Clinical Analysis of Running, Running Footwear, and Injury Prevention/Performance. The Doctor(s) of Running, using knowledge of human movement, clinical biomechanics and performance to bring you cutting edge reviews, science and knowledge.

Post Page Advertisement [Top]

Karhu Ikoni Review

Karhu is a company you may not already be familiar with, but it is one that has been around since 1916. When I first saw Karhu, which I learned means "bear" in Finnish, I had a hard time knowing the pronunciation. So let me help you out...it's "car-who". Since this is our first review of a Karhu shoe, let me give you a bit of background on the company. Early in their company's history they created very successful racing spikes that adorned a three stripe pattern that now anyone would recognize as the Adidas logo (who they sold the rights to). Instead of the three stripe pattern, their footwear now has an "M" pattern that is derived from the word "mestari" or "champion" in Finnish. They only recently have been increasing their efforts to distribute in the United States, which is why you may have not heard of them. They have an exclusive partnership with Fleet Feet, which means the only three places you can get their gear is from a Fleet Feet store, Fleet Feet's website, or Karhu's website. The partnership has allowed them to increase their research efforts by collaborating with Fleet Feet and fit id foot scans in the development of their shoe (more on this later).



Let's move on to the Karhu Ikoni. The Ikoni is the newest iteration of the Karhu running shoe line, and it has the two Karhu trademark technologies built in: the fulcrum and ortix. We will dive into these technologies throughout the rest of this review, but let me say that these shoes pack a smooth, fast, and efficient ride. Although you may not have heard of Karhu before this review, the Ikoni is well worth the research. It's time we all know about this brand.

Specifications (per Fleet Feet)
Weight: 11oz (men), 9.9oz (women)
Drop: 8mm
Classification: everyday trainer

FIT/UPPER

I typically wear a size 9 running shoe, and the Ikoni fits great in that size for me. The toe box has plenty of space for my foot, which is slightly on the narrow side, and would expect people with a wider foot would fit nicely in the toe box given its width and the nature of the upper. A good sign of a comfortable upper is that you can forget it is there while running, which has been the case with the Ikoni. It has mesh overlays that create the upper that spans from the forefoot to the heel cup. The mesh upper is a combination of supportive and flexible, and the mesh upper will likely accommodate a moderate to wide foot very well. I run primarily on roads and the Green Circle Trail in Stevens Point, WI. The trail is made of fine gravel and has a good amount of turns in it. During the turns, the upper has felt supportive and I haven't had any lateral shear of my foot. There are some uppers that I have ran in that don't support my foot well and I almost feel like I am going to slide off the side, but the Ikoni has been very supportive without feeling restricting. So far most of my running has been in the cold weather here in Wisconsin (between -10 and 20 degrees Fahrenheit) and my foot has stayed warm enough when going through the tundra. The upper also seems breathable, and on my warmer runs (granted only 52 degrees Fahrenheit at this point) my foot has not felt at all like it was going to overheat.



There is a typical rigid heel cup that spans to the area of the malleoli. The inner surface is lined with a material that is quite smooth and has almost a silk-like feeling. I initially was afraid that because of the smooth nature I would notice a lot of motion in my heel. On my first few runs I did notice this to be the case (but not to the extent that I expected).  However, I performed a lace lock and haven't had any issues with it at all, and it has been very comfortable on my heel. I've grown to like the smooth material as it seems to prevent any friction that would lead to blistering, even when it was moving around a bit.



RIDE/MIDSOLE

I've found that when running in most neutral daily trainers, they all have a similar feel with the only changes coming in the amount of cushioning available. The Ikoni is different. The ride of this shoe is something that has set it apart. I took the pair out of the box and put them on in my kitchen, and I could immediately feel the effects of the fulcrum even with simple walking. Later we will go deeper in to the fulcrum technology of the shoe, but the ride is unbelievably smooth because of it. There is a very soft and cushioned heel that transitions into the 1/2 length fulcrum, which is comprised of a more dense foam. For heel strikers, this gives a very comfortable impact that transitions quickly into forward progression. During my runs in these shoes, I noticed I had less audible pounding through my heel (and I am light on my feet to begin with). Because of the fulcrum and forward propulsion the shoe provides, it responded very well to increased tempo runs.

1/2 Length Fulcrum shown in black foam
Not only is the fulcrum active for a transition from heel to forefoot, but it also has a medial and lateral guidance. This is definitely a neutral trainer, but for those who need some light support, this shoe does offer guidance without trying to control the foot. I found this to come into play on my longer runs when I was becoming fatigued, but didn't provide any guidance when I was fresh. The nice thing about this was that it allowed my foot to do its natural movement, but would help guide excessive pronation and supination when needed. In addition to the fulcrum providing guidance for pronation and supination, the ortix sole added another level of comfort. The ortix was developed through the fit id scans. Instead of having a flat insole of the shoe, like every other shoe that currently exists, they have taken over 100,000 foot scans to develop a slightly curved insole to match the "typical" foot arch. Think the shape of a Birkenstock sandal versus a flip flop you might buy from target. For me this was unbelievably comfortable. The ortix insole made it feel like the shoe was hugging and guiding my arch, but without controlling or giving too much support.


To reiterate, the heel to toe transition is very fast and smooth because of the fulcrum. You will feel the shoe pushing you forwards instead of vertically, and you will notice your calf getting a good workout as well. I had noticeably more delayed onset muscle soreness in my calf after my first several runs in these shoes. The shoe also has an 8mm drop, so it rides in the middle of the trainers out there, which seems to also help with the quick transition to the mid and forefoot.



SPEED

As mentioned previously, this shoe has held up well for my casual runs as well as some tempo training runs (which for me is about 6:30 per mile). Given that the fulcrum promotes forward progression, the shoe almost promotes a slightly faster run and I found it difficult to slow myself down when doing recovery runs or casual runs. I plan to use this for both my short tempo runs as well as my moderate to long runs where I want to put some effort in. It is a very versatile shoe that can handle many different types of runs, including some higher paced half marathons or even 10Ks. Although it feels lighter than its true weight, it is the weight of a trainer and I wouldn't necessarily consider this a shoe for high speed and shorter races.

DURABILITY

This shoe hasn't changed an ounce since I've started running in them. The blown rubber outsole doesn't seem to have any wear, and the midfoot and heel cushioning do not seem to have lost any of their responsiveness or support. The ortix insole has only gotten more comfortable as the foam has continued to accommodate to my foot. From talking to others who use this shoe, people have gotten 500-800 miles on it without the outsole wearing and the fulcrum midsole holding up very well.



THOUGHTS AS A DPT 

Karhu has done an impressive job of integrating research into the development of their shoe. We will dig into the research they have done as well as offering some additional thoughts regarding biomechanics and workload that are implicated with the technology in this shoe.

One caveat first. You will likely hear this from me several times during my reviews, but no matter how incredible a shoe is, it likely will not be your savior when it comes to staying injury free or when recovering from injury. We need to make sure that as runners we have a strong base to run off of and ensure proper mechanics that aren't predisposing us to injury. That said, a shoe can definitely be an outstanding tool in running well and avoiding injury, and I think the Ikoni is potentially a great tool for your tool belt.

The first piece of technology is the fulcrum. The goal of the fulcrum is to promote forward progression versus vertical oscillations while running. Karhu did a study comparing vertical movement when wearing a Karhu verses another top brand, and they found up to 11.9% less vertical translation when a person wore the Karhu versus the other brand. What does this change result in? Two things. First, the goal of running is to move forwards, not up and down. So if you find yourself moving up and down while running, you are wasting energy to move in a direction that isn't productive for your training run or race. In essence, you would lose a lot of efficiency. Karhu looked at oxygen consumption and did find that people running in Karhu versus a comparable shoe had 1-4% less oxygen consumption, meaning they were more efficient. This improvement in energy consumption is linked to the improved forward progression the fulcrum promotes. Second, there is a potential for there to be a change in ground reaction forces (GRF). This hasn't been studied yet, but if there is less vertical translation, there is the potential for lower impact forces to be passing through your ankles, knees, and hips when landing each step. Lower impact could potentially be beneficial for protecting joint surfaces, particularly our articular cartilage. Regardless of the shoe you are in, we all need to make sure that we have adequate shock absorption and aren't "pounding" through stiff joints. So the Karhu may have potential to help decrease some of the GRF, but we all still need to make sure we are strong and have good form when we run to prevent long term effects to our joints when we run.
Slide from Karhu research presentation
Another finding in Karhu's research that is related to the fulcrum was increased calf activation. The fulcrum promotes a very quick transition from the heel to the mid and forefoot, which necessitates activation of the calf muscle to control forward progression of the tibia. The studies found that there was a 7% increase in calf propulsion compared to when wearing other comparable brands. What we need to remember is that an increase in work in one area means a decrease in another. And what they found is that with the increase in calf propulsion there was a concomitant decrease in knee extensor moment (decreased quad use). This could be a great thing, especially for those with a patellar tendinopathy or some cases of patellofemoral pain. However, these benefits hinge on some of the things I mentioned in my caveat above. If you don't have adequate calf strength (just like if you were to transition from a heel to forefoot strike), you will likely have to wean into these shoes. Also, you have a potential for excessive tibial movement in your mid to late stance which could end up putting increased stress through the knee. You also have to recognize your calf will have to adapt to the new load being put on in, again just like if you were to transition to a forefoot strike or wear a zero drop shoe.

Another great piece of technology in the fulcrum is the medial to lateral guidance (pronation/supination). Instead of simply putting a medial post on the shoe, the fulcrum provides both medial and lateral support to guide the foot during your heel to toe transition. This again has impacts on efficiency, but also can help decrease eccentric strain on the tibialis posterior and other muscles around the ankle. Other shoe companies are starting to follow suit (like Brooks with the guiderails and New Balance with their roll bar), but Karhu has been on the front end of this trend. The Ikoni has a 1/2 length fulcrum as mentioned above, which means it guides the foot during less of the gait cycle. If someone needs more support and has more excessive pronation or supination, Karhu makes shoes with a longer fulcrum that gives support during more of the gait cycle.



There is actually more research (believe it or not) done with this shoe including line of progression of the center of pressure (COP) as well as tibial angle at impact, but we just don't have time to go into it all deeply. Just know that the COP had little deviation from center, improving efficiency, and the tibial angle at impact is decreased compared to when runners wore other shoes. This is important, as high tibial angles at impact are linked to different running injuries. So...two more biomechanical benefits of the Ikoni!

Give your body time to adapt to a shoe like this, but the shift to the Ikoni is completely worth it. It only took me a week to get to my normal milage in this shoe, by the way, so the transition doesn't need to be too drawn out. However I will say that if you are noticing achilles irritation or posterior tibialis pain, it might be a sign to work some other shoes into the rotation and work on calf strengthening and endurance (or see your local physical therapist to find the root of what is going on). The impact of the technology put in this shoe has a very positive impact on the biomechanics, efficiency, and workload during running. Well done, Karhu.

WHO THIS SHOE IS FOR 

Karhu has done a fantastic job with this shoe. If you are someone who is looking for a neutral shoe that can handle both some pace and distance, this is the shoe for you. For those looking for a shoe to help you complete a marathon, this would be a great option for you as well. It's a shoe that will give you help when needed, but will not feel like it is controlling your foot. Strap these on for a cushioned yet responsive ride while feeling like your foot is getting a hug from the ortix insole and the comfortable upper. The Ikoni is a great addition to your daily trainer rotation and may just become your new go-to shoe, as it has mine. Plus you can see the my little guy, Henry, digs them too.



GRADING

Fit/Upper          9.5/10
Ride/Midsole    9.5/10
Stability            10/10
Speed                8.5/10
Durability          10/10

Total Score: 95%

Thanks for reading!

Editor's Note (Dr. Klein): As always, the views presented on this website belong to myself or the selected few who contribute. This website should not and does not serve as a replacement for seeking medical care. If you are currently injured or concerned about an injury, please see your local running physical therapist. If you are in the Stevens Point area, Dr. Nathan Brown is currently taking clients for running evaluations.

Dr. Nathan Brown PT DPT MS
Doctor of Physical Therapy
Point Forward Physical Therapy

***Disclaimer: These shoes were provided free of charge for clinical use and a trial to assist in determining which patients may benefit from this shoe.  We thank the  people at Karhu for sending us a pair.  This in no way affected the honesty of this review. We put at least 50-75 miles on trainers and 10-25 miles on racing flats prior to reviewing them. Currently I have 54 miles on my pair. My views are based on my extensive history in the footwear industry and years testing and developing footwear. If you are a footwear rep looking for footwear reviews or consultations on development, we are currently looking to partner with companies to assist, discuss and promote footwear models. Partnership will not affect the honesty of our reviews.

Like and Follow Doctors of Running
Facebook: Doctors of Running  Twitter: @kleinruns
Instagram: @doctorsofrunning Direct Contact: doctorsofrunning@gmail.com

Please feel free to reach out, comment and ask questions!

Featured Shoe Review: Skechers GOmeb Speed 6 HYPER

Running Movement Impairments

Running Movement Impairments: Overstriding

A great deal of attention in the running, biomechanics and medical world is being paid to how people move and how that can affect performanc...

Bottom Ad [Post Page]