Facts

  • Terrain
    Terrain

    Road

    Shoes best for road, track and light gravel. See the best road shoes.

    Trail

    Shoes best for trail, off road, mountains and other unstable surfaces. See the best trail shoes.

    Good to know

    As long as you stick to the road or path, and if you want just one running shoe, buy a road running shoe.

  • Arch support
    Arch support

    Neutral / cushion / high arch

    Shoes for runners who do not need any additional arch support (Around 50% of runners). Best for people with normal, high or medium high arches. See the best neutral shoes.

    Stability / overpronation / normal arch

    Shoes for runners who need mild to moderate arch support (Around 45% of runners). Best for runners with a low arch. See the best stability shoes.

    Motion control / severe overpronation / flat feet

    Shoes for runners who needs a lot of arch support. Best for runners with flat feet. See the best motion control shoes.

    Good to know

    - Rule of thumb: If in doubt, buy neutral shoes to avoid injuries.
    - More about arch support in this video.
    - Find your arch type by following steps from this video.

  • Use
    Use

    Daily running

    Cushioned shoes for your daily easy running. Great comfort. See best shoes for daily running.

    Competition

    Lightweight shoes good for races, interval training, tempo runs and fartlek. Here are the best competition running shoes.

    Good to know

    If you want just one pair of shoes, buy a shoe for daily running.

  • Price
    Price
    $120
  • Weight
    Weight
    Men: 10.4oz
    Women: 9oz
  • Heel to toe drop
    Heel to toe drop
    Men: 10mm
    Women: 10mm

    The height difference from the heel to the forefoot, also known as heel drop, toe spring, heel to toe spring or simply drop.

    There are many opinions about what a good heel drop is. We do not recommend any in particular. Lean more in this video.

  • Heel height
    Heel height
    Men: 28mm
    Women: 28mm
  • Forefoot height
    Forefoot height
    Men: 18mm
    Women: 18mm
  • Width
    Width
    Men: normal, wide
    Women: narrow, normal, wide
  • Release date
    Release date
    Jun 2017
  • Special editions
    Special editions
Show more facts

Summary

We spent 10.1 hours reading reviews from experts and users. In summary, this is what runners think:

8 reasons to buy

  • Most runners agreed that the Nike Air Zoom Structure 21 had a suitably lightweight feel.
  • Several runners commended the smooth transition that this shoe offered.
  • A good number of testers felt that it had plenty of cushioning.
  • One user said that the 21st version of the Air Zoom Structure secured the foot better than its predecessor.
  • Many agreed that the style and colorways were stylish.
  • One user was appreciative of the air pockets located in the forefoot. He said that they helped propel him forward during his tempo runs.
  • A majority of the reviewers agreed that the shoe was true-to-size.
  • Several testers observed that the toe box had ample space for toe-splay.

4 reasons not to buy

  • One reviewer felt that his heel wasn’t fully supported or stabilized.
  • Another tester said that the shoe felt stiff out of the box; she wasn’t glad that she had to break it in.
  • One runner narrated that the angle of the shoe placed downward pressure on the ball of his foot, which resulted in some irritation.
  • A runner said that the insole was not as comfortable as expected.

Bottom line

The Nike Air Zoom Structure 21 is a stability road running shoe that provides moderate support. It has received much-needed upgrades to make it lighter and more comfortable to wear. The responsiveness and cushioning from the previous version have been retained. Those who are fans of the Air Zoom Structure 20 should check this one out.

Rankings

Expert Reviews

Experts are runners, who post reviews at youtube, directly at RunRepeat or at their own websites. Each expert is categorized from level 1 to level 5 based on expertise. See stats on expert reviews and how we calculate scores here.

Are you an expert? Apply to contribute here.

85 / 100 based on 3 expert reviews

  • 96 / 100 | Frank DuCett

    Nike Air Zoom Structure 21: Like a New CORVETTE!

    The Nike Air Zoom Structure 21 has survived for over 20 years in the ultra-competitive running shoe business, not by always being on the leading edge with the latest stuff but, rather by simply using tried and proven technologies, wisely.

    This latest Nike Structure is a middleweight, stability road running shoe that can be compared to such well-known industry standards such as the Brooks Adrenaline GTS 18, and the Asics Kayano 24.

     

    The Express Lane

    For all those readers who are too busy running and, do not have enough time to read a nearly 2,000-word review...I understand, so here is the gist of it all.

    The Nike Zoom Air Structure 21 is a medium weight, fairly stiff, yet responsive stability-support category road running shoe.

    It is well cushioned and, it is very well constructed, with room for your toes and, has proven to be fairly durable.

    History

    Nike was founded in 1964 as Blue Ribbon Sports, in the U.S. State of Oregon and was originally a distributor of the Japanese built Onitsuka Tiger, running shoes, today known as Asics.

    Blue Ribbon Sports became known as Nike in 1971. The name “Nike” was borrowed from the Greek goddess of victory.

    First Impression

    When I first look at any shoe, I take notice of what's most important to me; and this Nike had a roomy forefoot with ample room above my toes.

    The upper mesh material was positioned with great accuracy; both shoes were the precise mirror images of each other. Every part was perfectly lined up, with not a stitch out of place, including the ones under the sock liner where nobody ever looks.

     

    Outsole

    With the "founder's touch" still being evident, the classic and highly effective waffle style sole is still present in most of the outsole…with some minor evolutionary updates.

    The outsole is composed of primarily Duralon rubber, with BRS 1000 (Blue Ribbon Sports) carbon rubber being used in areas of higher abrasion.

    The outsole was said to have been designed for flexibility, with "Deep Anatomical Flex Grooves," however I could not find them. This outsole is simply a well-designed waffle style rubber outsole with a lateral side (outside) full-length rubber pad, which runs from the toe to around the back of the heel.

    This produces a very effective smooth transition and, adds traction. These shoes are actually quite stiff and, initially caused me some concern.

     

    Midsole

    The midsole is the heart of any running shoe, all other parts are simply playing support roles. The midsole is made up of two very well-known, time proven foams… Phylon and Cushlon.

    Nike's Phylon is a lightweight and responsive EVA (ethylene vinyl acetate) foam that has been heated and molded and is used as the medial (inner) side of the outsole, this is the foam that puts this shoe into the stability category.

     

     

    Cushlon is a mix of that very same Phylon material, but with the addition of top-secret rubber additives, this foam is used in the lateral (outer) side of the midsole. This is the foam that gives this shoe its characteristic bounce and liveliness.

    These two foams are fused together in what at one time was called "Dual Fusion," and now renamed the “Dynamic Support System.” I always liked the "Dual Fusion" name; it sounded descriptive and promising to me.

    It is reminiscent of the terms we used in the old HOT ROD days like Dual Exhaust, and Dual Quads. I grew up reading HOTROD Magazines and, they still add to the descriptions I use to define things in today’s modern running world.

    The Nike Structure 21 has a gender-specific crash pad at the bottom of the heel, and along with a variety of colors and sizes, completes all gender-specific considerations.

    There is also a Zoom Air unit placed in just the right location in the forefoot.

    Upper

    These uppers are an example of “Engineering Simplicity.”  

    By using a single piece of monofilament reinforced Engineered Mesh, with a minimum of overlays, Nike created an attractive and streamlined appearance. Some of the overlays are so thin, they look as if they had been painted on, like racing stripes on a sports car; however, they do help lend structure to the uppers.

    The Nike logo is the most prominent overlay, and there is a near total absence of visible stitching; other than those needed to neatly attach the tongue.

    Most of the lacing is fed through loops rather than eyelets; this provides more comfort by disbursing the lace pressure over a wider area…in what they are calling a Strapped-Based-Lacing-System.

    There are four conventional eyelets, towards the rear/top of the tongue that are used in conjunction with the Flywires.

     

     

    There are a total of only 8 Flywires used per shoe, compared to the latest Nike Pegasus 34 which has 24 Flywires per shoe. The Nike Structure 21 is only a partial Flywire equipped shoe, but I think that the most important Flywires are in place, towards the rear of the tongue.

    The Flywires begin their journey at the midsole, and then they move up both sides of the shoe to where the laces are waiting to complete a full wraparound of your foot. The tongue is fairly well padded but not plush and, is secured along its sides; making a lace-stay on the tongue unnecessary.

    There is a thin internal bootie extending all the way forward from both sides of the tongue, keeping the tongue from slipping.

    There is no external heel counter, rather an internal stiffener is used and, surprisingly seems to work well; heel slippage was minimal…for such an inflexible shoe.

    The laces are wide, elastic, and comfortable. However, these laces, sadly, did not stay tied for more than 3 miles; they were replaced before my second run.

     

     

    I generally replace my original laces with reflective laces, for after-dark safety, because getting hit by a car going only 25 miles per hour is like falling from a two-story building!

    Although not a defect, the collar wraps around the back and terminates on either side of the tongue, in an unfinished manner. These unfinished ends tend to hang up the laces.

    Care should also be taken when lacing a shoe with Flywires, it's easy to miss a wire!

    The Fit

    The fit will be somewhat different for each person, however certain aspects are constant. And, for me, I would not change a thing for fear of affecting what has got to be a near perfect ride.

    The forefoot and midfoot conform to the shape of your foot and, the collar holds your heel comfortably with only minor slippage.

    You can feel the FlyWires pull gently up under your arch when tying the laces.

    On the Run

    I stepped into these shoes, very optimistically, after having read several reviews and, having used the "COMPARE" feature found on RunRepeat.com.

    I was very much looking forward to their arrival from California and ran with them the very same storm-threatening day they arrived (Southern Indiana is in Tornado Alley.)

    The Nike Structure 21 is so very blue and, has such panache; I took great care trying to not get them wet or muddy, but I was caught in the rain on the last mile; that first run turned out to be the baptism of my new blue Nikes.

     

     

    This area of the state has no mountain ranges but is fairly hill. The Structure 21 helped me on the hills and, there was plenty of heel cushioning when going down the other side of those hills.

    The forefoot cushioning is amazing; for my weight, these shoes seemed to have been tuned just right.

    Comparisons

    The Structure 21 is not as quiet as the Brooks Ghost 10. Actually, there is a small amount of road noise with each step. However, I have been running faster with these on every run…and not only when being chased by rain! I was very pleased with my new found speed.

    With my Brooks Ghost 10, I was confident that I always had enough cushioning. With the Brooks Launch 3 and 4, I knew I was confident that I had a lightweight and flexible shoe.

    However, with these new blue Nike Structures, I had a different sort of confidence; one that had me checking some of the past half marathons finishing-times of others in my age group!

    I needed to discover what it was that made the Structure 21s so responsive and lively, and I think the answer is to be found primarily in the geometry of this shoe.

    Despite not being very flexible, these shoes tend to roll easily through the gait cycle. There also seemed to be a bit of a push-off provided at the end of my gait, just before toe-off like a diving board at a swimming pool that reacts when pressed down upon.

    This provided a little boost at the end of each step, made possible by the front Zoom Air unit, and where it is placed within the forefoot.

     

     

    On easy long runs, where short strides are in use, I could not ask for a better ride. I suppose a quieter outer sole material would be less durable, and a more flexible forefoot would be less responsive. The Structure 21 is a real good blend of these performance characteristics, and a pleasure to run in.

    This morning was one of those rare days, geese honking overhead, 34 degrees F. and, no wind whatsoever. These shoes are beginning to relax and, they are even beginning to running quieter. They are also wearing well, proving to be very durable.

    These shoes are beginning to loosen up, becoming more compliant after 50 miles, showing very little outer sole wear and, are still amazingly cushioned.

    Specifications

     

           Size Tested        12 D. U.S. / 11 U.K. / 46 E.U., 30 cm.
           Weight        318 gr./  11.2 oz.
           Pronation Category         Support/Stability
           Heel Stack Height         28 mm.
           Forefoot Stack Height         18 mm.
           Heel-Toe Drop         10 mm.
           Arch Height         Med-High.
           Made In          China
           Testers Weight          151 lbs.
           Release Date          June 2017

    Changes since last year's version

    • 22 grams lighter
    • Improved ventilation
    • More durable uppers

    Conclusion

    The Nike Structure 21 is the best shoe I've had in many years, excelling in so many areas, cushioning, fit, transition and I even love the color.

    Personally, I was getting very tired of so many of my favorite brands and models forsaking forefoot and toe box room for streamlined looks. Even simple safety of reflectors; all gone for the sake of savings and, a spreadsheets bottom line.

    Honestly, I do not think our toes are getting any smaller these days and the roads are sure not any less dangerous with today's digitally distracted drivers.

    My conclusion, the Nike Structure 21 is a well-mannered and spirited shoe that will be there for you, during many miles of training and, will not let you down on race day.

    Finally, would I buy this shoe again?  YES!

    Thanks for reading; the rest is up to you. See you at the starting line!

     

    ***My thanks to Runningwarehouse.com for taking back the toe-numbing Asics GT 2000 6 and then the New Balance Zante and sending me the Nike Structure 21 instead. They are well worth the wait!

    This expert has been verified by RunRepeat. Reviews are neutral, unbiased and based on extensive testing.

  • 70 / 100 | Running Shoes Guru

    The Nike Zoom Structure 21 is a shoe that’s been made lighter over its history yet still maintains a sturdy base and secure midfoot to combat the effects of overpronation in a runner’s stride.

  • 90 / 100 | Shoeguide

    Lighter and stronger than the previous version, the Nike Air Zoom Structure 21 offers a great combination of stability, cushioning, responsiveness and durability. A shoe for everyday easy running over any distance.

  • First look / Unboxing | Naperville Running Co

    Naperville Running Co

    Level 1 expert (1-2 reviews)

    2 reviews - average score 86/100

  • First look / Unboxing | Road Runner Sports

    Road Runner Sports

    Level 2 expert (3-5 reviews)

  • First look / Unboxing | lin Roy

    lin Roy

    This YouTube channel has only first look videos - no reviews

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Updates to Nike Air Zoom Structure 21

  • Nike has updated the upper material on the Air Zoom Structure 21. It is now made of a seamless Wrap-knit Mesh which has significantly improved on the ventilation and flexibility. The switch has also reduced the weight of the shoe.
  • The Dynamic Flywire system is still present, but they have been redesigned. More specifically, the wires have been flattened out and widened to reduce the shoe’s weight further, as well as provide a more superior midfoot lockdown compared than the previous design.
  • An internal heel counter that wraps around the Achilles was added. It serves as a structure that gives extra stability to the foot.

Nike Air Zoom Structure 21 size and fit

The Nike Air Zoom Structure 21 has standard shoe measurements. Runners will be able to get the shoe using their usual preference when it comes to length. On the other hand, the width has more options. For men, the standard, wide and extra wide variations are available. For women, the choices are narrow, standard and wide.

Outsole

On the forefoot is the Duralon Blown Rubber. This material is a lightweight synthetic compound that has tiny air pockets introduced during its making. These small pockets help in propelling runners forward during the toe-off phase of the running cycle. Additionally, the Duralon provides a softer underfoot feel while generating traction as the runner goes over different surfaces.

The rest of the outsole is covered by the BRS 1000 carbon rubber. BRS stands for Blue Ribbon Sports. Not only does it supply the bottom of the shoe with enough traction to take on several surfaces, but it was also designed to last long.

Midsole

The 21st version of the Nike Air Zoom Structure has a supportive midsole. It is made up of both Phylon and Cushlon foams which have different densities. Phylon is a soft, core foam wedge while the Cushlon was designed to be the carrier foam, enveloping the central unit and delivering support. The combination of both foam densities makes force distribution equal, resulting in resilient cushioning that’s responsive and dynamic.

The heel part has a segmented crash pad that absorbs impact upon landing and corrects overpronation. Nike made this pad gender-specific so it can cater to specific weights. The dissipation of landing force results in a potentially more efficient transition through the gait cycle.

On the forefoot area is Nike’s Air Zoom technology. Stretched-out tensile fibers were knit inside a pressurized Nike air unit, to produce a snappy rebound. As the runner comes in contact with the ground upon impact, the fibers compress. Then, they spring back to their original state like a rubber band. This mechanic allows runners to feel a forward propulsion during the toe-off.

Upper

The upper is mainly made up of a lightweight Wrap-Knit Mesh. This mesh is composed of a network of monofilament yarns that allow air to pass through its holes, making the inside of the shoe well-ventilated. The mesh also expands quickly, catering to different foot shapes and delivering a custom in-shoe feel.

The Nike check has been embedded as an overlay to give the mesh some structural support. Aside from that, the top part of the shoe is clean and seamless.

Nike’s Dynamic Fit system is made up of widened and flattened Flywire cables, the lacing system, and the interior band around the middle of the foot. The purpose of such a design is to support the arch and to enhance the fit, making it more adaptive.

Inside is an inner mesh bootie which delivers a soft, sock-like feel to the runner. The bootie improves the in-shoe feel and the supportive coverage.

An internal heel counter was added to lock the heel in place minimally. It protects the Achilles from irritation, injury and impact.