocked at how solid it felt to run in. There have been some max cushion shoes that are insanely comfortable, but have zero give back and end up being soul sucking. That’s not the case here. During my easy runs, I particularly appreciated the cushion, which provided just enough bounce to prevent overworking my legs.

What we don’t like about the Mizuno Wave Sky 9

CHAD: Have you ever been skiing? Remember that amazing feeling of taking off your ski boots after hours and hours on the slopes? I’ve never experienced a feeling similar to that when it comes to running shoes until I tried the Wave Sky 9. I took it on a 5-mile easy day run shortly after they arrived, and while I loved the underfoot feel, my feet felt strangled no matter how loosely I tied the shoe.

I felt like I had enough foam under my forefoot and heel, but in the midfoot, I felt like I had nothing underneath my arch. Add in the fact that the upper was incredibly narrow and low volume, my feet were left super achy after each run in the shoe, to the point where two days afterwards, when I went for my long run, they were still bothering me. I can handle a shoe being a bit narrow or can handle it being a bit low volume; however, having both is a recipe for pain.

LINDSAY: I was really relieved to find that the Wave Sky 9 comes in wide. My first couple of runs were a bit uncomfortable in the toe box area, but I do have small bunions. It loosened up a bit over time to the point where I could wear the shoe with only mild discomfort, as opposed to the “get this off me” discomfort. Probably best to get it in wide if you are ever on the border or just prefer a roomier fit.

As I mentioned earlier, the heel counter rises quite high, and in addition to that, the rigidity extends through the medial ankle. It was almost like it was constructed to reduce overpronation. That rubbed me the wrong way if I paid too close attention to it. Not a deal breaker though. I would just recommend trying this one on in a store first if you can help it.

CARYN: Ultimately, I couldn’t actually take this shoe on the full mileage we typically demand to for a review because of the fit. It runs small to the point that lacing it up felt painful (and I have a wide-ish foot, not a true wide). The toe box was so short and narrow that I would need a full size up to offer my dogs even close to enough space. I found the lack of space exacerbated some old injuries, so I didn’t risk it past my 10-mile maiden voyage. If you have a more narrow foot, the shoe could potentially work, but I’d still encourage at least a half size up from your typical size for the best fit from a length perspective.

WIDE-FOOT JARRETT: It’s weird to say, but every time I laced up the Wave Sky 9, I wondered if it was a touch too short. I don’t know if it’s the length or the shallowness of the toe box, but I would immediately think my big toe was near the front. The confusing part is that I had some room and no issues when running.

While there are many aspects I think are solid with this shoe, the price point is somewhat off-putting. At $180, it skews towards the more expensive side of a daily trainer. However, I just don’t get as excited as I should to put on this $180 shoe for a run. The lackluster grey design doesn’t help either. I don’t know if it’s the tariffs or inflation, but $20 less would go a long way.

Final thoughts on the Mizuno Wave Sky 9

CHAD: The “what if” for me in this situation is, “what if this shoe wasn’t so darn narrow and low volume?” I think that if the upper didn’t have those issues, the Wave Sky 9 could be one of the best max-cushion shoes of the year. The underfoot feel is amazing, and perhaps I wouldn’t experience the same issues if I received a 2E wide version, despite having very regular-width feet. However, if you have a low volume or narrow foot, this might be the shoe for you. However, with this shoe coming in at $180, I’d be looking in other directions, such as the New Balance Fresh Foam X More v6 ($155) or the Puma MagMax Nitro ($180).

LINDSAY: Another lovely addition to the Mizuno line of daily trainers. This is easily the softest and bounciest midsole I’ve tried amongst Mizuno shoes. It’s probably my favorite right now, too. Yes, even more than the Mizuno Neo Vista 2, which is another stellar shoe. It’s also $20 cheaper, but both are a bit pricey, in my opinion.

The Mizuno Wave Sky 9 may be max cushion, but don’t be fooled. This shoe can pick up the pace while also keeping you comfortable for the long haul.

CARYN: There’s a ton of potential in the foams used in the Mizuno Wave Sky 9 midsole, but for me, the buck stops there. The fit made it hard for me to truly appreciate the ride of the shoe, which I imagine would be comparable to some other max-cushion favorites. For now, I’d select a variety of other opinions over the Wave Sky 9 — or to be honest, even pick up my old court shoes for a throwback to the good old days.

WIDE-FOOT JARRETT: I had zero expectations with the Mizuno Wave Sky 9, and I think that was very helpful with my conclusion. It surprised me in a good way, and after each run, I always felt like it was a very solid shoe. While the $180 price tag is pretty hefty, the wide width is solid, and I liked the cushioned ride the Enerzy NXT midsole provided. Apparently, everyone had trouble with the standard width. I didn’t think the wide was extremely tight, but it’s not overly roomy. In the end, if you can get a good fit, I’d say the Wave Sky 9 is a sleeper, and I’ve definitely put in more miles than I needed to review, which is always a good sign.

You can pick up the Mizuno Wave Sky 9 for $179 from Running Warehouse (featuring free shipping and 90-day returns) by using the buttons below.