Physical Therapists Using Clinical Analysis To Discuss The Art And Science Behind Running and The Stuff We Put On Our Feet

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Karhu Ikoni 2020 Multiple Tester Review

     The Karhu Ikoni is the first shoe from the Karhu training line to incorporate Ortix fitting and 3D scans of different runner's feet to get the closest and adaptive fit for all feet. This is the most neutral of the training line featuring a 1/2 length fulcrum to help stabilize the heel and midfoot. The overall design is built to create Karhu's Rolling Effect, including a bevel in the heel and a slight toe spring. The result is a smooth ride for many foot strikes.

Specifications (per Karhu)
Weight: 10.9 oz (men's 10), 8.9oz (women's 8)
Stack Height: 24mm/16mm
Drop: 8mm
Classification: Daily neutral trainer, max flexibility, minimal stability/guidance 


David: The Karhu Ikoni 2020 is a daily trainer with an incredibly smooth ride that runs much faster than it's weight. The half length fulcrum does a good job of stabilizing the heel and midfoot lightly while still allowing for flexibility and a neutral ride. The upper is one of the best I have ever put on my foot, allowing nice lockdown and a pleasant toe splay. This is one of my favorite trainers for the beginning of 2020. 

Nathan: Much of my review is going to be comparing the current 2020 version of the Ikoni to the previous version, which I personally really enjoyed. Star updates come in the form of an improved fit in the toe box, an upgrade to the upper, and smoothing out the half length fulcrum to create a more natural transition to the forefoot. This is a shoe that has a great shape, build, and stability mechanism built in that can be suitable for many types of runners.


David: The Karhu Ikoni 2020 brings updates to it's upper in all the right ways. The upper features their Ideal Knit upper created with the help of the Ortix 3D scans and fits true to size in my 9.5. The upper breathes incredibly well and hugs the foot very well. The heel has a semi rigid counter with a lot of padding to ensure a good hold on the heel without any slippage or translation. The M lock update helps create a snug lockdown over the midfoot when lacing down the shoe. The midfoot is nicely held as is, and can lock down snug with the lacing design if desired. The forefoot is wide and tapers off slightly laterally to create a natural fit, relatively wide toe box, and natural pattern when running. There is a relatively thick toe guard that holds together the forefoot that can rub slightly, though not problematic. I would like to see it thinned out a little though. 

Nathan: Best part of this update is the larger volume toe box, even in the traditional width option (their non-HiVo). The overall fit of the shoe is on the snugger end, but there is more adaptability through the midfoot and proximal forefoot. Many of my patients had tried the previous version and had issues with the toe box creating some numbness in their feet, but not so with the new version. The only downfall for me was the movement away from the padded tongue of the previous version. They transitioned to a thin tongue with stitching along the edges, which was irritable on my skin if not covered by a sock. This shoe does have the same silky heel counter and sock liner as the Synchron (which posed some issues with lock down), but given the tighter fitting upper, this was not a problem and I did not have any heel slippage. 


David: The Karhu Ikoni 2020 does a good job of implementing Karhu's "Rolling Effect". The 8mm drop is hardly noticeable with how smoothly this shoe transitions from both rearfoot/heel and midfoot to toe off. The "guidance" from the shoe is primarily in heel and midfoot, and then allows for the runner utilize a neutral and less stable toe off for the neutral lovers. The fulcrum looks like a slightly curved shank (not a shank though) in the midfoot with a parallel line in the heel, keeping the pressure point of the heel free. The heel is beveled posterior laterally and rounded to smooth out the transition nicely. The AERO FOAM midsole is firm, though plush enough for daily mileage. Though the ride of the shoe is smooth and fast, the foam is a little underwhelming and definitely does not give as much rebound or responsiveness as some of the other midsole foams on the market. Overall, great ride though. 

Nathan: Before comparing to the previous, I think this is worth noting. The midsole foam of the Ikoni is nothing "special" underfoot. But even though that is the case, I absolutely love the ride of this shoe. Karhu has the shaping of the midsole down pat to create a really smooth and enjoyable ride. The slight bevel creates a soft landing, the half length fulcrum provides a guided, smooth, and quick transition to the forefoot, and there is just enough toe spring and flexibility for a smooth toe off. In comparison to the Fusion and Synchron, this is by far my favorite ride because of how the transition off the fulcrum really pushes you forward (they've sent me their research showing decreased vertical oscillation while wearing the Ikoni). In comparison to the previous version, they really smoothed out the transition off of the fulcrum. Whereas you could feel the "drop-off" in the older model, the 2020 is smooth without a notable transition off the fulcrum, which is a huge bonus. If Karhu can pack a more exciting foam in here, watch out.


David: This is the most neutral and least stable of the Karhu trainer line, though still relatively stable for a neutral shoe. The relatively firm ride creates good ground feel and a decent amount of stability for the shoe. The fulcrum also creates a little stability through the heel to the posterior midfoot and creating a linear pathway. The upper holds very well through turns and locks down well. The toe guard is noticeable on downhill decsents however, with a slightly spacious toe box. 

Nathan: This shoe defines dynamic stability for me. The fulcrum of the shoe is made of a denser foam that spans all the way medial to lateral and also almost all the way from the top to the bottom of the midsole. This allows for the fulcrum to function exactly as it is shaped and isn't "muddied" by being sandwiched by softer foams or having a top sole. The fulcrum can give some mild guidance for those who land on the heel all the way through the midfoot, and then the platform is wide with some lateral flaring through the forefoot, creating a stable push off. For a neutral shoe, you get a lot of stability, especially during those later miles.


David: This shoe is surprisingly fast for the weight and build of the shoe. The rocker and toe spring design create a very fluid ride that responds pretty well at a good range of paces. The shoe doesn't necessarily want to "push" the pace, but stays smooth when you actively begin to push the pace. I think in large part that is due to mild/average responsiveness of the foam. However, I do have several 5:45 or faster miles on these shoes and they have felt good during both fartlek and daily training efforts. It is just shy of being able to hit workout paces though. It's not quite a "do it all" trainer, but could be a shoe to stand with giants with a midsole update. 

Nathan: Because of the shaping of this shoe, it is remarkably fast for its weight. I do find that I end up running 10-15 seconds per mile faster than I am planning on doing whenever I wear the Ikoni (yes, this is very subjective...but still true for me). Although not a true tempo shoe, it did well for longer fartleks and mild tempos on longer runs. There is plenty underfoot, so it can take the milage.


David: The durability of the Karhu Ikoni 2020 is very average and the least appealing to me. In the portions of the outsole that does have durable rubber there is plenty to burn though. However there is also a good amount of exposed midsole as well. The exposed foam showed early wear, but has held up a little better than I initially thought it would. The foam and ride of the shoe should remain consistent throughout wear. Durability isn't necessarily an issue, but nothing spectacular either and should last a normal 250 to 300 miles that daily trainers are expected to last.

Nathan: Very different experience for me than David when it comes to durability. First, the rubber that is there has shown almost no wear for me (same as my previous model which had about 100 miles on them with no wear). The exposed outsole is only slightly worn, but it is in places that won't impact the ride or performance of the shoe, so I'm not worried. The midsole has not changed. But again, the midsole isn't the magic in this shoe, it's the shape, and therefore I see this shoe lasting much longer than the factory standard for me. Likely over 500 miles easy. 


David: So far I have been able to get my feet in the Synchron 2020, Ikoni 2020, and Fusion Ortix 2020 and have found that the Ikoni does the best job of creating the "Rolling Effect". For this section I want to focus on how Karhu delivers the smooth rocker that keeps momentum forward. It begins with the heel, where Karhu does a good job of gradually curving the heel with emphasis in the posterior lateral direction where most people land. After loading response the shoe loads into the fulcrum that creates a small level of spring and stability through the midfoot. Ultimately there is a small toe spring (gradual curving through the forefoot) to help smooth out the toe off portion of gait. The result is a ride that moves through all of the rocker points smoothly but still maintains some responsiveness with the triple action fulcrum through the midfoot. This helps maintain a linear pathway, while still leaving some of the work to the runner to push off at the end. For their neutral trainer, this is a clever design to stabilize the initial landing while still allowing for the runner to use their own ankle mechanics and musculature to finish the gait pattern from midfoot to toe off. 


David: I really like the Karhu Ikoni 2020, but I do have a few recommendations. Though this is one of my favorite uppers in the game, I think the toe guard could be shaved down slightly or done without. I also think the midsole could be updated to have more rebound and responsiveness to accompany the beautiful ride of the shoe. I would also like a little more durability to the outsole if possible.

Nathan: I really enjoy this shoe. One thing I would recommend is keeping the fulcrum as is for this shoe and not transitioning to the type used in the Synchron 2020. Second is to add a new, lighter, and more responsive midsole (I know...easy, right?). That could really make this shoe shine.


David: The Karhu Ikoni 2020 is a wonderful daily training option for those that like neutral rides. The shoe is pretty versatile for its weight and can handle fartleks and long runs very well. The upper is one of the best in the game and shoe has a nice fluid "Rolling Effect" to it. Durability could be better, but this is definitely a neutral shoe to look out for! 

Nathan: The Karhu Ikoni 2020 is a daily trainer for those who want to get a lot of miles out of their shoe and have the option to do some slightly faster work as well (but aren't worried about top speed). This shoe can handle high milage, and may provide just enough stability for those who need a little guidance. This is a versatile shoe in that it is possibly appropriate for many foot types and runners.


Fit/Upper        9.75/10 (GREAT fit, toe guard too involved though and presence felt)
Ride/Midsole  9.25/10 (Very fluid ride, great rolling design, midsole could have more rebound)
Stability           9.5/10 (upper holds well, good ground feel, forefoot spacious but hits toe guard)
Speed               9.25/10 (build and design help maintain pace if pushed, though midsole average)
Durability      8.5/10 (ride and foam should hold, outsole wear early, normal durability overall)

Fit/Upper        9.5/10 (-0.5 for irritability from tongue)
Ride/Midsole  9/10 (-1 for lack of responsiveness in foam, high marks for smooth ride)
Stability           10/10 (stable throughout, lateral flaring in the front and fulcrum in the back)
Speed               8.5/10 (-1.5, not responsive or light enough for true tempo work)
Durability      9.5/10 (Foam and fulcrum looking great, minimal outsole wear)

TOTAL (%): 92% D, 93% N


Dr. Klein is a 140 lb male with notable PRs of 14:45 5k, 31L36 10k, 1:11:11 half marathon and 2:32:44 for the full marathon.  He typically runs 70-100 miles per week and trains at a variety of paces from 8min per mile recovery runs to 4:40 per mile 1k repeats.  He prefers firmer and responsive shoes with snug heels and medium to wide toe boxes.  He is particular to less cushioned and close to the ground shoes, but can handle a little cushion when he gets beat up.  IG handle: @kleinrunsdpt

Dr. Salas is a 135 lb male with notable PRs of 3:54 1500m, 14:56 5k, 31:06 10k, 1:08 for half marathon. He typically runs 40 to 50 miles per week and trains from about 7:30 recovery runs to fast shorter efforts at 4:30 pace. He normally prefers neutral shoes with a firmer ride, but is completely open to other types of shoes.  He is a footwear enthusiast at heart and will always appreciate a high quality shoe when it comes around. For updates on training or testing, IG handle: @docsofrundavid

Dr. Brown is a 155 lb male with notable PRs of 19:18 5K, 39:25 10K, 1:33 half marathon, and 3:54 marathon. He typically runs between 20-40 miles per week at a variety of paces from 8-8:30 min/mile for recovery runs to 6-6:45 min/mile for tempo runs. He typically prefers shoes that provide some cushioning underfoot but still maintain a more firm and responsive feel. Current goals for 2020 are to break the 1.5 hour half marathon and 3:30 marathon.

Thanks for reading!

Editor's Note: As always, the views presented on this website belong to myself or the selected few who contribute to these posts. 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 Los Angeles area, I am currently taking clients for running evaluations.

Doctor of Physical Therapy
Board Certified Orthopedic Clinical Specialist
Fellow of the American Academy of Orthopedic Manual Physical Therapists

Nathan Brown PT DPT MS
Doctor of Physical Therapy 
Masters in Anatomy and Clinical Health Science
Movement Performance Institute Certified in Advanced Functional Biomechanics 

David Salas PT DPT CSCS
Doctor of Physical Therapy
Certified Strength and Conditioning Specialist
***Disclaimer: These shoes were provided free of charge in exchange for a review.  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 35-75 miles on trainers and 10-25 miles on racing flats prior to reviewing them. Currently we have 36 (David) and 35 (Nathan) 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.

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