The Karhu Flow Trail turned out to be a bit of a mixed bag. One the one hand, the low forefoot, low heel-to-toe drop, stable platform, and form-fitting upper (for some testers) make for excellent handling on technical terrain. On the other hand, the midsole is not very responsive, so while the shoe handles well, faster running is somewhat inhibited.

The shoe also is in an awkward weight range where it is a bit too heavy to provide true trail flat performance (it felt heavier than its 9.0 ounce weight suggests), but not cushioned enough to make a viable long distance shoe. One other concern is a significant amount of exposed midsole material, which reduces push-through protection from rocks and also likely affects durability.

Despite these drawbacks the Flow Trail is a reasonable daily trainer for groomed trails and other more forgiving surfaces. Most mid-pack runners would probably find it adequate for up to marathon distance racing, but might want something more durable and protective for longer distances. Competitive runners would want the opposite, i.e. something lighter and more responsive. Runners who like a flexible platform and lots of ground feel, but want just a touch more protection than minimalist offerings, might like this shoe a lot.

Comfort and Protection

Overall the Flow Trail is a comfortable shoe. The upper material is soft to the touch and feels very supportive. Underfoot the cushioning is not plush by any means but it does have some softness and pliability. The protection underfoot however is quite poor, and several testers reported that they could feel rocks and other trail debris pushing through. A rubberized rand that runs all the way around the shoe does provide some protection against kicked objects and other glancing impacts. However, without a full length outsole, it seems a little out of place. The toe box also is somewhat narrow, which could lead to discomfort and/or blistering on longer runs.

Security of Fit

Security of fit seemed was variable among testers. Because the upper lacks overlays, foot security really comes down to how well the upper conforms to a runner’s individual foot. At one extreme, some found the upper to be loose and sloshy. At the other extreme, some found the upper to be extremely form-fitting

The upper of the Flow Trail is very form-fitting and that really helps keep the foot in place without excessive lace pressure. The result is that the laces are just there to help wrap and secure the upper material around the foot, and don’t themselves have to provide any sort of stabilizing function. The foot bed also provided a good fit, which helped to minimize interior movement. Lastly the low forefoot height helps to stabilize the entire shoe by reducing the potential for rotation and torque during hard aggressive foot placement.

Speed & Energy Efficiency

The Flow Trail has fairly good turnover due to the low-profile ride and the moderate heel-to-toe drop, and the shoe felt smooth as the pace was increased. The weight is somewhat too high to provide racing flat performance, but at least is well balanced and doesn’t feel awkward during faster running. On the other hand, the lack of underfoot protection demands more careful placement if any trail hazards are present. So even though the shoe does run fairly well, the reality is that there is a limited range of terrain on which this can be taken advantage of.

The lack of response in the midsole was probably the most disappointing characteristic of the Flow Trail and made the shoe feel more labored than it should have during periods of faster running. The shoe also felt inefficient on climbs that were steep enough to force primarily forefoot running with little to no rear- and mid-foot ground contact.

Agility

The Flow Trail felt very nimble on technical surfaces, but was somewhat hampered by the lack of torsional stability and marginal forefoot traction. So while precise foot placement was easy to achieve, both confidence and control were reduced. The shoe also struggled on steep technical descents for these same reasons.

Value

The retail price of $120 is about average.