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Vibram FiveFingers KSO Review

Posted Aug 27 2009 10:30pm
(Admin note: this is the second of a two-part review of Vibram FiveFingers footwear. If for some reason you missed my very glowing, but admittedly long-winded introduction to the product line, check it out here.)

Among the four versions of FiveFingers currently offered by Vibram, the KSO has become the model of choice among runners seeking the biomechanical, musculoskeletal, and psychological (yes, really) benefits of barefoot running without fear of the various hazards that keep most of us grounded in traditional shoes.

One key to the success of the FiveFingers (often referred to as “VFFs”, or sometimes “Fives”) line – in addition to everything I mentioned in the previous post – is that Vibram does a remarkable job of welcoming customer feedback and incorporating it into updated versions of their product. When early adopters began running in the FiveFingers, they reported that the upper didn’t always feel secure; that led to the strap feature found on the Sprint. When trail runners reported that dirt sometimes slipped into the shoe, Vibram added a thin mesh layer underneath the strap which became the KSO.

(And when KSO users reported that the KSO wasn’t warm enough for extremely cold conditions, Vibram created the Flow – but that doesn’t really pertain to this review. I’ll try to stay focused on just one model from this point on, I promise.)

VFFs are also called "gorilla feet" by users ... for obvious reasons

From a spec standpoint, here’s what you get with the KSO: the upper combines a thin, abrasion-resistant stretch nylon and breathable mesh upper that wraps your forefoot to "Keep Stuff Out." A hook and loop closure sits comfortably above the mesh and helps secure the fit. Underneath, a non-marking 3.5mm performance rubber Vibram outsole is razor-siped for traction – more on that in a bit. The outsole material actually extends around the front of the foot, which is a very cool design feature for improved scuff protection to the tips of your toes. There is a 2mm EVA midsole to provide just a touch of comfort without diminishing the barefoot feel. The entire shoe weighs 5.7oz, which barely seems like anything at all when you’re on the run.

VFFs don't Keep all Stuff Out; your feet will still get dirty through the mesh

The main caveat for first-time users to beware of with FiveFingers is in the sizing. Vibram uses European sizing, but since this is a form-fitting garment, you can’t make a straight conversion from your US shoe size to pick the VFF equivalent. You actually need to measure your foot, and match your foot length with the size chart on Vibram’s website. If you purchase FiveFingers from a store, the salesperson should have a specific Vibram foot ruler to determine your proper size.

My primary aim was to wear the KSOs on trails as much as possible, for a couple of reasons:

1) Although I’m improving my pain tolerance and increasing my duration of barefoot running time on asphalt roads, I still find running trails barefoot to be quite painful. I’m not nearly up to dealing with jagged rocks and knotted roots and pesky thorns quite yet – and whenever I do venture that way, it’s at an absolute snail’s pace.

2) I’m pretty sure I’ve mentioned this once or twice before … but I love trail running. That’s my thing. If being a barefoot runner means I can’t enjoy the trails, I’m having no part of it. Also, given my background in ultras, I’m curious as to whether the VFFs might be a viable option for running super-long distances over the rugged terrain I’m accustomed to seeking out someday.

(And before someone points it out: yes, I’m aware that the super-guru of the barefoot running community just ran the Leadville 100 in VFFs. But he’s Barefoot Ted, and I’m Idiot Donald. There’s a difference.)

So that’s exactly what I started doing. I wore the KSOs on all of my normal trail routes: over big climbs, narrow single track, loose rocks, steep canyons, and brush-covered hillsides. With a few exceptions, the FiveFingers handled all of these conditions quite well.

High above the Salinas Valley; you can barely tell that there's anything on my feet

It only takes a few strides to realize that you have to change your running form while wearing the VFFs; without any cushioning, your heels will get sore in a hurry if you insist on using the same heel striking gait that you do while wearing shoes. Coincidentally, heel pain is one of the most common complaints from beginners wearing FiveFingers.

(For this reason, and several others, many barefoot experts recommend that you don’t try VFFs until you’ve practiced pure barefoot running for a while; having a completely naked foot forces you to use proper form immediately, while VFFs allow you to “cheat” a bit, which could lead to injury.)

Although the outsole provides protection from the trail, you’re still able to feel every bump and contour of the ground underneath your feet. You can tell the size and shape of pebbles you step on, note the relative softness of various types of mud, and feel the change in texture from dirt to leaves to wood chips or anything else you encounter. You can even feel temperature changes from shady areas to exposed sections of trail. Perhaps this new sensory input becomes diminished over a long period of time (it’s a normal accommodation mechanism of your central nervous system, like the way you don’t notice a clock ticking in the background after a while) but I kind of hope that it doesn’t: it’s a very cool awareness that makes you feel more connected to the Earth somehow.

The VFFs are blurry, but the view is great; that dark sliver of land way off in the distance is the Monterey Peninsula stretching into the bay (click to enlarge)

The altered biomechanics and lack of cushioning will definitely slow you down a bit, but not nearly to the degree that running barefoot does. Theoretically, since your feet are lighter than when you’re wearing traditional shoes, you should be able to run faster than usual, but this is definitely a long-term adaptation. After several weeks of using VFFs, I’m able to climb steep hills almost as fast as I can in shoes; on level ground, I’m probably 30-60 seconds per mile slower than normal. It’s on the downhills that I’m still quite slow, attributable to two factors.

Wearing normal footwear, it’s on the down slopes that people place the most impact through their heels – therefore, it’s these sections where the lack of cushioning is most noticeable with the FiveFingers. It requires some major adjustments (and constant reminders) to shift your weight forward and use a midfoot strike on long downhill stretches of trail. I’m normally someone who likes to go “bombs away” down steep hills, so this is an especially challenging change for me to make.

The other limiter on my downhill speed is the traction - or lack thereof - of the outsole. For 90% of my running, the grip is fine, but I’ve noticed that on steep descents - especially if there are loose rocks or gravel to contend with - I experience a lot of slipping from the VFF. Since my standard trail shoes are La Sportivas, whose sticky rubber and angled lugs set the gold standard for traction, the difference is even more noticeable when I wear FiveFingers. It’s probably equivalent to wearing a road running shoe on technical trails: most of the time you can get away with it, but in some situations, you might find yourself in trouble.

Going down this hill was pretty sketchy

(Remember how I said that Vibram applies customer feedback so effectively? The traction issue is supposedly going to be addressed with the upcoming Trek model, designed specifically for trail running with a more grooved outsole and more durable upper. Needless to say, I’ll be VERY interested to check that one out someday.)

The only other drawback worth mentioning is kind of an odd one: many people report that the VFFs stink a lot. Since you don’t wear socks with the VFFs, and since most users don’t rotate pairs like people do with traditional running shoes, the funk potential is pretty high. FiveFingers are built with an antimicrobial footbed, and they are machine washable (but not dryer safe; they need to be air-dried) - but these are people’s feet we’re talking about, so I imagine that the situation could get kind of nasty. I haven’t experienced this phenomenon with my VFF yet, but perhaps I just haven’t used them enough.

I need to work on this pose, or come up with a new one. Is it normal to be unable to raise one foot higher than the other knee?

Honestly though, if a little bit of stink is enough to deter you away from FiveFingers, I feel badly for you. This really is a wonderful product to own, with large benefits for both traditional footwear users and the dedicated barefoot (or “minimalist”) crowd. You need to start slowly, and you need to build up your use of FiveFingers gradually to let your legs and feet adapt to the different demands placed upon them – but once you get to that point, they could provide you with some of the most uniquely enjoyable experiences you’ll ever experience in running.

The FiveFingers KSO retails for $85 on the Vibram website. A Google search will turn up a few sites offering them for $75-80, but these generally have limited selection of size and color. (And for some unfathomable reason,, who discounts everything, sells them for $109. Normally I recommend Amazon, but in this case, stay away.) The black model is sold (and well stocked) at, which may be more convenient for exchanges if necessary.

If you have any interest at all in the barefoot movement, you owe it to yourself to try Vibram's FiveFingers. It could potentially change everything you know and feel about running.

See other product reviews on sidebar at right. If you have a product you’d like reviewed, contact me
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