Mizuno Wave Sky 5 vs 4 Comparison Shoe Review

by Sportitude
1 Sep 2021

Josh reviews the neutral high mileage and ultra-cushioned Mizuno Wave Sky 5 running shoes, explains why he's a big fan and identifies the updates that set them apart from their predecessor, the Mizuno Wave Sky 4.

Mizuno have shaved off extra weight, offering harder wearing rubber at the high-impact zone of the heel while reducing rubber at the midfoot to keep you feeling protected where it counts, yet lighter on your feet.

To accommodate the new mild rocker at the forefoot, Mizuno have reduced the heel-to-toe gradient by 2mm to ensure a smooth and more effortless transition. The midsole is everything but simple, offering a combination of foams including a top layer of Mizuno U4icX, bottom layer of Mizuno Enerzy and the new, super responsive Enerzy Core in between. On paper it may sound overkill, but when putting foot to pavement it provides cushioning when and where you need it for your long runs.

A minimalist stretch woven upper with premium materials provides the breathability and foot-conforming fit you need to focus on the road. A gusseted tongue and supportive internal heel counter keep your feet locked onto the midsole, allowing it to work its magic to create a floating sensation and protect your feet on every impact.

Check out the review with full transcript below.

Hey guys, Josh here from Sportitude Running and it's shoe review time and we're going to be talking about the new Mizuno Wave Sky 5. This shoe has just landed mid-August 2021 and the hype is real.

There's a lot that Mizuno have done regarding the change from the Mizuno Wave Sky 4 to the Mizuno Wave Sky 5 and in my opinion there's a lot to like about this shoe.

In today's review we won't leave anything out. We're going to talk about the outsole, midsole and the upper. We’ll profile the foot type and runner that could be considering this shoe and give you all the information you need to potentially throw this into your shoe rotation. Without further ado let's get stuck in.

Runner Profile

Before we dial into the engineering features of the Mizuno Wave Sky 5 let's talk about the foot type that this shoe is catering for. It’s a neutral foot type, so nothing has changed with the Wave Sky franchise. They're obviously sticking this in as their premium high cushioned neutral offering.

Being neutral, it means that no arch support has been executed on the medial side. When we're looking at a neutral runner the foot will have a slightly higher arch, so there's a bit of real estate between the arch and the ground.

For this runner coming through their gait cycle they'll either land on their heel or midfoot but as they transition through the central part of their midstance phase, there won't be much of a tendency to favour that medial side. This runner will stay either through the central part of their foot or ever so slightly they might tilt towards the outside or supinate as they exit out of their gait cycle.

With that in mind and with what this shoe is targeting being a max cushioned or high mileage running shoe, there is plenty of protection underneath the foot. The runner buying this shoe is going to be someone that's looking for a mileage shoe, so you're doing plenty of long runs out on the road or you're seeking a bit more protection underneath your body.

It's light enough and you can certainly do some progressive runs in it. I have done progressive runs in my pair and it felt absolutely fine at a slightly quicker pace. With that being said, this running shoe is not designed for someone who is going to throw a lightweight shoe on their foot and really want to smash some PBs or put tempo runs into your weekly training program. This is more for your mileage running to do plenty of Ks out on the road.


Let’s get into the engineering of the Mizuno Wave Sky 5. First things first, let's talk all things outsole. Underneath the shoe it is full ground contact from the heel through to the forefoot with a little bit of exposed foam underneath. I wouldn't say that's going to cause any grief for any runners. You may see a little bit of unusual wear but that's A-OK. Overtime you're going to expect wear underneath your shoe.

At the back we have a slightly harder wearing rubber and that's been strategically placed there to cater for that heel striker. If you happen to be a midfoot runner you're still going to get plenty of purchase with the ground on that lateral side.

Coming through to the forefoot, this is where I find in combination with the midsole most of the improvements and most of the comfort in this shoe. We have four flex grooves going through the forefoot. There’s plenty of flexibility through the shoe and it’s partly due to the way the midsole is pitched which I’ll explain in two ticks. Four flex grooves from the medial to the lateral side creates a very consistent feel.

In comparison to the Mizuno Wave Sky 4, they again had full ground contact. You can see straightaway there is considerably more rubber on offer in the Wave Sky 4. There are literally no areas through the midfoot where they have taken any rubber out. By reducing the amount of rubber underneath the Wave Sky 5, naturally you're going to also reduce the weight of that part of the shoe which is a great thing.


Let’s talk about the midsole because there is so much going on. We have an 8mm heel-to-toe drop in the Mizuno Wave Sky 5. Last year we had a 10mm heel-to-toe drop so there's a marginal change with that 8mm offset.

Talking about the stack height, we have 37mm in the heel and we have 29mm in the forefoot, so that's where you get the 8mm offset. Last year it was a 33mm heel and 23mm forefoot so that model was closer to the ground but had a more of a pronounced heel-to-toe offset.

In the Mizuno Wave Sky 5 they've increased the stack but reduced the heel-to-toe gradient. The reason is because Mizuno have introduced a little bit more of a rocker through the forefoot which is a great thing.

Having a high heel-to-toe drop and a rocker just wouldn't work and it wouldn't be a consistent feel underneath the body. Dropping the stack height 2mm and offering that rocker through the forefoot means you’re going to get a smoother transition through the whole gait cycle.

Now to talk about the foams because there's three key foams inside this shoe. On the top layer we have the Mizuno U4icX cushioning system which is a technology they've used for a few years now. On the bottom layer we have the Enerzy cushioning system. It's split by the colours, so the top layer being U4icX is navy, the bottom layer being white is the Enerzy foam.

However, the biggest addition to this shoe is the new Enerzy Core which you can see with that little red call-out beneath the shoe. The Enerzy Core is a new patented technology that Mizuno have been working on for a few years now. They've been waiting to introduce it into a shoe and they've done it with the Mizuno Wave Sky 5.

The Enerzy Core runs from the heel right through to the forefoot. It’s a similar concept to what they executed with the XPOP from last year. You can see that subtle yellow piece of foam or that call-out underneath the Wave Sky 4 and that was a polyurethane cushioning system running from the heel through to the forefoot.

Enerzy Core isn't polyurethane, it's a lighter and more responsive foam that they have been able to wedge between the U4icX and the Enerzy and also wedging it into the Mizuno Wave technology. There's a lot to take in with the running shoe regarding what Mizuno have executed with the midsole.

I'd like to use the phrase less is more but that’s not the case with the Mizuno Wave Sky 5. We have a fair bit going on underneath the foot and to be completely honest and transparent with you I was a little bit concerned that there would be too much happening underneath the body.

However, on my first run I was very happy and on my second run, even happier. I've done about 30km in my Mizuno Wave Sky 5 and I can’t fault the midsole, it performs very nicely underneath the foot. It has cushioning in the areas I want to be cushioned.

Being a midfoot runner, I get all the cushioning I require and that impact support. However, my absolute favourite part of this shoe is that little rocker through the forefoot. I feel that my release is nice and smooth and I’m really liking what they've done with the midsole.


Let's talk all things up upper. Mizuno have gone back to the drawing board and have done a couple mild changes to this upper. In their upper less is more. Unlike the midsole, they've executed a very minimalistic fit, feel and function on top which I am a big fan of.

They've called it a smooth stretch woven upper. From just behind the lock lacing system forward you have a really conformed fit. If I must be completely critical it is slightly shallower through the forefoot than what the Mizuno Wave Sky 5 was before with their engineered mesh.

It's a lighter, softer and more breathable upper. They really nailed how it fits, breathes and locks down. Mizuno have really done a great job with the Wave Sky 5.

The other added benefit is the gusseted tongue. The tongue is stitched through the bottom to keep it nice and locked in but there is a gusseted structure on the medial and lateral side.

I am a real fan of gusseted tongues. It does keep your foot locked in and on top of that platform, which is where most the time and effort with the running shoe is put into the engineering. It’s all to do with the midsole so you want to make sure your foot is getting the most out of that cushioning and support. By having a gusseted tongue it keeps your foot nice and secure.

Coming to the back of the shoe, they haven't changed anything with regards to the internal heel counter structure. You have a strong support system at the base of your calcaneus. You can come back to that last eyelet to really lock down your heel inside this shoe.

The other real benefit I must call out is they have ever so slightly changed the amount of memory foam they have on the internal lining.

It’s a small criticism and when I say small, I literally mean small. I personally found the memory foam to be very comfortable in the Mizuno Wave Sky 4 however feedback wise it was probably a little bit too much foam. A lot of runners came back saying, “I like the feel of it, it felt comfortable, but it was just a bit too much foam going on around the back half”.

Mizuno listened and have decreased the amount of foam around the back of the running shoe but by no means have they sacrificed comfort and cushioning. It’s still a very nice fit and feel and the materials they use to secure that foam are premium.

It feels very nice and I haven't experienced any rubbing at the back of this shoe whatsoever, from my first run right through to my run this morning in the Mizuno Wave Sky 5.


Let's talk all things widths with the Mizuno Wave Sky 5. In the men's model we have a standard D width and a slightly broader 2E. In the women's model we have a B standard and a D width on offer, so there’s two widths for both the men's and women's model.

I love it when a brand makes their shoes available in widths. They're catering for that neutral runner but if you happen to be slightly broader foot type and you don't find the standard width comfortable, they have the 2E or D on offer to make them more comfortable.

The Wrap Up

In wrapping up the Mizuno Wave Sky 5, it is slightly lighter with about 15 grams off the men's size 9 and featuring the slightly lower heel-to-toe drop which I like. The 8mm heel-to-toe offset is executed perfectly with that mild rocker through the forefoot. The biggest and most successful change in this shoe is the addition of the Enerzy Core which runs through the Mizuno Wave technology.

I personally find it a little bit softer but with more of a consistent feel. It doesn't matter if I’m striking it through the midfoot or if I happen to drop back towards the heel, you get a consistent feel right underneath the body.

I really think the Wave Sky is trending towards a very attractive shoe. It's going to cater for a few more neutral runners out there and when you're talking about the Mizuno Wave Sky 5 and its other competitors, you're throwing in the Brooks Glycerin 19, Asics Gel Nimbus 23 and maybe the Nike Air Zoom Vomero into a discussion. I feel this shoe is going to fit, feel and function better for a lot more runners out there and I'm a big fan.

If you have been a Mizuno Wave Sky runner and you have feedback on the shoes, be it the Mizuno Wave Sky 4, Mizuno Wave Sky 3 or if you've been lucky enough to try the Mizuno Wave Sky 5, please let us know.

If you have any questions, queries or theories about this shoe or other neutral running shoes out there please contact our Sportitude shoe experts. We'd love to hear from you the runners out there.

Please subscribe to the Sportitude YouTube channel if you haven’t already done so to stay notified and we'll keep knocking out these shoe reviews for you the running community across the world. We love helping you out.

Until next time stay safe, be kind to one another, happy running and we'll see you out on the road. Take care.


  • Support: Neutral
  • Upper: Mesh
  • Midsole: Mizuno U4icX, Mizuno Enerzy, Mizuno Enerzy Core, Mizuno Foam Wave
  • Heel Height: 37mm
  • Forefoot Height: 29mm
  • Offset / Drop: 8mm


  • Weight: 310g / 10.9oz
  • Width: D (standard), 2E (wide)


  • Weight: 260g / 9.2oz
  • Width: B (standard), D (wide)