R&A Cycles Perspective
Karhu is all about making running shoes that make running easier, and a great example of this concept is the Flow3 Trainer_Fulcrum, which I had the chance to try out during the last week.
For those that run frequently, why wouldn’t you want to enjoy running longer, faster, and smoother than ever before? The Flow3 Trainer_Fulcrum achieves this with Karhu’s fulcrum technology. Coming standard in all Karhu shoes since the ‘80s, in its simplest form the fulcrum is an inverted triangle of denser foam submerged into a cushioned midsole. Positioned where the front of the heel and the back of the arch meet, it lies directly under that ambiguous spot called the midfoot, where it acts as a pivot for your weight as you move through your footstrike. Independent research conducted by both the University of Jyväskylä in Finland and Iowa State University has demonstrated that runners experience less vertical and horizontal oscillation and a better midfoot landing position when compared to both traditional running shoes and barefoot running. Translation: running becomes less about up-and-down, and more about you going forward.
And the Karhu fulcrum works. I run primarily bike paths, and while it’s not distracting, when I ran in the Flow3 Trainer_Fulcrum I did notice a pleasant little zip through my stride and a more solid feeling underfoot, like I was landing solidly and squarely on the midfoot.
While I personally contact the ground at the midfoot, because of its position, Karhu’s fulcrum technology works with a variety of footstrikes, making them all easier and more efficient. Say you heel-strike? The fulcrum acts as a pivot, transitioning you through to that midstance faster, with a slight nudge of momentum. It’s shocking how smooth it becomes when rolling from heel to toe. Say you’re a mid-foot striker like me? You’re halfway there, and the fulcrum tips you through that initial contact toward the forefoot and to the push-off. And those of you that have a pure forefoot canter? Sure, that front foot may come down first, but that heel does eventually settle, and you’re still going to enjoy the forward momentum it gives you as your weight switches to move off your toes again. Every footstrike can benefit from fulcrum technology.
Did I mention it’s light? The Flow3 Trainer_Fulcrum is super lightweight, but still maintains a pleasant amount of cushion. It handled the asphalt I run like a champ. A firmer foam underfoot gave me a lot of ground awareness, but it wasn’t so minimal that I felt like I was banging from stride to stride. The carbon rubber outsole gave the shoe a snappy, poppy contact similar to what I’d expect from a racing flat, especially with the full-contact bottom, and the flexible forefoot really moved when I threw in a stride or two for turnover. I think of it as a shoe with the nimbleness of a racing flat, but with the cushion of a lightweight trainer, and for that reason Karhu classifies it as a hybrid between the two, for racing distances up through marathon.
The upper itself feels amazing on the foot, and when you find out about all the little design features that comprise it, it’s not hard to understand why. “Achillows,” or little foam cushions that cradle the Achilles tendon, are comfy and supportive, and an anatomically mapped tongue helped hold my foot securely while protecting it from the laces biting in when they were cinched down. The sculpted air mesh that makes up the majority of the upper was breathable and kept my feet dry without being overly drafty.
As far as fit, expect the Flow3 Trainer_Fulcrum to fit a medium width in the forefoot and a more generous heel.
All things considered, I had a great experience with Karhu’s fulcrum technology, as exemplified by the Flow3 Trainer_Fulcrum. It’s a firm, responsive shoe that could handle the miles of a typical training run, but felt light enough to race some longer distances from the half marathon to the full marathon.
