NIKE Men's Air Zoom Structure 21 Running Shoes

Product Information

The Structure’s midsole design has gone through a raft of changes recently. Just over a couple of years ago, the Structure had a quad-density midsole. This included three foam densities of the main midsole, plus the hard stabilizer underneath the arch. In case if you found the last year’s Structure 20’s ride to be hard on your feet, consider the list of alternatives at the end of this review. PROS AND CONS

However, the Zoom Structure 21 is significantly lighter than the 20. The heavier weight of the latter means that users are more likely to suffer from foot fatigue. The Flymesh upper of the 20th version provides structural support while promoting air circulation throughout the shoe. In contrast, the 21st iteration features a lightweight seamless wrap-knit mesh which envelops the foot and expands to mould around the shape of the foot for a second-skin fit. Alternative Nike Running Shoes Given the overall firm nature of the midsole, the ride is fairly supportive. Unlike some of the older Structure (17, 19) models, the 21 has minimal ride bias towards the outer side. SUMMARY, AND CHANGES BETWEEN THE STRUCTURE 20 AND STRUCTURE 21 When it comes to support, the Structure 25 is currently the most supportive trainer in the Nike lineup. I’m a mild overpronator with flat feet and I find it stable but the prominent arch is a bit too overbearing. I think it will provide enough support for most overpronators but it’s more suited to runners with high arches. Expect 400 miles of life from the Structure 21, with the wear and tear of the midsole cushioning and outsole happening in a gradual fashion. UPPER FIT AND FEEL An inner sleeve is attached to the tongue, so the arch-band strap is sandwiched between the outer upper and the inner sleeve.

Nike Zoom Structure 21 Sole Unit

From the outside, the Structure 21’s midsole appears to have more than two densities. But that effect is produced by the midsole paint rather than separate foam sections. For reasons best known to Nike, the Zoom Structure has rarely had a plushly padded tongue or heel lining. Thankfully, the Structure 20’s tongue quilting is nowhere as bad as the Structure 18. This update got rid of the overly skewed ride behavior of the Structure 19. The new design was also easy on the foot, as the under-arch lost the pointy feeling. Nothing has changed on the midsole this year as the Structure 21 carries forward the same design. Structure 21 rides very similarly to the ASICS GT-1000 6, with a bit more flexibility in toebox upper fit; the heel fit also gives a touch more room. So all in all, the fit is closest to ASICS’ GT-2000 series. I’ve enjoyed running in HOKA’S, but for some reason a higher ride in this Nike never lost its awkward feel.

The rearfoot rides flat because there’s nothing there except for the dual-density foam and the outsole. Though the open foam area below the heel plus the removable insole helps with the cushioning, the rearfoot is noticeably firm. The new Structure is nearly an ounce lighter than its predecessor, thanks to a new knitting technique, with the same magical balance of stability and cushioning—not too stiff but with the added support overpronators need. If you’re looking for a stable, relatively lightweight shoe that can handle a ton of miles, well, you don’t have to look any further. Runner’s World Wear Testers Say Two shoes from New Balance complement the Structure 21 perfectly. The first is the newly released 1260V7 – a cushioned stability model. The second shoe is the 1500V3, one of our favorite road racers which combine lightweight cushioning with mild support. SIMILAR MID-PRICED SUPPORT SHOES This workout session cemented in my mind that Structure is more suited for mid to long distance runs than speedwork and that the more loose heel really does bother me. A lower drop seems to encourage runners onto their toes while at the same time limits the range of motion of the Achilles.

The Structure 23 felt like a supportive neutral trainer, not a “true” stability trainer. I reviewed both the Structure 23 and 24 (the 24 was only an upper update). I found them to be the best versions of the Structure to date because they felt stable and supportive without the firm ride or poking arch sensation that you normally associate with stability trainers. Structure is also a competitor to the Saucony Guide, Brooks Adrenaline GTS, and the Mizuno Wave Inspire. You’ll get a similar upper fit from these shoes, but the differences in offset provide varied underfoot experiences. The Structure 25 won’t be staying in my rotation. It’s a decent running shoe with a good price but I’m not a fan of the prominent arch because of my flat feet. I prefer other stability features like a wide base or a plate. I also find that it has a flat, boring ride like a shoe from 6 years ago. To spice up a foreboding 800’s workout this morning, I decided to run some of the scheduled repeats in Structure 21 and the rest in my favorite speed shoe, Nike Odyssey 2, to see if the Structure being half an ounce lighter made a difference. The lacing panel and the Flywire areas are now reinforced with a thinner and transparent laminate which also helps reduce weight.

The outsole rubber is laid out in a familiar format. The outer side has the ‘crash rail’ strip with multiple flex grooves, a design first used on the Pegasus 31.The Structure 25 is more of a stability trainer than the 2 previous Structure versions. It has an extra heel clip, more arch support and it also has a firmer ride which results in less lean bias. The heel has a hard counter which is non-collapsible, and the toe-box has a flexible internal bumper. Saucony Guide is 2mm lower in heel-toe drop with 8mm as opposed to Structure and GT-2000’s 10mm, with Adrenaline and Wave Inspire coming in at 12mm.

The laces are now flat instead of round. These flat laces pass better through the strap-based cinching system. The Structure 21 uses a strapping system (or the internal ‘arch-band’ in Nike-speak) which was also used on the 20. The Streak 6 is a lightweight Nike model fitting for shorter road races and distances for up to a half marathon. There are other subtle changes, all of them for the better. The upper has larger vented areas. The forefoot breathes better, and so does the rearfoot which now gets vented sections over the Flywire cords.The Structure is Nike’s support shoe with a traditional design. This means that the dual-density midsole has a very firm inner side and a slightly less firm outer side. The Structure 20 balanced the two different levels of firmness extremely well. The Structure 21 has an identical midsole, so the ride exhibits the same qualities. DESIGN AND MATERIALS The rest of the upper fits beautifully. The midfoot fit is far superior to the Flywire-based cinching of the Structure 18 and 19. My podiatrist informed me that one’s preference in drop height of a shoe relates to one’s Achilles flexibility—but no two people are alike in terms of an exact “if this then that” diagnosis: you’ll have to try out a few different types to see what really works for you. Nike Zoom Structure 21 General Info