The Boreal Mutant was the best fitting shoe for my “duck foot;” narrow heel, wide forefoot, but low in volume overall. The Zenith rubber was surprisingly effective, the sensitivity was high, and toe/heel hooking ability was excellent. The shoe feels like a modified slipper, sensitive and flexible, but with a touch of added edging prowess. These characteristics, combined with the fit, made these a regular choice for local limestone sport climbing and bouldering areas when the agenda was unknown; these shoes could do everything well in such areas, with the fit and comfort a huge bonus.
The Boreal Mutant is essentially a slipper with a Velcro strap, but it does have a midsole and a moderately stiff rubber compound, so it edges better than a classic slipper. The Zenith rubber provided good traction for edging on crimpers and felt particularly sticky edging on plastic holds. If the route or boulder problem was overhanging and the edges were positive, we found the sensitivity and stiffness to create moderate edging ability. On vertical terrain with tiny or less than positive features, the shoe displayed some of its slipper characteristics by rolling. Not quite a classic slipper, but not quite an edging specialist—it’s, a middle of the road contender more suited to edging on overhanging routes and boulders.
The Mutant’s sensitivity was excellent, second only to the Scarpa Drago. There is a midsole, and the Zenith rubber is on the thicker side for a sport/bouldering oriented shoe (4mm-4.5mm, depending on size) so there is some loss of sensitivity compared to a slipper without a midsole and thinner rubber. Smearing on smaller features and pulling against minor protrusions transmitted ample information, but the Zenith rubber lacked adhesion on glassier surfaces compared to some of the other rubber compounds.
The Boreal Mutant is one of the best toe and heel hooking shoes in the test. Boreal mixed bits of Zenith rubber with an adhesive and painted this mixture about halfway up the upper of the shoe. This gives less traction than Zenith rubber alone but allows the upper to remain flexible, allowing good conformity and feel while aggressively toe hooking. The closure strap is very high on the shoe as well, keeping it out of the way when precise toe hooking feel is required. The heel hooking of the Mutant was second to none. The heel of this shoe fit my narrow heel better than any other, and combined with 100% rubber coverage and high sensitivity; the Mutant assisted in the most confident heel hooking of the test category.
The Mutant proved to be adequate in pocket climbing; the toe box shape is a little more rounded than others so utilizing smaller pockets could be more challenging than more pointy options. The middle of the road edging ability and high sensitivity did inspire confidence when weighting pockets on slightly overhanging routes. The downturn of the shoes greatly diminished with use, making pulling on smaller pockets on steeper routes and boulders more challenging as the shoes aged. Similar to the edging performance criteria, the Boreal Mutant sat firmly in the middle of the road for pocket climbing.
The Mutant was one of the better crack climbing shoes of the test category. The slight amount of stiffness and Boreal’s Friction Skin coating on the upper aided comfort and stickiness of foot jams and the high closure strap stayed out of the way for all but placements that swallowed the entire shoe to the ankle. The very front of the toe box has a thin vertical profile, but quickly increases with a prominent bump out for the big toe knuckle; toe jamming works well, but only if this feature fits in the crack. For foot jams, this bump out wasn’t an issue. Again, for a sport climbing and bouldering shoe, the Mutant had some decent crack climbing chops.
The Boreal Mutant accommodated my narrow heel, wide forefoot but low volume feet better than any other model in the test category; the overall shape, volume, and moderate asymmetry created a second skin feeling almost everywhere. The heel’s fit was spot on, no other shoe in this test segment could come close to matching the fit in this area. The width of the shoe at the forefoot was appreciated and was one of the few that felt supportive all the way out to the little toe, instead of feeling like that side of the foot was hanging over the edge of the outsole. The arch area of the shoe felt high and combined with the Lateral Torsion System (a thicker rubber section of the outsole under the arch) and the closure strap, provided outstanding support for the midsection of the foot. The elastic on the upper of the shoe extends very high, making getting into the Mutant a challenge but creating a very secure fit and feeling; the strap felt unnecessary much of the time. The toe box has a prominent bump out for the knuckle of the big toe; this bump out and the Friction Skin coating created noticeable ripples in the upper of the toe box that was present even while turning the foot down while ascending steeper rock. We ordered half a size down from street shoes, and the unlined upper stretched that half size. The Mutant continued to improve in comfort each time we used the shoe, but the downturn dissipated to an almost flat profile.