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{{DISPLAYTITLE:Nike Vaporfly 4% Review}}
The Nike Vaporfly 4% is a much-hyped shoe, which is based on the shoes Nike developed for their attempt to break the 2-hour marathon. It's an expensive shoe, retailing for $250, and even at that price it's hard to find. There are rumors that Nike are restricting supplies to drive up interest. The shoe is unusual in that it has a carbon fiber plate running through the midsole. Given all the hype, I was not expecting much from the Vaporfly 4%, but there are aspects to the shoe that have really impressed me. I'd say it's a mixture of the awesome and awful, though not in quite the ways I expected. The Vaporfly is hard to rate, as it's a "best of the best" running shoe except for the risk of injury due to its instability. * The shoe has remarkable cushioning for its weight, with my measurements putting it close to the top of the table. I ran with a [[Hoka Clayton]] on one foot and the Vaporfly on the other and the Clayton felt hard and dead by comparison. The Vaporfly uses a new type of foam made of Pebax, a compound that has previously been used in harder materials like Mizuno's Wave Plate. It will be interesting to see this foam in other shoes, especially something closer to a "racing flat". There is a rumored Reebok FloatRide Floatride Racer using Pebax foam, but no details, and I've reviewed the [[Reebok Floatride Run]] which uses Pebax.
* When you wear the shoe, it has an amazing amount of bounce. It's far more than you get in TPU shoes like the [[Altra Escalante]], and feels like there's a spring under your foot. It seems like the carbon fiber plate is acting more as a spring for the rear of the shoe than for toe off. This bounce is immediately obvious, even walking around, and feels different to every other shoe I've tried. Even at the end of a marathon length run the bounce is noticeable and helped me keep up the pace. (Check out my review of the carbon fiber [[VKTRY Insoles]] for comparison.)
* I couldn't detect much difference in toe off from any other shoe, which was disappointing. The forefoot is quite stiff compared with other shoes, but given the forces involved at toe off, this doesn't seem to be enough to make much difference. Of course, a tiny difference in efficiency won't be noticeable immediately, but could make quite a difference to your finish time.
* Initially, the outsole had surprisingly little grip, feeling slick and unsure on anything that isn't a firm surface. After I'd put some miles on them, the grip seemed to improve and was remarkably good, except on gritty asphalt where the grit acts like marbles.
* I found the toe box was not as bad as I expected, though running 20 miles without cutting open the toe box resulted in a minor blister.
Overall, I feel like I'm faster in the Vaporfly than other shoes by a noticeable amount, which is quite astonishing. This is hard to confirm, but my Heart Rate and perceived exertion seem noticeably lower for a given pace and [[Stryd| Stryd Power Estimate]]. On the other hand, I feel like the Vaporfly will increase my has a real risk of injury rate dramatically, putting more adding stress on my to ankles and thus my knees. After many hours of consideration, and hundreds of miles of running, I've rated the Vaporfly as "best of the best" in spite of its many flaws. It's expensive, almost impossible to find, and risks injury, but it's just so good that I think if you can handle the extra stress, it's worth it. {{H:WhatToLookForInShoes}}
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File:Nike Vaporfly 4%-top.jpg|Nike Vaporfly 4% top
* {{H:drop}}. Normally the massive drop of the Vaporfly, which I measured at 12mm, would cause me all sorts of issues when running, but I've got on surprisingly well with it. Part of this might be that the 12mm drop is reduced to 8mm when worn, and might be even less under the impact of running. I have had issues with my heel scraping during the float phase of my stride, but this is not as bad as other shoes. If I'd have had to guess at the drop (something I can generally do fairly well), I'd have put the drop at about 4-5mm. That's more than I'd like, but not problematic.
* {{H:structure}}. The structure of the Vaporfly comes from its carbon fiber plate. There doesn't appear to be any attempt to reduce pronation, and the carbon fiber plate actually seems to actively increase pronation. I have not dissected my pair, but it feels very much like the carbon fiber plate doesn't extend under the ball of the foot. Instead, it seems like the plate runs the full length of the shoe, but only under the four outside metatarsal bones. Towards the end of a marathon length training run the edge of the plate can become quite uncomfortable, and I've had some soreness from it. Under load, the ball of the foot is lower than the other four metatarsal heads, something I normally find when a shoe is worn out due to the midsole foam collapsing.<br/>[[File:Vaporfly (2).jpg|center|thumb|300px|This is the edge of the carbon fiber plate, which seems to be about the same on either side.]]<br/> [[File:Vaporfly (3).jpg|center|thumb|300px|From the side, the profile of the carbon fiber plate follows the purple line I've drawn, not the black line that you might expect.]]
* {{H:flexibility}}. The Vaporfly's carbon fiber plate obviously reduces its flexibility. It's far from the least flexible shoe I've tested, but the carbon fiber plate makes it more of a spring, where most maximally cushioned shoes tend to be rigid. As noted above, I'm surprised how little I noticed the toe off spring. I've tested the [[VKTRY Insoles]], which is an aftermarket carbon fiber plate that you can put in existing shoes. I found the benefits of VKTRY were hard to notice, but it's hard to detect things that can make a significant difference to your running performance. After all, 1% difference in running economy can be the difference between success and failure in a race, but I doubt you'd ever be able to perceive the change. The carbon fiber plate in the Vaporfly is fairly deep in the midsole, so there are no issues with it feeling hard under foot, which is a major downside to the [[VKTRY insoles]]insole.
* {{H:outsole}}. You can see the hard rubber outsole as the black areas on the sole of the Vaporfly. The outsole seems to be fairly hardwearing, and after some miles it's fairly grippy. It's not as good on gritty asphalt as the plastic nubs you get on Japanese racing shoes, but it's better than I expected. The outsole is placed so that most of the contact areas are protected, but there's still a lot of exposed midsole that's softer.
* {{H:shape}}. The Vaporfly shape doesn't match the human foot, so the toe box compresses the toes. I found the Vaporfly is not as bad as most running shoes, but it did give me toe blisters until I [[Shoe Dissection| cut open the toe box]]. {{H:TryCuttingShoes}}.<br/>[[File:Vaporfly Toe Box.jpg|center|thumb|300px|The toe box cut open.]]
=Other Breaking-2 Shoes=
Nike's highly publicized attempt to break the 2-hour marathon was documented in the National Geographic "breaking 2" (freely available on youtube.com). That failed attempt used the Nike Vaporfly Elite, a shoe you can't buy. This Vaporfly uses the same ZoomX foam and a carbon fiber plate in the midsole as the Vaporfly Elite. There is also the [[Nike Zoom Fly]] which looks superficially identical to the Vaporfly, but is radically different and vastly inferior.
=Is It Really Faster?=
A study [https://link.springer.com/article/10.1007/s40279-017-0811-2 "A Comparison of the Energetic Cost of Running in Marathon Racing Shoes"] looked at the performance of the similar prototype shoe to the Nike Vaporfly. This study included researchers working for Nike, as well as the University of Colorado, and it used a shoe that not actually the Vaporfly, so use caution in interpreting the study. The picture below gives some insight to the construction of the Vaporfly, but also suggests some differences from the prototype which appears to have a full with carbon fiber plate.
[[File:Nike Prototype.jpg|center|thumb|300px|The prototype Nike]]
The prototype was compared with the Nike Zoom Streak 6 (NS) and the Adidas adizero Adios BOOST 2 (AB). It's nice to see that they disclosed the actual shoes they compare it to. The researchers added small weights to the two Nike shoes so they were weight matched with the Adidas. A mechanical check showed that the prototype shoe was twice as well cushioned as either of the other shoes, deforming 11.9mm versus 6.1 and 5.9 mm. They prototype also had more bounce, returning 87.0% compared with 75.9% for the Adidas and 65.5% for the Steak. The study then compared the [[Running Economy]] of sixteen male high-level runners in the three different shoes. The runners have a [[VO2max|VO2max]] of ~72, which is translates to a marathon time of about 2:20. They tested them at 14 kph (6:53 min/mile), 16 kph (6:02 min/mile), and 18 kph (5:22 min/mile), all below the [[Lactate Threshold]] of the runners (4 mmol/l, which is good enough for this study.) The running economy of the prototype shoe was 4% better than either of the other two shoes, which had similar running economy. The study noted that the prototype shoe was slightly better for rear foot landing runners (~4.7%) than the forefoot landing (~3.6%).
=Update After 100 Miles=
Normally, I would give an update on a pair of running shoes once I'd put rather miles on them. However, the vapor fly as something of a reputation for fragility, so I wanted to track its progress carefully. Even after this short distance, there is some evidence of the foam midsole braking down. If you look at the profile picture below, you can see some increases in the midsole appearing, and there is a noticeable indent under the ball of my foot. On the underside of the shoe, there is only a small amount of abrasion on the exposed foam. The hard rubber outsole (the black areas) are completely unchanged, suggesting that they are surprisingly hard wearing. The grip has improved over the course of the 100 miles. The main abrasion area on the exposed foam midsole is on the outside rear edge, where I occasionally catch my heel on steep descents. It should be noted that my running biomechanics are fairly efficient, and I'm typically quite gentle on my shoes. The upper is doing fine, even where I've cut open the toe box.
File:Nike Vaporfly 200 Miles (3).jpg
File:Nike Vaporfly 200 Miles (4).jpg
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=Update After 300 Miles=
Another 300 miles have gone by quickly and pleasantly. The degradation of the Vaporfly has continued slowly, without any "falling off the cliff" that sometimes occurs. I've cleaned up the shoes a little more carefully for the photos below, and you can see that the midsole has a thin white plastic layer over the slightly more yellowed foam. The level of abrasion of the exposed midsole is surprisingly limited given the mileage. The black rubber outsole is even less abraded, and most of it looks entirely untouched. The midsole foam continues to collapse, but the collapse under the carbon fiber plate is far less than it would be without it. This means that the margin around the outside of the shoe where there's no plate is noticeably lower, and the area under the ball of my foot is depressed several millimeters. It's interesting when I swap back to "normal" running shoes. The extra support under the ball of the foot with fresh shoes is dramatic and feels really weird, but the big difference is how much I miss the spring of the Vaporfly.
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File:Vaporfly 300 Miles (3).jpg
File:Vaporfly 300 Miles (2).jpg
File:Vaporfly 300 Miles (6).jpg
File:Vaporfly 300 Miles (5).jpg
File:Vaporfly 300 Miles (7).jpg
File:Vaporfly 300 Miles (1).jpg
File:Vaporfly 300 Miles (4).jpg
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=A Comparison with other Recommended Shoes=
{{:Shoes-include}}