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(Pocket-lint) - Barefoot running has seemingly come and gone. But if you look closely, brands are still supporting the idea of running as close to barefoot as possible, but without all the hype.

Nike's approach is to offer three different running shoes as part of its Free range that is geared to three different running types.

The first is the Nike Free 5.0 which delivers some flexibility, but plenty of cushioning and support. The Free 4.0 Flyknit shoes take the cushioning down to a 6-millimeter offset and adds a Flyknit upper, while the Nike Free 3.0 Flyknit goes as minimal as it dares (4mm offset) without you falling through the bottom of the sole.

Determining which one you are is a fairly easy process and comes down to how much support and cushioning you are after. If it is lots then it is the 5.0 model you'll need, if it is none then you want the Free 3.0 Flyknit shoes instead.

Normally running in a pair of Nike Free 5.0 shoes, Nike asked us to do a further foot pressure test, which determined that we are a mid foot runner with strong natural support within the arch of our feet and therefore perfectly suited for the Free 4.0 Flyknit model.

Shoes fitted, we slipped a pair on and hit the road. We've run a number of times in the last three weeks since we picked up the shoes. We've worn the both as regular "day shoes" about town, and for a number of 5km+ runs.

The overriding feeling? Comfortable, but tough on the calf muscles.

As a day shoe

Around town, or as a strengthening shoe, the Nike 4.0 Flyknit offer a comfortable fit thanks to that sock-like upper. With a virtually seamless one-piece upper that conforms to the shape of a your foot, it offers a snug fit with plenty of flexibility, but only when you flex.

The Nike Free 4.0 Flyknit uses a non-stretch yarn in the heel area to add more stability and support to those who need it. Removing the structured heel counter frees up the runner's natural gait and pares down weight. In practice it works really well.

On the cushioning front, Nike seems to have got the balance right here. We've tried plenty of barefoot shoes in the past, from the likes of Merrill to Vibram to others, and the Free 4.0 Flyknit shoes merge the benefits of a training shoe with something that isn't as smothering.

The sole's design and manufacture stays the same as the 2014 range with a hexagon design to allow for maximum flexibility in all directions, and the shoe is just as flexible as before. It's very comfortable and lightweight.

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As a running shoe

Just how strong are your legs, your ankle and your foot in particular? That's the main question here as if the answer is anything other than "strong" you'll be in for a tough ride. In fairness to Nike, it is something the company did warn us about and something we experienced first hand.

After the first 5km, our calf muscles felt like they were on fire and we had a slight pain in the arch of our foot from the lack of support.

While the calf muscle fatigue has reduced the more we've run in them, anything over 5km produces the same aches in the arch of our right foot. Something we don't get running in the Nike Free 5.0 or other running shoes with more support.

Pushing these niggles aside (all feet are different) the shoe is incredibly lightweight and airy, but also subject to what's on the ground beneath you. Land on a small twig and you'll feel it, switch to grass and you can feel the small imperfections in the ground. If you like feeling the ground you are running on, these are excellent.

Of course there are downsides. All that flexibility and feeling can be tiring at first and the lack of support means you have to be wary of running cross terrain if you plan to move with speed.

The lack of cushioning also means there isn't the feeling of much spring in your stride. You have to provide the energy rather than expecting the shoe to do it for you. The Nike Free 4.0 Flyknit aren't anywhere near as "springy" as the Adidas Boost range for example.

First impressions

We've got really mixed feelings about the Nike Free 4.0 Flyknit shoes.

As a about town shoe they are brilliant, incredibly comfortable, lightweight, and cool enough to be noticed, especially if you opt to customise them via Nike ID.

But as a running shoe, we aren't sure we are strong enough to handle them. They deliver exactly what they promise, but for us, and we suspect many others, our feet and calf muscles just aren't strong enough without it causing us to ache, a lot.

Writing by Stuart Miles.