The inner straps hug the foot closely, and the newly introduced flat laces pass smoothly through the eyelet straps. Flywire is restricted to the rear, so that takes care of the pressing sensation against the midfoot. 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.

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 The excessive outwards bias or lean of the older Structures (17, 19) is no longer present on the 21. The rearfoot has a bit of an outer bias due to the midsole groove and the beveled heel, but only slightly so. 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 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 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.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.

We had our work cut out for us last year because the Odyssey 2 was the perfect upgrade path from the Structure. This year, the Odyssey is gone so the only way is down. If you don’t require Structure levels of support, then you should look up the Nike Zoom Span 2. When it comes to popularity, the Structure series comes nowhere near the likes of the Pegasus or the Infinity. I personally prefer the Structure to both the Peg and the Infinity because its upper is more padded and the cushioning feels more substantial but I think that most runners still think the Structure is an old school, traditional stability trainer. 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 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 MATERIALSThe Structure 20 simplified the design by toning down the medial post and reducing the number of foam densities to two. Both the tongue and heel are moderately padded. However, runners who’re switching to the Structure from brands such as Saucony and Brooks will notice the utilitarian feel of the Structure. The 21 is my first experience with the Structure line, so I asked a friend of mine who loved the 18th and 19th models what he thought of the 20. Turns out I still much prefer Odyssey for fast running, and the loose fit of Structure 21’s heel was even more apparent after being reminded of the snug heel fit of Odyssey. 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.

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 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.The firm ride quality is distributed evenly from heel to toe, so the progression feels smooth and efficient. The outsole also has the center groove and the side ‘crash rails’ with multiple grooves – features which also assist transitions. The Structure 21 still has Flymesh (as did the 20), but uses a new and lighter version. Nike says that the new Flymesh uses mono-filament yarns which reduce weight yet retain structural strength. The weight claim is true – the Structure 21 sheds nearly a full ounce over the 20. 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 Nike Structure is all about balance. The upper has smooth interiors and fits well. The inner strapping system which was re-introduced on the Structure 20 finds its way into the 21, and that’s a good thing. The Flywire cords are restricted to the rearfoot, and this means that the midfoot is secured entirely by the straps.

There’s plenty of room in the toe-box and forefoot and the fit is true to size. The Structure also comes in multiple widths (2E and 4E) in case the standard D width fits narrow.