Sunday, March 21, 2021

Mizuno Wave Sky 4 Waveknit Multi Tester Review

Article by Jeff Beck, Dominique and Sam Winebaum

Mizuno Wave Sky 4 Waveknit ($160)

Sam: The Wave Sky 4 is a highly cushioned, protective and stable neutral trainer. It updates one of my favorite “heavy duty” premium trainers of 2019, in fact my favorite in the category that year, the Wave Sky 3 (RTR Review) which while not the lightest had a soft smooth ride with some pep and was one of the first Mizuno to do away with the plastic wave plate substituting a wave like construction of foam layers which worked and worked well. 

The Wave Sky 4 has a similar wave construction and introduces Mizuno’s Enerzy foam as the top layer in the midsole. Energy is said to provide a “softer and more energetic underfoot experience”It also gets a new Waveknit upper. The weight stays nearly the same at 11.32 oz / 321g in my US size 9 sample.

Dominique: This is my first introduction to a Mizuno running shoe.  The Wave Sky 4 Waveknit has been designed to deliver a plush feel ingexperience, which is something I look for in a running shoe. As a rule, I wear the same pair of running shoes for months at a time, especially if it is the right fit for me.  The shoes are firmer than my just retired Hoka Mach 4, which is a bit of a concern as my left heel can be sensitive to changes.  Time to run them! 


  • Dense and firm, but well cushioned - Jeff/Sam
  • Love the lacing system and the WAVEKNIT™upper which keep my feet both securely and comfortably in place-Dominique/Sam
  • Comfortable fit though lengthwise but the shoe size runs low upfront- Dominique
  • Plush feel of the shoe is combined with an energetic platform-Dominique
  • Generous padding around the ankle and plenty of room up to the forefoot-Dominque
  • Great stability shoe without being overly stiff-Dominique
  • Mizuno wave technology works for me: great shock absorption (no issue with heel soreness after 5 runs) and plenty responsive- Dominique
  • Highly protective, stable ride-Sam
  • A totally secure knit upper, comfortable and well wedded to platform-Sam

  • Notably responsive, smooth transitioning agile forefoot for such a “big” shoe-Sam
  • Paces faster than expected. Sam
  • Expected long durability
  • All is right in the world - Mizuno has firm cushion again - Jeff
  • Upper is pared down from last year and more breathable - Jeff


  • Price point is a bit high, although quality is therefor sure- Dominique/Jeff/Sam
  • Old school ride. Dense, quite firm, not much bounce, plenty of cushion Sam/Jeff
  • A bit firmer than I am used to, too firm. Dominique/Sam
  • Shoe runs small and low upfront -- not enough room to wiggle my toes in my regular size 9 Dominique/Sam
  • Old school ride. Dense, quite firm, not much bounce, plenty of cushion Sam/Jeff
  • Heavy for a modern trainer at 11.32 oz-Sam
  • Half size small due to low toe box-Sam
  • Toebox is criminally low - Jeff

Tester Profiles

Jeff is the token slow runner of the RTR lineup, and as such his viewpoints on shoe and gear can differ from those who routinely finish marathons in three hours or less. Jeff runs 30 miles per week on roads and trails around Denver, CO (and sometimes on the treadmill when the weather gets too much for a Phoenix native). Jeff only got into running in his 30s, as a result his career PR's are 4:07 for the marathon and 5K at 23:39. Jeff has finished several ultra marathons, from 50K up to 50 miles, and is still debating if he wants to go down that road again.

Dominique has run for over 40 years, consistently about 25 miles per week at paces between 10 and 11 minute miles. She races rarely, but always surprises more hard core runners in her age group when she does. She has a 1985 marathon PR of 3:16 in her second marathon which at the time put her on the top 10 Swiss women’s lists.

Sam is the Editor and Founder of Road Trail Run. He is 63 with a 2018 3:40 Boston qualifier. Sam has been running for over 48 years and has a 2:28 marathon PR. These days he runs halves in the just sub 1:40 range training 30-40 miles per week mostly at moderate paces on the roads and trails of New Hampshire and Utah. He is 5’9” tall and weighs about 164 lbs.


Weight: men's  11.32 oz / 321g (US9)  /  women's / (US8)

  Samples: men’s 11.32 oz / 321g (US9) | 12.2 oz/347g (US10.5)

Stack Height: 33mm heel / 23mm forefoot, 10 mm drop

Available now.


First Impressions and Fit

Dominique: The Sky Wave 4 runs smaller than my true to size, however, I am able to run in them.  As a long time runner in my early sixties, I look for comfort, protection, and a bit of performance in a shoe.  The Mizuno Wave Sky 4 Waveknit seems to be a good match for me -- and this after 8 runs and 40 miles.  It is an attractive looking shoe with an interesting wavelike pattern from the upper to the midsole.  

This is not the most lightweight of shoes, however, it is not an issue for me given that I run at a fairly slow pace (11 minute/mile).  This is probably the most comfortable “stability” shoe (although Mizuno calls it neutral as there are no overt stability elements such as posts) I have ever tried.  The construction of the midsole with its wave technology appeals to me.  It has a fairly high drop (10mm), which noticeably impacts the ride, but in a positive way as I am a heel striker. 

Jeff: I reviewed, and enjoyed the Wave Sky 3, and initially dismissed the 4 as a minor upper update with few other changes. I could not have been more wrong. While the upper was actually completely reworked, the midsole and ride were very different right out of the gate, with a much firmer midsole, even classic Mizuno levels of firm. 

Fitwise, I am the outlier here, because I still get a full thumb’s width in front of my big toe with my standard 10.5 - however, the toebox has a very low low ceiling. Width is fine up front, but there is so little room for my toes, I had to cut a few runs short, around five miles, for fear of losing a toenail.

Sam: Initially I thought my half size up pair was too small, and as Jeff did, I experienced some over the toes pressure from the denser and low over the toes knit. The shoe stretched out as knits do during the first run and during each run. I would still size up a half here but still beware if you enjoy overhead toe room up front. 

As always with Mizuno the build quality is impeccable. My two shoes weighed exactly the same to the gram as did the Inspire 17 I am also testing. 

My gray, black, white and yellow colorway is classy with just enough color through the top Enerzy foam layer, heel counter overlay and highlights to liven things up. The 3D knit pattern at midfoot is effective in locking the midfoot and in conjunction with the elastic thin gusset tongue contrasts with the more open the  knit right over the toes and the stout knit around the toe bumper.  The whole package’s visuals speak to protection, durability, and zoned support with a hint from the wave patterns on the upper and midsole that they can also move along. The weight at 11.32 oz in my US9 gave pause but “big” shoes can move along when engineered correctly.


Dominique: The WAVEKNIT™upper is very comfortable and is tightly knit for a secure fit. The well designed shoelace system with eyelets spread out in a wavelike notched pattern keeps the foot comfortably in place.  A gusseted tongue with thin soft padding contours the upper foot securely. 

The toebox is widest around the ball of the foot and becomes narrower around the toes.  A comfortable upper with a secure fit and a durable knit.  

Jeff: The second iteration of Waveknit in the Sky has done a lot of good for this shoe. Last year’s upper was very thick in every aspect, and it really held onto a lot of heat. This shoe’s upper is much thinner, and much more breathable. I appreciate the thinner tongue. Just like last year's version this shoe has a very premium quality to it. Mizuno’s finishing touches are hard to quantify, but I have been consistently impressed with their level of quality for years - and this shoe is no different. However, the thinner knit does not give the shoe much stretch up front, and it is a deal killer for me. 

The stripe that outlines the toebox is right where each big toe sits, and there is almost zero vertical give, creating lots of issues around the biggest digits for me. I don’t have any width complaints, but this is one of the few toeboxes that is very limited vertically.

Sam: The Sky 4 has a knit upper that mostly works well for me.  The combination of 3D midfoot bands and an excellent thin slightly tongue with slightly stretchy gusset do a great job locking down the midfoot while the heavily reinforced heel counter extending far forward provides a very solid heel hold. 

A solid heel counter is key in a knit shoe and here Mizuno does it right. However its mass must add to weight as it is not only thick and firm but it extends unusually high and far forward.

All of us noted the toe bumper area and the low over the toes dense construction there.  I concur that the knit is overdense up front as steps down in height if you will over the toes when it should step up for volume while its coverage including to the sides is too high and extensive. 

I did not experience any particular issues but always had a sense of needing more front of toe box  volume and give and even in my half size up pair and didn’t provide an ideal fit there.  


Dominique:I am pleasantly surprised by the plush feel of the shoe and its energetic platform.  New to Mizuno wave technology I feel reassured that I am running in a shoe that provides great shock absorption. A midsole made of three different types of foam: U4icX, Yellow XPOP and MIZUNO ENERZY.   The yellow XPOP is a strip at the center which helps confer the shoe its bounciness.  Stacked in a wavelike pattern, the combined foams provide a plush feel cushion, great shock absorption, stability, and a responsive ride.  However, it is a bit firm.

Jeff: If it didn’t mean completely destroying the shoe, I’d love to cut it open with a bandsaw and get a feel for how the different midsole materials are used. The ENERZY is the dark blue top layer, while U4icX is the offwhite, and XPOP is the visible yellow along the exposed bottom, but I’m really curious if XPOP permeates through. 

Editor’s Note: While we do not have a cut away of the Sky 4 we believe the construction is similar to the Sky 3 shown below with the XPOP the yellow layer.

Regardless, Mizuno found a way to put three different foams together, and the result is much firmer than anticipated. This is my fourth Mizuno shoe to boast ENERZY midsole (Wave Rider 24, Wave Rider Neo, Wave Sky Neo) and this is easily the firmest of the group. 

While it is billed as a neutral shoe, I agree with Dominique, there is a lot of inherent stability here. That said, for the size and weight of the shoe, the forefoot has adequate cushioning, not really exceptional cushioning, which I’d expect of a shoe with that much weight to it.

Sam: While it has  been a while I was surprised by the change in feel of this midsole from the Sky 3’s, a midsole I really enjoyed for its soft and quite energetic feel, despite the shoe’s bulk. I was expecting much more of the same in terms of an energetic return but found something different.

What I experienced was a very protective, highly cushioned midsole that was quite dense and firm in feel.  At the heel I could sense the XPOP providing some “internal” slight bounce. By internal I mean that surrounding it the Enerzy top layer and U4icX bottom layer provide a very stable “cage” so this should be a great shoe for heavier heel strikers.

To pressing, the yellow Enerzy layer actually feels slightly firmer than the lower U4icX layer which surprises me as I expected the Enerzy to provide a bouncy softer layer directly underfoot. 

The stability oriented Inspire 17 I am also now testing reverses the layers putting Enerzy as the bottom layer and to the touch the Enerzy there is softer than the U4icX above with a far deeper rear decoupling groove. Even with a plastic Wave in the mix the landings and the initial transitions more pleasing and smoother helped along by 2mm more drop at a big 12mm for Inspire 17.

I also note how “squared off the Sky Wave 4 medial rear landing is.

and how shallow its crash pad groove in comparison to the Inspire is which for me affects the smoothness of the transition off the heel leading to a very stable if a bit ponderous effect.

I guess as with say FueCell from New Balance Enerzy is more a “collection” of different experiences and here heavy duty heel stability and a firm dense yet extremely well cushioned feel is what was decided on and delivered. I miss the feel of the Sky 3 in that respect as it provided plenty of all of the above without feeling so dense and firm.

The stack height is 33/23. I have not touched on the forefoot yet. It is also densely cushioned and quite stiff with a single to the rear flex point and extensive rubber in the mix and at 23mm fairly low. I did experience some forefoot fatigue after 10 miles during a 12 mile run which I attribute to: a relatively low forefoot stack height, firmness of the foam, extensive rubber, and flex geometry.  


Jeff: I can say confidently that Mizuno changed virtually nothing about the outsole from the 3, and that’s not a problem. It’s a very durable and grippy rubber, and there are enough gaps in the rubber to keep the shoe from being an inflexible brick. I will warn that the shoe creates a weird gripping noise before it is broken in and the rubber has some wear on it. Not a problem as much as just an audio oddity.

Sam: The outsole speaks to coverage and durability and I expect it will deliver many hundreds of miles of heavy duty use. 

I do think its coverage is overly extensive particularly at the midfoot which while it contributes to inherent stability adds to the weight and makes transitions less than snappy if smooth and consistent.  One can contrast this outsole to the Inspire 17's, an actual stability focused shoe with its far deeper carved out central cavity,  ong continuous decoupling groove, and smaller more svelte yet still very considerable lug pattern. 

Not sure why this midsole/outsole geometry wasn’t used in similar fashion on the Sky Wave as the resulting ride of the Inspire is much more to my preference and I usually don’t care for stability shoes. 


Dominique What started as a lukewarm attitude toward the Wave Sky 4 WAVEKNIT has morphed into reassurance that I can actually safely enjoy running in a stiffer and more stable shoe. The Mizuno wave technology creates a smooth running experience with a forward motion of the foot from heel to toe.  I am happy when I can “break” under 11 min/mile and sometimes I credit the shoe I am wearing for a small surge in speed in my running routine.  This is the case with Sky 4. 

Jeff: Smooth and firm, the Sky 4 has a very traditional Mizuno ride to it. It doesn’t embrace the bounce like so many other shoes out today, but not everyone appreciates a bouncy ride. Instead it has a very smooth transition and a very reassuring protection that doesn’t completely eliminate ground feel, just tone it down a little bit.

Sam: The ride here is all about maximum heel protection and stability. There is plenty of cushion at the rear but it is dense and not very bouncy and while smooth and also incredibly consistent the transitions and toe offs lack much joy. 

This said the consistency and smoothness is appreciated as in the end I was surprised that my paces were faster than expected if the ride was not particularly exciting and for sure not as exciting as the Sky 3’s was. It is not a plodder or awkward in ride. It's conservative and steady. My longest run in them was 12 miles which is far for me these days and I had minimal if no soreness the next day even if my forefoot was a bit tired towards the end  of the run. This makes it a very fine recovery run shoe for me where I don’t want to think about form or pace much but unfortunately it is not as much fun to do those kinds of runs in as was its predecessor. 

Conclusions and Recommendations


I have been pleasantly surprised by the Wave Sky 4 Waveknit, my first introduction to a Mizuno running shoe.   It delivers on many fronts for me: a comfortable shoe with great protection, plush feel and energetic ride, and a shoe that is attractive looking and built for durability.  I think it is a great option if one is looking for a near stability shoe.  

In fact, running in a stability shoe like the Wave Sky 4 Waveknit has been a much better experience than running in the stabilty Hoka Arahi which had a yet firmer heel -- and I do like running in Hoka!  The price point is a bit high at $160, however, durability should help offset the cost.  As much as I liked running in the Wave Sky 4 Waveknit, I still would go back to running in a Hoka Mach 4, as this has been my favorite shoe over the past year.  

Dominique 9 /10

Comfort 9; Performance 9; Overall shoe design 9

Jeff: I was surprised how much a shoe that looks like last year’s model could be so different. The midsole has changed, not necessarily better or worse, just denser, firmer, and also smoother. The upper has gotten thinner and more breathable, but the low ceiling over the toes was a major issue for me. While it is a very solid easy day cruiser, the $160 price point feels high for the performance, though the mixture of firm midsole and stout outsole means you will get lots of miles per dollar. My biggest issue is that those miles won’t be all that remarkable. There’s a lot going for it, but it feels like it is a few years late to the party in performance.

Jeff’s Score 6.5 out of 10

Ride: 7 (50%) Fit: 5 (30%) Value: 7 (15%) Style: 9 (5%)

Sam: The Sky 4 is what it is. A super durable, consistent riding premium daily trainer. The ride lacks excitement but gets the job done with dense, firmer, well cushioned protection. It seems Mizuno went with a firmer less energetic overall cushion experience than ideal for me.

But for the front fit we all commented on, it has a very well executed knit upper that is comfortable and secure. I score Value based not so much on my preferences but for those who just want a quality, long lasting shoe that will get them through many miles of moderate distance, moderate pace miles. You will not get into trouble in this shoe be it in terms of stability or overly fast day in day out paces and that can be a good thing,

I score it considerably lower than its predecessor as it loses the noticeably more energetic and softer ride of the Sky 3. It also doesn’t measure up for me to its more stability oriented cousin the Inspire 17 which actually has a softer more dynamic ride for this usually neutral shoe runner, 

Sam’s Score: 8.53 / 10

Ride 8.3: (50%) Fit: 8.6 (30%) Value: 9 (15%) Style: 9(5%)

Road Scoring Rubric


Index to all RTR reviews: HERE

Mizuno Wave Sky Neo  (RTR Review)

Jeff: Mizuno’s even more premium shoe that was never released in the US abandons the triple material midsole and sticks with ENERZY throughout, with a more streamlined knit upper. The result is surprisingly a heavier shoe, albeit one with much more bounce than the Sky 4, and runs even smoother. Exchange rates make the price fluctuate, but if you are looking for an enjoyable ride in a big Mizuno shoe, track down the Neo.

Saucony Endorphin Shift (RTR Review)

Jeff: Saucony’s trainer variant of the Endorphin line has a higher stack and more cushion, much more pronounced rocker, and though Saucony’s PWRRUN midsole, while it is very firm, it’s a little softer than the Sky. It also has a more agreeable fit throughout, especially around the toes. The Sky will likely last more miles, and has a more premium feel to it, but I’d save the $20 and go with the Shift.

Sam: I agree with Jeff that the Endorphin Shift is about as firm but has a superior geometry, is lighter, has considerably more forefoot cushion, and a much more dynamic roll to toe off.  It is a much more versatile shoe.

ASICS GEL-Nimbus 23 (RTR Review)

Jeff: As more and more daily trainers adopt lightweight super bouncy foams and feel like they are jumping into the 22nd century, these two feel like traditionalists in a sea of new ideas. Both run very smooth, and have solid cushioning. I prefer the extra bit of cushioning underfoot in the Sky, but prefer the fit and feel of the Nimbus. If toebox height has never been a concern for you, go Sky, otherwise, go Nimbus.

Fresh Foam More v3 (RTR Review)

Jeff: One of the softest shoes out there, the FFMv3 is on the opposite end of the scale from the Sky. But while the Sky has a dense ride that provides a little pop at toe off, the FFMv3 is all about muting the ground, performance be damned. If you want soft to the point of mushy, the More is all you, otherwise, check out the Sky.

Sam: I agree with Jeff that the More v3 is much softer and has a far more muted ground feel. A very broad platform as the Sky 4 has, it also has plenty of inherent stability and is 1.3 oz lighter  Once you step on the gas the More v3 for me has a super bouncy fun take off that contrasts with the stiffer wave like forward motion of the Sky 4. Clear nod to the More for me.

Nike ZoomX Invincible Run (RTR Review)

Jeff: On paper these two should be pretty close, but actually they’re incredibly different. The Invincible has bounce unlike any other shoe out there, compared to the profound lack of bounce in the Sky. The Nike is nearly 2 ounces lighter, but runs even lighter than that, with a fun rebound on every foot fall. While they are pricy at $180, it is the best $20 up charge you can spend.

Sam: I agree with Jeff that these two couldn’t be more different in ride characteristics. Soft bounce and plenty of cushion vs. deep, dense, firmer cushion. The Sky 4 is quite a bit more stable and “safer” for easy miles especially if you need a touch of stability and I expect will be more durable in the long run but won't handle the long runs or shorter faster ones nearly as well or with as much fun in the mix.

Nike React Infinity (RTR Review)

Jeff: Nike’s React foam is much closer to a performance faster feel than the three foam amalgamation that the Mizuno brings to the table. Unfortunately the React Infinity also has exaggerated heel and midfoot support that puts lots of pressure into the arch. I kept waiting for it to go away, but after 80+ miles it never did. Both are solid shoes with fatal flaws, low toebox for the Sky and arch pressure/pain in the Infinity, ultimately, give me the Sky.

Sam: There are several ways to get a touch of stability and I much prefer the rail less approach of the Wave Sky here. Those overly long rails in the Nike, on both sides no less,  get in the way of my transitions. While the Nike is considerably lighter, the Mizuno still gets a very slight nod here and if we were comparing to the Wave Sky 3 a huge nod. 

Tested samples were provided at no charge for review purposes. No other compensation was received by RTR or the authors for this review from Mizuno. The opinions herein are entirely the authors'.

Comments and Questions Welcome Below!
Please let us know mileage, paces, race distances, and current preferred shoes

RoadTrailRun receives a commission on purchases at the stores below.
Your purchases help support RoadTrailRun. Thanks!

Available Now!
Men's & Women's SHOP HERE
FREE 2 Day Shipping EASY No Sweat Returns
Available Now!
Men's & Women's SHOP HERE
Available Now!
Available Now!
Men's & Women's SHOP HERE
Join VIP Family, Get Free Shipping and 15% in VIP Benefits on every order, Details here

Available Now!
Men's & Women's SHOP HERE

FREE Shipping on most orders over $40


Please Like and Follow RoadTrailRun
Facebook:  Instagram: @roadtrailrun
Twitter: @RoadTrailRun You Tube: @RoadTrailRun


Anonymous said...

Road Trail Run’s reviews are among my favorites. You guys do a consistently great job. I know this isn’t a review of Nike’s ZoomX Invincible, but I hope you won’t mind me asking... Is the Invincible a stability shoe or is it a neutral daily trainer with some mild stability elements? And is it an appropriate easy day and long run shoe for someone who is a midfoot striker and a supinator with a wide foot? Or should I consider some other possibilities? Thanks a lot for your help!

dadaya said...

Nice shoes! I wish i can ever afford it for my son! I made a decission last week - to change my resume and find a better job. is the best resume writing service. professional resume writers are working for you!

semmtex said...

I own one and its pretty stable for its stack but no stability shoe at all.

Anonymous said...

Thanks for the great review - just wanted to point out Mizuno actually put the Enerzy label on the wrong midsole layer, which is why you felt the top layer to be firmer than exepected. ENERZY is the lower full length layer replacing the U4ICX of the Wave Sky 3, U4IC forms the top layer unchanged from the Sky 3), and XPOP (which copies Puma HYBRID that came first!) is sandwiched in between. Enerzy softens the ride a little and helps with a faster transition throughout the shoe, U4ic acts as a stabilizer for the softer foam and XPOP gives the bouncing sensation that one experiences with the shoe.

Anonymous said...

Re weight of 11.32, mizumo spec says mens size 10 is 10 0z.

Sam Winebaum said...

Hi Anonymous,
We weighed our sample at that is what we got.
Sam, Editor