Keen Ridge Flex Waterproof Hiking Boots. Photo: Bob Smith/grough

Price: £155
Weight: 1,179g/pair
Construction: leather/mesh uppers
Country of manufacture: Thailand
Waterproofing: Keen.Dry
Sole stiffness: 4/10
Women’s version: yes
Sizes: men’s 6-16; women’s 2½-9

The Ridge Flex is a lightweight walking boot that uses a combination of leather and synthetic mesh in its uppers.

Its innovative and unique (as far as I know) feature is the Keen Bellows Flex section at the base of the laced part of the boot, which is a rubberised area linking the forefoot with the ankle section of the boot, at the point where it flexes during walking. There’s also a narrow bellows strip at the base of the ankle cuff.

This flex area is the main point of movement in a boot and can sometimes cause discomfort if the upper is pressed into the forefoot during the natural walking movement. It also has the potential to crack over time due to the continuous compression and expansion at this location. Keen has tackled the problem by using a fairly soft rubber insert with four ridges between the leather of the toe section and the bottom lace anchor.

The ankle cuff is comfortable and also has a small rubberised inlay. Photo: Bob Smith/grough

The brand says this arrangement cuts the amount of energy needed to bend the foot here by 60 per cent, enabling an easier feeling walk. The effort used in flexing a boot while walking is not something I would normally have considered, but having put a few miles in while wearing the Keen footwear, it does actually feel less effort, though that could just be a case of autosuggestion, of course.

The boots are fairly light too, which helps reduce fatigue. The leather sections of the uppers are quite pliable and are supplemented by tough-feeling plastic areas around the heel and lower forefoot sections. There’s also a rubberised area at the toe box to help protect against knocks. A heel-lock system uses a webbing strip running from the laces through the heel plastic and then wrapping over the top of the heel cup. This worked well and there was no heel lift while walking uphill.

The forefoot is wide and felt quite roomy. Volume is average. This suited my feet, but they may be less suitable if you have a narrow forefoot. As with all footwear, it’s best to try for fit before you buy.

The ankle cuff is made from fabric and is well padded, providing good comfort.

Underfoot cushioning is good too, thanks to both a moulded EVA midsole and an insole with a generous helping of foam, particularly at the heel.

The boot has Keen’s own Keen.Dry waterproof membrane which, when combined with the leather and plastic uppers, kept the rain, snow and water out during testing. The tongue gusset, however, only extends part way up the boot, so there’s potential for water to get in there if you’re passing through deep puddles or snow.

The outsole provided good grip. Photo: Bob Smith/grough

The lacing uses Keen’s Speed Lace system, which allows the laces to pass freely through the three bottom pairs of webbing loops before locking them in the top two pairs of metal hooks. The laces are quite short so there isn’t much to play with when knotting them, but if the forefoot laces are tightened sufficiently, it wasn’t a problem.

There was some initial discomfort in the instep area when the laces were tightened. Slight loosening helped and eventually this discomfort disappeared.

The outsole is Keen’s own, with 5mm-deep lugs and a fairly soft rubber providing good grip. Traction on rock, grass, gravel paths and stone flags was very good and braking was good too.

The membrane, combined with the leather in the uppers made the Ridge Flex Mid WPs feel quite warm, which was welcome on cool and cold days but less so on longer days when the temperature rose.

Overall, the Keen boots were comfortable, with welcome underfoot cushioning and a roomy forefoot. The uppers were pliable, while still offering support.

The Bellows Flex in action. Photo: Bob Smith/grough

The big question is: did the Keen Bellows Flex system cut the amount of energy I needed to stride out? I think it’s impossible to say with any certainty how much the bellows cut the amount of effort needed, but it did feel like a good gait came more easily and I can see a definite long-term benefit, both from this and the likelihood the rubber section will be more durable and resistant to cracking than, say, a leather boot with conventional uppers in this area.

Keen says the boots have ‘million flex goodness’, which I calculate equates to about 1,500km or 932 miles, which will get you from John O’Groats to Land’s End, with a bit to spare.

There was certainly no digging in of the flex point to the foot, which has been a problem with some boots in the past.

The leather in the boots is from a Leather Working Group ethical source, and the durable water repellent treatment is PFC free. The Keen Ridge Flex also have a natural eco odour-control treatment.

I used the Keen Ridge Flex boots extensively in conditions ranging from wintry days to warm, dry weather, fellwalking to moorland and trail outings. After initial pressure points in the instep, lacing adjustment to find the correct tension removed this and the boots were very comfortable.

The Keen Ridge Flex Waterproof boots were rated a good buy. Photo: Bob Smith/grough

They are ideal for the UK countryside and even on less demanding fellwalking routes. The soles are very flexible, so don’t give the kind of stability needed on rock ridges or technical terrain but for typical hill trails and country paths they worked well. I’m still not convinced the rubber bellows allow, as Keen says: ‘3x easier days on the trail’, but after numerous days on the hoof, the system certainly stops any cutting into the foot at the flex point and walking in the boots was easy.

Best uses: UK trail walking, hill trail walking, countryside walks, multi-day walks, trekking, non-technical mountain routes.

Performance 34/40
Comfort 27/30
Versatility 7/10
Quality 7/10
Value for money 7/10
Total score: 82/100

The Keen Ridge Flex boots were supplied to grough by Keen.