Hands-on review: Keen WK400 walking shoes

This isn’t the first time that footwear designers have come up with curved soles. Some shoes are intentionally wobbly to keep your muscles active. Others, like these, have a ‘rocker bottom’ so that the act of walking propels you forwards, from one step to the next.

Rather than just aping others, Keen has designed the WK400 walking shoe from scratch. Three years, nearly 10,000 hours of design and development, and 5,000 miles of testing contributed to its all-new KEEN.CURVE geometry, with a 3D plate and curved sole.

The full-length plate maintains the shape of the curve and reduces energy loss, while using a high-energy, bouncy EVA midsole. That EVA compound is lightweight and returns energy into your step. The last has a 10mm drop, which is high compared with the trainers that most walkers wear. This is designed to propel you forwards, giving a sense of forward momentum without making you rock backwards. Meanwhile a super-sized 31mm of toe spring – compared with an industry standard 20-25mm – gives an exceptionally smooth, easy transition from heel to toe off. It literally puts a spring in your step.

Finally, the outsole has a clever design. It’s wide for stability, made from a rubber compound that’s grippy on a wide range of surfaces, and has cut-outs to reduce weight. It feels light. I tested a size EU 39 and each shoe weighed just 305g.

I tested it in bright yellow but it’s available in six colours. I was frankly daunted at the prospect of the curved sole. I thought I’d teeter and fall over. In photos, it looks like a balance board of a shoe.

But there was no falling over, despite my legendary clumsiness. The result of all that clever sole design is a rolling feeling, dynamic and springy. I felt like Tigger. The shoe is lightweight and has superb grip that’s effective whether you’re on or off road. While the rest of the sole gives a really bouncy feeling.

Even without the curve, it feels energising, the high-energy midsole propelling you into the next step. The curve adds a sense of forward momentum but it’s not one that feels like you’re off balance. You don’t notice the curve much, you just feel energised, one bouncy step at a time.

The only time I did notice the curve was at the top of escalators, where the curve made me feel a bit more vertiginous than normal. It felt like gravity wanted to pull me into running down the steps.

The springy but stiff sole is the star of the show (star of the shoe?) but the upper also plays its part. It’s a very lightweight, breathable mesh. The asymmetric laces are towards the outside of each shoe. The offset lacing apparently reduces pressure on the top of your foot.

There’s a double heel loop, so you can use two fingers to ease the shoe on. That’s good, but they’re each only just big enough for a slim finger. I prefer a single loop that’s big enough for two fingers – some shoes have a larger loop like that but horizontally, not vertically. But that’s my only criticism. I was impressed with the shoe’s comfort and performance. I was even impressed with the way it stayed beautiful and yellow, without picking up much dirt.

The Keen WK400 is a good-looking trainer. I personally liked the bright yellow a lot but there are subtler colours too. And it lives up to its promise to make walking a breeze, with a real sense of forward momentum thanks to the curved sole that leads from every step to the next. I walked more when I was wearing them. With apologies for the earworm, it felt like I was walking on sunshine.

£135 keenfootwear.com

Alternatives

MBT Sport 4

A breathable mesh and synthetic suede upper, PU insole for shock absorption, high-rebound compressed EVA midsole for efficiency and comfort. The materials and curved sole don’t just promote walking, they improve posture, balance, muscle tone and even enhance muscle activation to reduce back pain.

£219 mbt.com

New Balance Fresh Foam X More v4

NB rocker-bottom shoes with more of its Fresh Foam than ever, for a stable-yet-plush feel. The outsole combines cushioning and flex for a natural stride, while the rocker profile promotes a smooth transition and ride. The trainer-style design in a range of colours looks great too.

£140 newbalance.co.uk

Summit Vectiv Pro Trail Running Shoes

Vectiv shoes all have a 3D plate and rocker midsole with lots of cushioning to give forward momentum. The range includes shoes for running, hiking and more. This one combines Vectiv tech with grip and breathability for running in the wild.

£225 thenorthface.co.uk