Our verdict

The KEEN WK400 makes walking sexy again! We couldn't get enough of this shoe's rocker-bottom sole which kept us going for hours on end. Its entire design encourages movement and we even found it hard to stand still. If you want to get those 10K steps done in a fun and almost effortless way, we can't think of a better option. Not to mention that it also lasts a good while and can easily transition from the city to the outdoors.

Pros

  • Rocker sole propels you forward
  • Copious amount of cushioning
  • Takes stress and pressure off the feet
  • Amazingly comfortable step-in feel
  • Highly durable and abrasion-resistant
  • More stable than it seems!
  • Can go from road to trail

Cons

  • Needs some getting used to
  • Heavier than average

Audience verdict

80
Decent!

Who should buy

In our opinion, you won't be able to get enough of the KEEN WK400 if you want:

  • a rocker-bottom walking shoe that pushes you to clock up those steps
  • a mind-blowing amount of underfoot cushioning and support
  • a durable pair with a hard-wearing outsole that can go from concrete to trail

KEEN WK400 review  

Who should NOT buy

If you find the shoe's design too exotic but want to experience the benefits of a max-cushioned, rockered shoe, we recommend the Nike Motiva as an alternative. 

Another highly cushioned, stable, and supportive alternative for all-day wear is the Hoka Clifton LS. This one has a non-rockered traditional sole shape.

KEEN WK400 lab test

Breathability

At first, the mesh upper on the KW400 looked very promising. But we quickly came to realise that all those ventilation holes on the upper don't do much for the shoe's breathability.

Just look at how little smoke is passing through this KEEN shoe's upper in our breathability test below.

Assessing its ventilation capacity on a 1-5 scale, we gave it a moderate score of 3. While it's not stuffy, we think that the WK400 feels best in moderately warm weather.

A closer look at the mesh helped us understand why the shoe lacks aeration.

KEEN WK400 Breathability microscope test

That's because the shoe's upper fabric is made of two layers! It surely detracts from the shoe's performance in hot weather but in return makes it more versatile for those transition periods between summer and winter.

KEEN WK400 Breathability microscope upper test
Test results
WK400 3
Average 2.9
Compared to 37 walking shoes
Number of shoes
1
Breathability
5

Durability

Toebox durability

KEEN is a long-standing outdoor brand that sure knows how to make durable footwear.

Thus, we were not surprised to see a barely visible yet highly protective translucent layer on the WK400. Covering the shoe's toebox, it guards the fabric from bumps and tears.

Equipped with a Dremel, we went full force drilling this sensitive part of the shoe. Maintaining consistent speed (5K RPM) and pressure (3.2N), we held the tool's sandpaper tip for 12 seconds.

KEEN WK400 Toebox durability test

And we must say, without that overlay, the KEEN WK400 would've ended up with the same glaring hole as the shoe on the right. But luckily, it earned an average score of 3 for toebox durability.

Test results
WK400 3
Average 3.2
Compared to 31 walking shoes
Number of shoes
1
Toebox durability
5

Heel padding durability

The KEEN WK400 has a humongous drop of 21.4 mm. This number is never-before-seen in our lab but so is the shoe's midsole shape.

What's the benefit of this setup? Significantly less pressure on your feet and Achilles.

When the heel is elevated above the toes, it activates a different biomechanics compared to low-drop, or flat shoes. Your own foot muscles are less activated but in return, high drop shoes give you plenty of all-day comfort and support.

Test results
WK400 2
Average 2.3
Compared to 30 walking shoes
Number of shoes
1
Heel padding durability
5

Outsole hardness

KEEN must've used its best practises from hiking shoes to make the WK400's outsole.

When we pressed our durometer against the rubber, the tool returned a high reading of 85.4 HC. This is 13% harder than the average of walking shoes and is a good indicator of durability.

KEEN WK400 Outsole hardness
Test results
WK400 85.4 HC
Average 77.6 HC
We use an average of four tests. The photo shows one of those tests.
Compared to 37 walking shoes
Number of shoes
50.1 HC
Outsole hardness
92.0 HC

Outsole durability

We've got to say, the outsole of the WK400 exceeded our expectations in the Dremel test!

Even though we had set the tool's speed to the relentless 10K RPM and held its sandpaper tip for a very long 22 seconds, the rubber refused to give in!

KEEN WK400 Outsole durability test

According to our tread gauge measurement, the dent ended up as shallow as 0.3 mm. It is nothing more than a scuff!

Test results
WK400 0.3 mm
Average 1.4 mm
Compared to 30 walking shoes
Number of shoes
0.0 mm
Outsole wear
2.0 mm

Outsole thickness

Like that wasn't enough, KEEN also used a very thick layer of rubber for the outsole.

Measuring it with a calliper, we got a whopping 5.0 mm. That's 50% thicker than the average walking shoe!

KEEN WK400 Outsole thickness

All things considered, we can guarantee that the KEEN WK400 is going to have a longer and happier life than many shoes out there. Even if you take it beyond roads and manicured paths.

KEEN WK400 lugs

Test results
WK400 5.0 mm
Average 3.0 mm
Compared to 37 walking shoes
Number of shoes
0.0 mm
Outsole thickness
7.0 mm

Weight

To afford its copious amount of cushioning and rubber outsole, the WK400 has to pay with weight.

KEEN WK400 Weight

Tipping the scale at 13.4 oz (381g) in a men's US size 9, this KEEN shoe is among the heaviest walking shoes we've tested. It is not your featherweight Skechers shoe.

But we must also point out that we didn't feel the shoe's heft thanks to its rocker-bottom design. The forward-rolling sensation it created made the heft less noticeable.

Test results
WK400 13.44 oz (381g)
Average 9.98 oz (283g)
Compared to 37 walking shoes
Number of shoes
6.17 oz (175g)
Weight
14.25 oz (404g)

Cushioning

Heel stack

Just when we think that footwear cushioning can't get any thicker, we get an ever higher-stacked shoe in our lab.

The WK400 beats our previous heel stack record of 40.0 mm with a scandalous 45.7 mm measurement!

KEEN WK400 Heel stack

The amount of cushioning and shock absorption offered by this KEEN shoe is incredible. We could walk all day without a hint of discomfort or foot fatigue!

Because of that, we can even recommend the WK400 as a recovery shoe for someone whose feet and legs get beaten up by sports and training.

Test results
WK400 45.7 mm
Average 32.1 mm
Compared to 37 walking shoes
Number of shoes
11.2 mm
Heel stack
45.7 mm

Forefoot stack

But don't worry, the shoe's forefoot feels much more down to earth.

With a calliper measurement of 24.3 mm, it is only a couple of millimetres thicker than average. It helped us get in touch with the surface beneath our feet, making the ride stable even when the terrain was bumpy and hilly.

KEEN WK400 Forefoot stack
Test results
WK400 24.3 mm
Average 21.6 mm
Compared to 37 walking shoes
Number of shoes
5.5 mm
Forefoot stack
31.2 mm

Drop

The KEEN WK400 has a humongous drop of 21.4 mm. This number is never-before-seen in our lab but so is the shoe's midsole shape.

What's the benefit of this setup? Significantly less pressure on your feet and Achilles.

When the heel is elevated above the toes, it activates a different biomechanics compared to low-drop, or flat shoes. Your own foot muscles are less activated but in return, high drop shoes give you plenty of all-day comfort and support.

KEEN WK400 Drop
Test results
WK400 21.4 mm
Average 10.5 mm
Compared to 37 walking shoes
Number of shoes
0.3 mm
Drop
21.4 mm

Midsole softness

Note: a low durometer measurement equals a soft material, whereas a high measurement means it's firm.

The WK400 also treated our feet to a comfortably soft cushioning. We could feel a sweet compression even through the stiff nylon plate.

To measure the shoe's foam softness, we pressed a durometer against its half-cut midsole. It returned a reading of 22.0 HA which is indeed on the soft side of walking shoes (15% softer than average).

KEEN WK400 Midsole softness

Aside from being plush, this foam also has a pleasant rebound. We assume that the hollows throughout the midsole play a part in that bounce.

KEEN WK400 foam hollows

Test results
WK400 22.0 HA
Average 26.1 HA
We use an average of four tests. The photo shows one of those tests.
Compared to 36 walking shoes
Number of shoes
7.8 HA
Midsole softness (soft to firm)
39.4 HA

Midsole softness in cold (%)

Note: a low durometer measurement equals a soft material, whereas a high measurement means it's firm.

Another magical aspect of this foam is that it doesn't seem to be subject to cold. If you choose to wear the shoe on a colder day, the plushness will still be there!

After keeping the WK400 in the freezer for 20 minutes, we repeated the durometer measurement and found that the foam only got 6.8% firmer!

This is impressive considering that on average walking shoe foams get 33.2% harder. 

KEEN WK400 Difference in midsole softness in cold
Test results
WK400 6.8%
Average 31.1%
Compared to 36 walking shoes
Number of shoes
0%
Midsole softness in cold
100%

Insole thickness

The comfort is further amplified by a generously padded insole. Measuring its thickness with a calliper, we got an impressive 7.5 mm which is thicker than average.

KEEN WK400 Insole thickness
Test results
WK400 7.5 mm
Average 5.8 mm
Compared to 37 walking shoes
Number of shoes
3.5 mm
Insole thickness
16.9 mm

Rocker

But the most striking feature of the KEEN WK400 is, of course, its rocker-bottom sole. Called the KEEN.CURVE, this rounded shape works as an actual rocking chair for your feet!

Even though it felt a little wonky at first, it took us minutes to get comfortable with the shoe's odd shape. But once we were there, we couldn't stop going!

This KEEN shoe brilliantly accommodated the biomechanics of walking, helping our feet roll smoothly and effortlessly through the gait cycle. It encouraged us to walk longer distances!

But be prepared that standing in the KEEN WK400 feels rather funky. You cannot really stand still in the shoe and slight rocking is the only option.

Like we said, the shoe wants you to keep going.

Stability

Lateral stability test

Just by looking at it, we would never think that the KEEN WK400 is a stable shoe. But to our great surprise, it is!

Sure, its lateral stability is not very reliable because of the rocker and we certainly don't recommend making forceful side-to-side steps in it. But if you stick to forward movements (as expected in walking), you will be treated to a very stable ride.

Torsional rigidity

The shoe comes with a very stiff full-length nylon plate that sits right beneath the insole. It made us feel more stable on our feet without losing the benefits of soft cushioning.

It also adds a great deal of torsional rigidity to the WK400. Twisting the shoe in our manual test, we rated its stiffness with the highest score of 5. 

Test results
WK400 5
Average 2.8
Compared to 37 walking shoes
Number of shoes
1
Torsional rigidity
5

Heel counter stiffness

We also felt that the shoe held our heels and ankles firmly in place, preventing inward rolling and heel slippage.

Assessing the shoe's heel counter stiffness on a 1-5 scale, we felt a lot of resistance and rated it with a high score of 4. You can expect a great deal of support not only from the shoe's midsole but also from its upper.

Test results
WK400 4
Average 2.3
Compared to 37 walking shoes
Number of shoes
1
Heel counter stiffness
5

Midsole width - forefoot

To make the WK400 as stable as it can be, KEEN granted it one of the widest platforms we've seen in walking shoes.

Measuring the widest part of the shoe's midsole in the forefoot, our calliper showed 115.5 mm. That's a few millimetres wider than average.

KEEN WK400 Midsole width in the forefoot
Test results
WK400 115.5 mm
Average 111.9 mm
Compared to 37 walking shoes
Number of shoes
98.8 mm
Midsole width - forefoot
124.1 mm

Midsole width - heel

If the shoe's rockered sole still makes you feel unsure about stability, take a look at the width of its heel!

With 97.0 mm in the widest part, it is among the widest platforms you can find in walking shoes.

KEEN WK400 Midsole width in the heel
Test results
WK400 97.0 mm
Average 90.3 mm
Compared to 37 walking shoes
Number of shoes
75.6 mm
Midsole width - heel
104.0 mm

Flexibility

Stiffness

The stiff plate we mentioned earlier is an essential component of the shoe's rockered design. It helps to maintain the sole's curved shape as our feet roll from heels to toes.

KEEN WK400 flexibility

To measure the level of stiffness in this KEEN shoe, we bent it to a 90-degree angle using a force gauge. The tool showed that it took as much as 32.8N to do that. That's 60% more than it takes an average walking shoe!

Test results
WK400 32.8N
Average 20.3N
We use an average of four tests. The video shows one of those tests.
Compared to 37 walking shoes
Number of shoes
1.1N
Stiffness
52.7N

Grip / Traction

Most walking shoes trade rubber outsoles for exposed foam to keep the weight down. That often leads to compromises in durability and grip.

KEEN WK400 outsole

But the KEEN WK400 turns that around with a sturdy and lugged outsole. Having wear-tested the shoe on various surfaces (from concrete to singletrack), we can confirm that it is indeed an all-terrain type of shoe.

It is not a dedicated off-road shoe by any means but it can handle light-to-moderate trails well. 

Size and fit

Toebox width - widest part

What the brand calls a "Contoured Fit," we refer to as a normal medium-width fit. We haven't experienced any discomfort or issues with the fit.

KEEN WK400 fit

Measuring the shoe's toebox in the widest area, our calliper showed 100.5 mm. This is on par with the other walking shoes we've tested in a men's US 9.

KEEN WK400 Toebox width at the widest part
Test results
WK400 100.5 mm
Average 99.2 mm
Compared to 37 walking shoes
Number of shoes
89.5 mm
Toebox width - widest part
110.9 mm

Toebox width - big toe

Repeating the calliper measurement near the big toe, we got 75.4 mm. This indicates a slight tapering but nothing critical for a medium-width foot.

KEEN WK400 Toebox width at the big toe
Test results
WK400 75.4 mm
Average 78.6 mm
Compared to 32 walking shoes
Number of shoes
73.7 mm
Toebox width - big toe
94.3 mm

Tongue: gusset type

The tongue of the WK400 is partially attached to the upper on both sides.

This creates a more secure midfoot hold while also preventing the tongue from bunching and sliding.

KEEN WK400 Tongue: gusset type
Test results
WK400 Both sides (semi)

Offset lacing

You might as well be surprised by the shoe's offset lacing design.

KEEN WK400 asymmetrical lacing

Like the rest of this KEEN shoe, it felt alien at first but we got used to it within the first hour. Although we cannot pinpoint any outstanding benefits of this setup, it didn't cause any pressure points either.

Comfort

Tongue padding

The interiors of the WK400 are lavishly padded in both the tongue and the collar.

Measuring the tongue thickness with a calliper, we got 9.0 mm which is a few good millimetres thicker than average.

KEEN WK400 Tongue padding

Combined with the shoe's thick insole and cushy midsole, this KEEN shoe provides an exceptionally cosy step-in feel.

Test results
WK400 9.0 mm
Average 5.2 mm
Compared to 37 walking shoes
Number of shoes
0.3 mm
Tongue padding
13.4 mm

Heel tab

A small but thoughtful detail is the shoe's two-finger webbing loop. It is an unusual design that comes super handy when getting the shoe on.

KEEN WK400 Heel tab
Test results
WK400 Finger loop

Removable insole

There is an option to replace the shoe's stock insole with your own. But we don't think it would be necessary given its extra plush padding and contoured shape.

KEEN WK400 Removable insole
Test results
WK400 Yes

Misc

Reflective elements

Better be home before dark! This KEEN shoe doesn't have any reflective elements to make you visible in low-light conditions.

KEEN WK400 Reflective elements
Test results
WK400 No