Nike Free Flyknit 4.0

The Nike Flyknit 4.0 is the newest upgrade to the Flyknit series. Coming from the brand's Free line, these offer a minimalistic style which is aimed at those who like the lighter, lower profiled running shoes. The version was originally released with enormous success and remains a quite popular choice for both, casual and athletic applications. This updated version offers many fixes to past criticism that Nike received regarding the Flyknit 3.0. One such issue was with the size of the previous version's tongue. Another was about the shoe's width. The 4.0 offers more flexibility, breathability and also adds to the already unique overall design.

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Where to Buy
Road Runner Sports Link
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Where to Buy
Road Runner Sports Link
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Pros & Cons
  • Stylish designs, offering more than 30 coloring schemes
  • Great breathability and flexibility, using unique Flywire woven technology
  • Comfortable design, and very responsive
  • Designed to promote efficient strides
  • Cons
    • Shoe runs more narrow, which may be problematic for some
    • Slightly less durability than heavier shoes
    • Not the most protective shoes against rough terrains.
    • Key Features
      The Flyknit 4.0’s outsole, or the bottom of the outside, is very flexible, rather than rigid, to deliver a more minimal running experience. This flexibility stems from its unique hexagonal design, and secondary outsole. The outsole also reportedly features rubber in higher impact areas to prevent wear and tear, though it is still relatively thin compared to other outsoles.
      The midsole is the layer located between the outsole and the upper and has the very important role of cushioning and stabilizing during impact. The Nike Free Flyknit has a midsole made up of phylite, which is a material composed of 60 percent phylon and 40 percent rubber. This is designed to absorb shock and improve the responsiveness. The midsole is fairly low, in order to fit with the minimalistic style, and also promote efficiency in stride.
      The upper of the Free Flyknits holds the foot in place from the top, while also protecting from dirt and rocks. The upper is a one-piece construction, and woven using Nike’s Flywire technology, which is done to create a seamless feeling and make the shoe more glove-like in response to a runner’s feet. This unique design also helps in adding support to the midfoot. The tongue, which is the part where the laces rest, is a traditional tongue, as opposed to the 3.0s more narrow tongue which was a source of complaint.
      The Nike Flyknits are an extremely light pair of shoes, weighing 7.6 oz for men’s size 9, and 6.3 oz for a size 8 in women's. This is significantly lighter than most trainers on the market and is designed to simulate minimalism and mimic barefoot running. The weight is very significant in determining stride and can, therefore, make a real difference in running speed. Heavier shoes provide more cushion and stability but also are a bit slower. While the difference may seem negligible, over the course of a longer race, heavier shoes can lower times by a matter of minutes. With the Flyknits, the weight is a sweet spot that promotes a more efficient stride, while also not being too light, which could cause injury.
      Breathability refers to a shoes' ventilation and ability to prevent humidity and sweat within. These have a unique breathability design, with ventilation knit into the upper. The result is a well-ventilated shoe, perfect for those looking for a glovelike fit to their running shoes. This design is also important in preventing sweaty cramped feet, sores, or blisters, which no runner enjoys.
      Comfort matters when purchasing shoes, as a runner must consider the idea of running in these shoes for mile upon mile upon mile. For those who prefer a glove-like, second skin feel for their footwear, the Flyknits are a perfect fit. With a flexible outsole, and upper, as well as lightweight design, the Flyknits offer a very comfortable fit, which would help minimize blisters and other distracting discomforts while running. In terms of fit, the Flyknits should not need to be downsized or upsized as well and offer a good fit for a runner’s usual size. It is important to note that the shoe is slightly more narrow at the front than most running shoes, however, which may be an issue for those with feet that run a bit wider .
      Nike once again offers a lot of styling options and colors for the Free Flyknit 4.0s. Boasting over 30 different vibrant color options and laces, for both men and women, runners are sure to find a style that suits them with these shoes. Whether it be the eye-catching Bright Crimson and White, or standard Black and Blue, or anything in between, there is a style for almost everyone. The Flyknits also even offer more casual color schemes, in dark colors like black and grey, making non-running everyday use a possibility as well.
      Durability should also be an important factor to consider when purchasing shoes, as most don't really want to spend money over and over again because the product doesn't last as long as it should. The Flyknits are somewhat less rugged than the average pair of trainers due to their lightweight styling. Nike has taken steps to minimize this, like the previously mentioned extra rubber on high impact areas, but these shoes will still wear out a little bit faster than a heavier of running shoes. That being said, many runners are used to replacing their running shoes somewhat frequently, so it really comes down to personal preference here.
      With a flexible design, the Free Flyknits provide great protection for your feet while running, aiding in injury prevention. The biggest thing to watch out here is the model's lightweight nature, which could be problematic with hard impacts, like when stepping on larger rocks for example. If you are careful and avoid these, the Flyknits should offer enough protection for your feet from most issues.
      Responsiveness describes the response experienced each time it impacts the ground. The Free Flyknit 4.0s offer great responsiveness, thanks to the shoe's phyllite midsole and flexible outsole designs. This creates a very responsive step when pushing off, arguably on par with minimal or barefoot running. The Flyknits are certainly top notch when it comes to the responsiveness of strike.
      The Flyknit provides a bit less support than you would find in a more traditional running shoe as a result of its design and orientation towards minimalistic running. It provides enough support to separate it from pure barefoot running, while still maintaining it’s lightweight, and a glove-like feel. It hits a sweet spot that allows runners to experience this minimal style of running while still protecting from all of the injuries that commonly occur with it.
      Being lighter styled shoes, the Flyknits are more oriented towards less punishing terrain. Grass, asphalt, and concrete are all optimal, while more harsh terrain such as rocky cliffs, or trails might be more problematic, especially for longer runs. For shorter distances though, the Flyknits are fairly versatile for most terrains. With the woven breathability slots, they need to be usable in wetter or more rainy conditions as well.
      The Flyknits had initially debuted at a somewhat expensive price, but today the pricing on this model is actually quite reasonable. They can be found at most retailers around the same general price range, which is that of an average running shoe. Compared to the standard pair of running shoes, the Flyknits hit the target right on, but also provide good value for their cost.
      Traction of running shoes refers to the grip of them on various surfaces. The traction on these shoes is somewhat limited in comparison to traditional running shoes. This again can be attributed to its minimalistic design and the material and thickness of the outsole. For use on concrete, asphalt, or track, this traction is certainly sufficient, but on another terrain, it may be a little challenging.
      Flexibility also is pretty important in allowing the feet to function with a more natural range of movement. The Flyknits are extremely flexible, in order to simulate the bare mechanics of running. The upper is woven with Nike’s Flywire technology, allowing it to flex and bend naturally with the foot, almost like a sock. The midsole complements this by being extremely flexible as well, creating a comfortably pliable shoe.
      The thinner outsole comes into play here, making them slightly less stable than most trainers. The outer layers of rubber designed to protect impact are small, and not always sufficient for all types of runners. This in tandem with the less gripping outsole, makes this shoe a bit less stable. That isn’t to say that they are an unstable pair of shoes, however. The Flyknits are certainly stable enough for extended running, but it is just important to point out that minimalist styled shoes will be a bit less stable than traditionally styled running shoes.
      The drop, or measurement of the heel size of a shoe, on the Flyknits is 6mm long, which is slightly bigger than expected for a minimalistic shoe. It is a bit counterintuitive for barefoot-style running, though does not provide a huge disruption from the overall feel.
      Key Features
      •Nike Flywire design providing great flexibility of the upper

      •Hexagonal midsole to allow for wide range of movement

      •Lightweight design, weighing in at less than 7 oz

      • Ventilation woven into upper, for great breathability

      •Comfortable design, and well suited for minimalist styled running

      •Great variety in color and laces

      •Ability to be worn as an everyday shoe
      Bottom Line
      Nike's Free Flyknit 4.0s are a great pair of running shoes for those seeking a lighter option. The breathable and lightweight nature of this shoe makes it a great choice for many, and the vivid array of colors allow for customization and personal style as well. The weight also hits a sweet spot for optimizing stride and speed while also providing protection. The only drawbacks of the Flyknits are their slightly reduced durability and stability, which are understandable, considering the nature of minimalist and barefoot style shoes. These shoes are a great value for any runner who is looking for a stylish pair of lightweight and barefoot styled trainers, but also for anyone who is seeking stylish shoes for day to day activities or for general fitness.
      Where to Buy
      Road Runner Sports Link
      See Deal
      By Abbie Copeland
      Last updated:
      Where to buy
      Best offer on: Jul. 29. 2021

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