Shoe Review: Karhu Fusion Ortix

Two runners wearing the Karhu Fusion running shoes before a track workout

The new Karhu Fusion Ortix is the second shoe shaped from more than 1 million 3D foot scans—and the comfortable fit proves that the technology works.

Karhu’s first shoe based on foot scans was the Karhu Ikoni. Engineers took insights from real Fleet Feet customers’ foot scans to craft a shoe with the ideal fit.

This year, the Fusion gets the data treatment, too.

The redesigned Fusion is soft and comfortable right out of the box, and it works for a range of foot shapes. Fleet Feet testers ran in the new Fusion to see how the data translates into fit and how it feels on the run.

Here’s what we thought of the Karhu Fusion Ortix.

Tech specs

Karhu Fusion Ortix




9.3 oz (women’s); 10.9 oz (men’s)




Everyday trainer




Road, track

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Karhu Fusion Fit and Materials

A pair of men's Karhu Fusion Ortix running shoes

The first thing you notice about the new Fusion is the quality of the materials.

Karhu wrapped the shoe in a sublimated engineered mesh upper that’s free from any distractions or excess hardware. The mesh features a main vent over the toe box and a smaller one on each side, but there isn’t any pattern or decoration over the toe.

The only thing that interrupts the clean upper is Karhu’s M-Lock side panels. The M-shaped overlays provide ample structure to the shoe and lock in the midfoot. Karhu also threaded a pair of cable loops around the second and fourth eyelets to give the laces more to grab onto.

Fleet Feet testers say the fit is outstanding.

“The shoe fits my entire foot really well,” one tester says. “The forefoot has plenty of width, the length is right on and the heel is excellent.”

Hidden underneath the outer mesh, Karhu sewed the tongue into an internal bootie. The bootie runs from about the ankle bone into the toe box, which makes for an ultra-smooth feeling inside the shoe.

Testers like the smooth fabric used inside the shoe, but it did make the shoe feel warm on a few stifling summer runs.

Karhu Fusion Ride and Performance

A pair of the women's Karhu Fusion Ortix running shoes

One of Karhu’s main technologies is called the Fulcrum.

Developed in the 1980s, Karhu’s Fulcrum acts as a pivot point for your foot in its transition from heel to toe to help you move quickly through your gait cycle. Karhu says independent tests show the Fulcrum helps reduce vertical and horizontal oscillation more than shoes without it, which means you bounce less as you run.

Karhu uses three Fulcrum lengths in its shoe lineup: half, three quarters and full. The half-length Fulcrum provides more flexibility in the shoe and less guidance, while the full-length version has the most guidance and least flexibility. The Fusion’s three-quarters-length Fulcrum sits in the sweet spot in the middle of flexibility and guidance.

The Fulcrum is noticeable right when you step into the shoe because it’s made with a denser foam than the rest of the midsole cushioning. One tester says the Fulcrum gives the shoe great arch structure and good rigidity.

“The cushioning is firm and the platform stiff,” she says. “They feel solid and dependable for new runners.

The shoe produces a predictable and reliable foot strike, which is part of what makes it a great shoe for new runners. Our testers didn’t have to fuss with their stride to make this shoe ride comfortably.

While the Fusion feels solid for most runs, our testers say they aren’t the best shoe for speedwork and faster days. Karhu lists the men’s model at 10.9 ounces, and the women’s version weighs 9.3 ounces, which is on the heavier side for fast-day shoes.

“They’re great for easy, recovery days when you want cushion and support or for most runs if you’re a new runner in search of a traditional-fitting shoe,” she says.

A runner holds a pair of the Karhu Fusion Ortix running shoes


New runners looking for a dependable training partner should look into the updated Karhu Fusion Ortix.

With a retooled fit designed using data points from real people, the Fusion is accommodating and comfortable right out of the box.

We love the new fit designed with insights from Fleet Feet's fit id outfitting process, and the premium materials that give the shoe a high-quality look and feel.The cushioning is firm, and the ride is predictable.

We like the Fusion for runs when you feel like cruising or need extra support on recovery days.

Still not convinced? Don’t sweat it. Fleet Feet's return policy means you can test drive your shoes and gear without risk. If you’re not happy with the way your gear performs, looks or fits, we’ll take it back within 60 days. Plus, you’ll get free return shipping on all orders. That's our Happy Fit Guarantee.

By Evan Matsumoto. Evan played many sports growing up but didn’t go pro in any of them. Now, he’s the digital copywriter for and editor for the Fleet Feet blog where he writes about different foam densities and engineered mesh uppers.

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