Groundbreaking Flywheel Devices Soon to be Launched

Yes, the rumours are true. We’ll soon be launching no less than four new Exxentric flywheel training devices.

We have always been focused on refining our kBox line of equipment to meet your high demands on quality, cost and functionality rather than quickly establishing a broad product portfolio.

However, with the kBox now in its fourth generation, we are proud to announce that we will soon present a major product launch including two brand new devices, matching the feedback from our users in now almost 60 countries on 6 continents.

Besides enhanced specs, new smart accessories and more, you’ll get a new entry level price which should appeal to a broad audience of both professionals and amateurs – and a completely new option for horizontal exercises!

There are exciting weeks ahead for the world’s flywheel training pros, as well as everyone serious about their strength training.

Join Exxentric at the CSCCa National Conference to get a sneak peek already this week if you are in the US, and stay tuned on our social media channels to be the first to learn more.

Erik Lindberg

/Erik Lindberg, CEO

Announcing New and Redesigned kBox Features

Exxentric’s Head of R&D, Fredrik Correa announces new and redesigned kBox4 features for optimizing your training.

Key points:

  • Multiple updates for improved durability, functionality and quality
  • Now included with all new kBox4 orders
  • Upgrade discount for existing kBox4 owners until March 15th!

Not all announcements have to be game changers, some can be impressive product developments we have been formulating for all of you! Our R&D team has been actively working on some exciting advancements that will be announced in the upcoming months but in the meantime, we are happy to announce a few side projects we have been working on that have now been rolled out.

To us, quality and customer relations are of key significance. After listening to all of you we came up with a few ideas on how to improve your flywheel training experience:

Rubber Pulley Protector

Many of our users really like to go all-out when using the kBox. When going hard on the kBox, on occasion you may not be able to completely absorb all of the energy you have just generated, this results in a collision between your kBox and the attachment Pulley. While we do like seeing our kBoxes being pushed to the limit, letting the pulley collide with the kBox is not recommended for maintaining good condition in the long run.

For this reason, we have designed a new and robust Rubber Pulley Protector. I still recommend avoiding heavy collisions between the Pulley and the kBox but if it does end up dropping in the hole, your gear will now be better protected. Moving forward we will be including this new protection feature with every kBox, and handy users can even upgrade their existing Pulleys.

Angle Adjuster

With the kBox3, it was extremely easy to use Foot Blocks when positioning yourself for some really nice bent-over rows. But with the quick lock solution on the kBox4, we needed to come up with a separate solution for this feature. Having prioritised other key features from the start, we are now happy to be able to offer you a robust and very simple Angle Adjuster. For a quick demonstration of the Angle Adjuster, watch clip.

This piece is now also included with every kBox shipped moving forward. If you already own a kBox4, don’t worry, get in touch with us to get your own Angle Adjuster.

Flywheel Sleeve

We know one or two things when it comes to training – flywheel tFlywheel sleeveraining and mechanics in particular. However, when we initially embarked on this journey, we were far from packaging experts and some of the solutions weren’t as presentable in the beginning. But it is safe to say that we have definitely improved over time.

One of our latest projects has been to design a Flywheel Sleeve that will cover and protect your flywheels during transportation and in your gym. We liked the idea of offering a more visually appealing kBox when opening your package, while also reducing waste and making the packaging more reusable. The Flywheel Sleeves are available in all sizes and now come with any new kBox or can be ordered separately.

Get Your Upgrade

Creating molds, prototypes and then eventually producing custom-made products must make a new kBox4 system more expensive, right? Well, don’t worry, we will be absorbing all those costs and our prices will stay the same. In addition, all existing kBox4 owners can get an upgrade at a small cost. We are happy to offer a 50% discount on these items until March 15th!

The list prices (before the discount) for back orders are EUR 11 / USD 13 for the Rubber Pulley Protector, EUR 16 / USD 19 for the Angle Adjuster and EUR 9 / USD 11 each for the Flywheel Sleeves, plus shipping and tax. To get yours, just contact us or your reseller today.

I know you all have great ideas about how we can improve, so keep the ideas coming. We do what we can with the resources we have and take all ideas into consideration, I promise!

Happy DOMS

/Fredrik Correa, Co-Founder

The kMeter App Now For Android

Finally, the benefits of the kMeter App for digital training feedback are now available also for our Android users, with a special upgrade offer.

Ever since the release of the kMeter feedback system we have received questions about an Android app, so we are of course happy to be able to offer this now to all of our Android users following a busy autumn.

The kMeter App for Android is now free to download for all users of a kBox equipped with the kMeter Module.

Just like the iOS app, the new Android version offers real time tracking of concentric and eccentric power output and more, as well as storing, sharing and exporting your data.

The Android app is similar to a recent version of the iOS kMeter app (2.1), and we are now starting the work to implement the latest few changes from updates 2.2 and 2.3 into the Android version as well.

Try it out

If you already have access to a kBox with the kMeter Module, we are hoping that you will download the new Android app and try it out.

Please let us know if we missed something that should be added to the next update. Since Android is run on many different devices from different manufacturers there might be issues that we haven’t encountered in our internal testing. Also, we would love to see your rating of the app on Google Play!

To read up on the kMeter or watch a video introduction, start at the main page about the kMeter here.

upgrade Offer

We always try to take special care of our existing users. If you did not add a kMeter Module to the order for your existing kBox system, we are now offering shipping for free for all upgrade orders for kMeter Modules before January 15th. Contact us today for a quote or if you have any questions.

So, tell your friends, test it and let us know what you think. Why not start 2018 with a baseline kBox Power Test and then take it from there?

Happy DOMS!

/Fredrik Correa, Co-Founder

New High-End Systems and Free Global Shipping

Today, we are launching our most complete kBox configurations so far, and celebrating this by offering free global shipping on any system ordered before December 31st.

We have been working hard this year to increase production capacity and meet your rapidly increasing demand. This has included adding accessories such as the Flywheel Bag and the Accessory Rack, and increasing the range of sizes available for the Harness and Hip Belt.

New High-End Systems

To secure that we have a recommended system that offers the most complete current configuration, we are now proud to present the kBox4 Pro Ultimate System.

This new high-end system caters to the needs of our most demanding customers, including strength and conditioning teams at the largest sports clubs, leading physiotherapy clinics and premium personal training studios. The kBox4 Pro Ultimate System is priced at €5,130 / $6,010, which includes all the accessories mentioned above – and more.

In addition, there is now a high-end system available for the Lite platform, called the kBox4 Lite Advanced Plus System, with an almost as complete configuration, priced at €3,790 / $4,450.

Meanwhile, our Starter and Advanced system configurations remain, with pricing from just €2,190 / $2,570 for the kBox4 Lite Starter System.

Free Shipping in December

Celebrating the new high-end systems, starting today we are offering free shipping worldwide for orders of any kBox4 system. Hence, only local taxes (if any) will be added to the above prices. This offer may not be possible to combine with other campaigns, and it is valid until December 31st.

We are currently fully stocked, and ship most orders within one business day. To see the full specifications and get a quote for any system, contact us today.


New Advanced Functions in kMeter 2.3

The latest version of the kMeter App has now rolled out, including several new features solely based on user request. Fredrik Correa explains:

Summary of new functions:

  • Discard reps before saving
  • Import users
  • Delete users

This release is special since all new features are solely based on user feedback and suggestions. After talking to different users I came across various interesting questions such as:

– “My athlete stopped one rep short of the set so the last rep was spoiled, how can I edit that?”

– “I want to do a unilateral drill but work both sides in one set but during the switch I loose a couple of reps, is there a setting for this?”

– “Our facility has multiple kBoxes and we would like to spread the user data (not the training data) over multiple iOS devices, how can we do this?”

Given that my answers would have normally been either “there’s no such feature” or “this would need to be done manually”, these questions made me realise our app’s limitations and how it could be improved.

Before you continue reading and start pulling your hair. We understand these new features are slightly more complicated than previous ones, so we compiled a .zip file containing instruction and templates for importing users here if you need it.


After completing your set and viewing your summary you can now press ‘EDIT’ and you will get a list over every rep (not the pre-reps) in a list. Here you can select the reps you want to discard and they will be taken out of the summary and your metrics will be re-calculated based on the data without those reps.

So if your athlete stopped one rep too short or lost balance in the 2nd rep you can easily just click that one away and save the data like before.

As for the second question, if you want to do 10 single arm rows on each side, you can set up the app with two pre reps and 22 training reps. You start with your two pre-reps followed by 10 training reps and then you switch over and do two (pre-)reps with the another arm and the following 10 training reps. Before saving you will have to discard those two extra reps in the middle of the set (rep 11 and 12) after you switched arms. Watch video.


If you are using the kBox with a whole athletic department of a bigger team and use multiple kBoxes and iOS units, the user data would have been quite difficult to set up. Not anymore.

Now you can set up a .csv file with all you users and import it from an email, google drive or iCloud. You still have to approve every user but it’s much faster and you can send out the .csv to the other coaches for them to add in their devices. When doing this we also added the function to delete users to clean up your user list. Here is a step-by-step guide how to set up the .csv file (or download our templates) and how to import them. Watch video.


We had our multisystem users in mind when we added the import function but sooner or later deleting users would be required too, so we added that feature in the Set Up > User menu. Just select the users you no longer need to track and press delete. Watch video.

Existing kMeter 2.2 Features

These improvements come on top of the current kMeter features that were already available before today’s release:

  • Real time data of average power, peak concentric and eccentric power.
  • Graphic, numerical and voice feedback.
  • Set limit based on reps, time or power drop-off% for traditional, metabolic or VBT based training.
  • Set summary with power, force, displacement, average and peak speed, relative peak power (W/kg BW), rep time, kcal expenditure and more.
  • Multi user, create different users with DOB, gender, height, weight and switch easily from the front screen.
  • Editable data, change drill, user, VAS score from previously saved data.
  • Landscape mode in device or on TV via AppleTV.
  • Share screen of summery to camera roll.
  • Database with possibility to share all or selected data in a CSV compatible file.
  • Filter data in the database based on user.
  • Research mode (send raw data from a set).
  • Edit exercises (change the order they appear in, insert new exercises or delete existing ones).

For a quick demo of the new features check the full video below.


Wrapping Up

Thank you for your feedback, keep it coming! Now, go download version 2.3 of the kMeter now on iTunes.

Happy DOMS!

/Fredrik Correa, Co-Founder


Guest Article: kBox and Eccentric Overload in Archery

Today, we have the honor to present a guest article for download from a long-time kBox user, sports performance consultant Antonio Robustelli.

This is the first part of two pieces about the use of eccentric training with archers and how he implemented the kBox leading up to the 2016 Olympic Games in Rio.

Research is a great driver in our field, but the practical experiences shared by coaches and physios are no less important. Our goal is to help our users by offering knowledge from both these areas, and that’s why I’m very happy to present a two part guest article by one of our successful users willing to share his insights.

Antonio is an Italian high level educator and CSCS certified performance coach that has been using the kBox for over two years with all types of athletes (LinkedIn, Twitter). In this first article, he is providing an overview about the importance of eccentrics in sports in general and in Archery in particular. In the second part, he will provide some info on how they programmed their training running up to the Rio Olympics and how it helped his athlete Claudia Mandia to secure the fourth place with the Woman Italian National Team.

We have arranged for you to present yourself to download the article here:

I hope you will enjoy the reading and I would be happy to share more insights from you, our users and coaches if you want a platform to do so. Sharing is caring.

Happy DOMS!

/Fredrik Correa, M.D., co-founder

Introducing kMeter 2.1 at the CSCCa National Conference

On site today at the National Conference of the Collegiate Strength and Conditioning Coaches Association, we are proud to introduce version 2.1 of the free kMeter app, providing reliable exercise feedback for kBox users. The kMeter now includes editable exercise list, research mode and more:

So, what were we able to add in the new version 2.1? If you are in Orlando this week, just stop by booth 928 at the CSCCa conference for a personal demonstration ? or keep reading:

Edit Exercises

Change name, order of the existing drills or remove or add your own drills. By changing order you can make sure your favorite drills are at the top of the list saving time for you saving data. Create your own drills and no need to write long comments and having to keep track of them.

I think many of you will like this possibility to edit your own exercise list. Let us know if you use it!

Research Mode

By turning this on the share button in the summary turns in to a raw data dump into an Excel-compatible file giving you the rotational data for every 40 ms reading. This is a feature some have asked for, and now you got it.

Minor Fixes

We made a few fixes regarding W/kg in the relative power calculations and file compability when sharing data to Excel.

Existing kMeter 2.0 Features

Before we wrap up, let’s briefly go through the current kMeter features that were already available before today’s release:

  • Real time data of average power, peak concentric and eccentric power.
  • Graphic, numerical and voice feedback.
  • Set limit based on reps, time or power drop-off% for traditional, metabolic or VBT based training.
  • Set summary with power, force, displacement, average and peak speed, relative peak power (W/kg BW), rep time, kcal expenditure and more.
  • Multi user, created different user with birthdate, gender, height, weight and switch easily from the front screen.
  • Editable data, change drill, user, VAS score from previously saved data.
  • Landscape mode in device or on TV via AppleTV.
  • Share screen of summery to photo roll.
  • Database with possibility to share all or selected data in a CSV compatible file.
  • Filter data in the database based on user.

For a run through of the new features, check out the video below.


Wrapping Up

Thank you for your feedback, keep it coming! Now, go download version 2.1 of the kMeter now on iTunes.

Happy DOMS!

/Fredrik Correa, Co-Founder


James Harden’s Hidden Athleticism and How the kBox Improves Basketball Performance

Basketball is a sport where you don’t necessarily have to be the fastest to succeed and James Harden of the Houston Rockets has been demonstrating that all throughout this season as well as his entire career. Here’s how flywheel training on the kBox can help to unlock your potential on the basketball court, as changing speeds is not just about your explosiveness.

To anyone that doesn’t follow the NBA, James Harden has just wrapped up a historical season leading the league in assists, while averaging a stat-line that hasn’t been seen since Oscar Robertson and producing the most points per game for his team since Wilt Chamberlain in 1961-62, all while leading his team to the third best record in the NBA. Simply said, what he’s accomplished this season is amazing.

I remember how at one point during the season I was listening to a podcast where it was quickly mentioned as a side note that P3 Applied Sports Science, who have worked with over 100 NBA players, measured James Harden’s athletic abilities and found out that he was average to below average in most categories. While being one of the best basketball players on the planet, his physique certainly doesn’t stand out as much as that of LeBron James or Russel Westbrook. So, finding out that he’s not one of the most athletic players in the NBA is definitely not a surprise. But knowing this, what is it then, besides the cognitive portion of the game, that gives him such an enormous edge over the rest of his peers in the NBA?

It turns out that James Harden is elite at decelerating, according to Marcus Elliott at P3. His exact words are “Harden is barely average in almost every metric we look at related to athleticism, except for deceleration metrics, and in those he’s one of the best athletes we’ve ever measured in any sport — in soccer, football, or basketball.” Anyone who’s ever played basketball knows how important change of pace is but when striving to become better players, both athletes and coaches often focus on acceleration and explosiveness. Yet by decelerating quicker than your opponents you can always gain an advantage in the open floor as well as in short spaces on the court, which Harden has clearly been demonstrating all throughout his career.

The link is clear between an athlete’s ability to decelerate quickly and his or her eccentric strength (i.e. absorbing a large amount of force during the extension of the muscle, e.g. on the way down during a squat). So, anyone striving to gain an advantage on the basketball court would not want to miss out on an opportunity to build eccentric strength in their leg muscles. Of course that’s possible with weights but not always practical and effective in a team environment. On the contrary, basketball players of all sizes can train together and push themselves as much as they can handle by doing squats, lunges, RDLs and hip adduction/abduction on the kBox among other exercises, without having to adjust the weight on a barbell, its positioning in terms of height or worrying too much about technique.

Plus, the kBox will not only help you to improve your ability to stop before your opponent can even react, but it’s also great for improving your sprint speed and vertical jump, it’s widely used to prevent and rehab from injuries and it can help you get better at changing direction quickly, through lateral squats for example.

James Harden’s team, the Houston Rockets, are already kBox users and so are the Oklahoma City Thunder, the Los Angeles Lakers, the Chicago Bulls, the Boston Celtics and the Sacramento Kings in the NBA among other clubs in various pro leagues around the world. It seems that gradually the basketball world is embracing the kBox and how much it could add to your game, so don’t fall behind the rest of your competition by reacting too slowly. Control the pace.

/Bektur Savitahunov, Exxentric sales executive and basketball coach


ETSU Studies of kBox Inertial Setting and Force Characteristics

The choice of inertia and intensity are the main parameters affecting your workout in flywheel training. At the Coaches College event in December, two new studies from ETSU looking at this were presented. What do these add to or reinforce in the Flywheel Workout Zones? Here’s a walkthrough by Fredrik Correa.


  • A small increase in force can increase net impulse (and eccentric overload) much more.
  • Consistency in Force output within a set is high.
  • kBox is a suitable tool for eccentric overload.
  • Hence, these studies reinforce our previous beliefs.


In December 2016 at the last Coaches College, held annually in Johnston City, TN, two kBox studies were presented by the Center of Excellence for Sport Science and Coach Education at East Tennessee State University (ETSU). They started these projects after the summer, which are now gaining steam, and from what I’ve heard from Dr Kimi Sato at ETSU they are filled with ideas for coming projects too.

These first two projects I’d call descriptive since they look at different parameters acute during training at different settings. When presented to a new form of loading for resistance training the obvious question is ”will this be sufficient for adaptation?” and descriptive studies can tell us about that among other things.

To summarize their findings I’d say these two projects validated our previous beliefs and this will be a good platform for further research at ETSU.

Project titles were:




So basically, they wanted to look at force outputs during the #kBoxSquat and see how different inertia affected the outcomes and variability within sets and between users.

What they did

Ten subjects did:

Two sets of 13 reps of squats (3+10) on inertia 0.010, 0.025 and 0.050 where reps 2-9 of the test reps were analyzed.

Two minutes between sets and three minutes between inertia settings

They used force plates to register peak force, net impulse and positive to negative impulse ratio.


Increasing peak force with increasing inertia

  • My comment: as we know from the Force-Velocity curve, more inertia will result in a slow movement with the intensity unchanged and a slower contraction will increase the force production (See pic F-V relationship)

Peak force consistency over a set showed low variability between reps while variability between users was high.

  • My comment: High rep to rep consistency within a set but large variation between subjects and stronger subjects could elicit larger forces. This is also intent and intensity driven so even a stronger athletes could go ”gentle” as all kBox users already know. The benefit with this feature which we call ”variable resistance” is that you can get the load at a specific part of the ROM if you like. For example, you can start from a deep, low to medium intensity squat, just to get the full ROM and then explode at the end-range of the concentric phase. Other way around you can start with 100% at the bottom if the ECC-CON shift is something you want to focus on and as soon as you come up you stop pushing and just follow through in the last part of the concentric phase. The benefit is that you can target the whole ROM or the part where you want to improve and partly unload the rest of the ROM to increase the training volume on a specific part. For a weightlifter that could be improving the catch phase deep while not having to carry all the load through the whole ROM and save some work for the back or keep it the same while increasing the volume on the legs. This also allows for users differing in strength levels training together using the same settings which improves the logistics and the flow of the session, especially in a team setting.

Increasing net impulse with increasing inertia

  • My comment: impulse (F * t) increases as a result of the F-V curve described above. A slower speed will increase force production and with the slower speed and the same ROM the time t (Time under tension) will increase, as a result the product of these two obviously will increase a lot. Without knowing the physics, you realize this when you use the kBox, however it is good to understand that producing a higher force for a longer time increases the amount of work you put in a lot, increasing linear with the net impulse. This means 4 sets x 8 reps of kBoxSquats will be much more demanding in terms of rest and fatigue, if done with higher compared to low inertia, and you can’t just compare the number of reps to compare sessions. In the kMeter app you get a reading of the energy expenditure, which is a metric you can use to compare the amount of work between different settings and training modes.

Increasing positive to negative impulse ratio with increasing inertia

  • My comment: Higher overload with more inertia has been shown in previous studies (Gonzalo-Fernando 2016) even if it wasn’t exactly the same for both sexes. If you want to get a higher overload than higher inertia will give you higher total energy in the spinning flywheel at the end of the concentric phase. This higher rotational energy gives you more to play around with during the eccentric phase and also much easier to time it if you want the overload to come for example in the deep catch position. So if you are looking for eccentric overload in part of the ROM high inertia will give you more overload and it will be easier to target that specific range too.


Further on they discuss how a relative small increase in peak force results in a large increase in net impulse and P to N impulse ratio. This is interesting and as I discussed above putting in the same force or a slightly higher force but during much longer time (as a result of higher inertia) will result in much higher rotational energy and, as a result of that, higher eccentric overload (if you want that). As a side note I think their protocol put all load settings in the power spectrum with fairly high velocities and similar studies incorporating higher inertias > 0.1 kgm2 and fewer reps would be interesting. For example my average velocity is around 0.8 m/s when going max with one heavy flywheel (inertia 0.05 kgm2) so that’s quite far from absolut strength spectrum ( < 0.35 m/s), see pic for my own inertia vs average force and peak power curve.

One of their conclusions is that the kBox is a good tool for eccentric overloading, which can be achieved without a huge increase in peak force. Especially good for stronger athletes, which can create a larger momentum in the acceleration phase. I tend to agree with that fully and see this as one huge advantage for athletes and coaches starting to supplement their regular gravity-based training with flywheel training. Looking at the kBox in a wider perspective, the fact that you don’t have to carry all the load through an axial loading (either distributed through the harness or a belt) makes it very accessible for many team sport athletes with back problems that can’t do heavy barbell squats, common among ice hockey players for example. The logistics, instant feedback and variable resistance is of course beneficial for all athletes but also physiotherapists and personal trainers.

Practical implications and a few tips

  • Equal work?- consider the net impulse or total work in kJ for a set / session.
  • Lower inertia gives higher power, lower eccentric overload and less total work (less fatigue with the same volume of reps).
  • The kBox is a good tool for eccentric overload.
  • And lastly, I know ETSU has some interesting things in the pipeline so if you are interested in them continuing their kBox research give them a shout out and let them know you care about their work!

If you have any questions with regards to the choice of inertia, just drop me an email or check out our courses.

Happy DOMS!

/Fredrik Correa, Head of Research & Development


“Almost Impossible to Achieve in Traditional Weight Room Methodology”

PhD and kBox pioneer Mike Young reveals some of his key flywheel training strategies and more for UC Berkeley strength and conditioning coach Joel Smith in his latest podcast. Fredrik Correa thinks you should listen in.

In the last episode of the Just Fly Performance Podcast, coach Joel Smith is having the US kBox pioneer Mike Young on. Mike is well known for his work at his facility Athletic Lab and for his work in MLS, and as a well traveled speaker at high level conferences and workshops world-wide. We were much fortunate to have him at the Exxentric Summit 2016 (you can download that lecture here).

On this episode, Mike talks about developing sprint and speed ability in team sports athletes. The question of how much you should invest into working on mechanics with non-sprinters is interesting and Mike has some great insights in this area. Further, he discusses if there are differences in cuing between sprinters and non-sprinters.

Discussing the kBox

To finish it he gives his take on velocity based training and (from 38:30) the kBox. Mike lets us know how he sees the kBox in a performance setting and what they use it for in power and strength development. We also get to know how he uses it weekly with his track and field group.

Being a long-time advocate of isometric and eccentric training Mike explains that he now appreciates the safety and logistics of doing this with the kBox as compared to traditional methods.

“For many years i had to come up with some very creative and borderline dangerous things to kind of really press the pedal to the metal. I think the kBox provides a very safe alternative to a lot of the things that I was doing, and its much logistically easier.”

They reach overload of up to 175% with elite athletes, and doing that with regular weights is both complicated, time consuming and somewhat dangerous in my view.

“We’ve seen #eccentricoverload depending on the movement velocity and the range of motion in the 150 to 175% range, which is really almost impossible to achieve in traditional weight room methodology. So, I love the kBox. It’s been a great tool for us.”

With team sport athletes they do more of metabolic and hypertrophic training and the eccentric overload, being excellent for injury prevention, has made them replace most of the Nordic hamstring work with overloaded RDLs on the kBox.

Thanks for Sharing

I hope you’ll enjoy this podcast as much as I did. There are plenty of performance podcasts out there and you can’t really listen to them all, but this is a good one that I can highly recommend you make some time for. Thanks Mike and Joel for sharing!

Happy DOMS!

/Fredrik Correa, Head of Research & Development

PS For more podcasts relating to flywheel training, check out the media page.