Mizuno Sky Prime Review

The key element of the Mizuno Sky Prime's performance is the dual midsole composition. Mizuno has paired a MIZUNO ENERZY NXT+ foam (nitrogen-infused PEBA) with a MIZUNO ENERZY NXT foam (EVA), giving you the benefits of both materials in one smooth ride. We found this combination of foams to be fantastically light and comfortable underfoot, but they also maintained just enough responsiveness and firmness to be runnable.

Close to our foot, the nitrogen-infused PEBA MIZUNO ENERZY NXT+ layer delivered a lightweight, springy feel that compressed well and let us "sink into" the shoe a bit, as we'd expect in a recovery shoe. And yet, after compressing, the shoe responded well with enhanced energy return and stayed lively and responsive.

Closer to the ground, the EVA-based MIZUNO ENERZY NXT foam added the structure and stability we needed to help balance the softness of the PEBA layer. Overall, we felt like the shoes worked well with our mechanics, and we loved them for double days and slow runs on fatigued legs. On one run, we even managed to bring the pace down to 4:00 per kilometre, with the shoes feeling responsive enough to support the effort.

In a shoe so focused on plushness and recovery, it makes sense that "comfort" is going to get top marks also. We loved the breathable upper material, and the way that they seemed to embrace any sock choice or lockdown we utilised. 

But it was the underfoot experience that really glowed. As mentioned in the performance section of this review, the dual combination of foams seemed to work exactly as intended. They stayed relatively lightweight (for the max-stacked category) and provided a plush sinking-in feeling that felt good on tired legs, but which wasn't SO compressive as to feel sandbag-y. The lower stack of ENERZY NXT foam kicked in at just the right time to keep things feeling runnable.

And here's where we finally had some issues with the Mizuno Sky Prime. Though the comfort and performance sections felt practically flawless, the snug fit, and potentially short length of the shoes left our team divided.

For Amelio, no issues came to light. He has a narrow foot and reported a snug fit of the shoe, but for him it was a good level of snugness. The lockdown and lacing options offered plenty of room for adjustment, and the upper material stretched and flexed well enough to avoid issues with foot swelling later in runs. For him, the shoe offered security where he wanted it.

Breahna, on the other hand, found the shoes to be too restrictive to wear for extended periods of time. Though they felt narrow throughout (like Amelio noted), the biggest issue for her was the toe box. Her toes felt cramped, both from the toe box's shallow ceiling and from the shoe's overall length. Sizing up a half size helped to alleviate the issue, but the fit still wasn't Breahna's favourite.

In the end, if you have a wider-width foot, or have had length-based issues with shoes in the past, you may want to consider ordering a half size bigger than your default with the Sky Prime. We had eight different people try the shoe on throughout the office, and only one tester had issues with the fit. So, it seems like the Sky Prime will work for more people than not. But especially with a recovery shoe, having a little extra space is going to be preferable in the long run over too little space.

Releasing two recovery shoes on the same day necessitates comparison. For us, the Mizuno Sky Prime wins if you're looking for a recovery shoe that feels great but can also pick up the pace a bit. The second layer of denser foam underfoot keeps us moving forward. The ASICS Slowcush wins, though, if you JUST want to stay slow and steady. It's a pure, uninterrupted helping of marshmallow-y goodness that struggles to pick up the pace, but thrives in its element.