Releasing New Product Line With Limited Launch Offer

It is with great excitement that we now announce a new family of flywheel training devices.

Two of the devices are brand new, namely the affordable kBox4 Active and the kPulley, for horizontal movements. In addition, we introduce important updates to our existing products, the kBox4 Lite, the kBox4 Pro and the kMeter.

Versatility and value for money has never been greater than now, with Exxentric’s new family of flywheel training solutions.

New Devices

kBox4 Active

The kBox Active is our new and robust entry-level device. Perfect for serious home users, group class training and practitioners of sports at all levels.

The form factor is the same as the kBox4 Lite, but the inertia range is more limited and the device is made of steel instead of aluminium. It is coated with an attractive new bronze colour. The kMeter can be purchased as an accessory.

We are very pleased to offer a highly efficient strength training device at a very attractive price point, allowing even more users to enjoy the benefits of flywheel training. Learn more.


The kPulley is our brand new device optimised for horizontal movements. It is based on the Exxentric flywheel training solution using a straight shaft.

Facilitating a completely new category of horizontal exercises for the upper body, the kPulley is the optimal solution for anyone looking to improve their strength through rotational and pull exercises, but also core and lower limb exercises. With its versatile wall mounted design, the height of the attachment point can be adjusted between around 40 cm and up to 220 cm.

Like the kBox4 Pro and Lite, the new kPulley also comes with the kMeter II feedback system built-in and it is coated in the classic Exxentric brown colour.

With the kPulley addition, a full body strength workout is now available with the Exxentric flywheel training solutions. Learn more.

Updated Devices

kBox4 Pro

Widely appreciated by sports teams, pro physiotherapists and many others all over the world, the kBox4 Pro, is our most renowned and premium model.

Already very feature rich, the Pro model has now been updated with our new Floor Attachment Kit (see below), in addition to a number of continuous improvements applied since its original launch. Most importantly, starting today the kBox4 Pro will come pre-fitted with the new kMeter II feedback system, without extra charge, effectively lowering the purchase price for a fully equipped professional system.

The kBox4 Pro remains the top choice for professional users looking for the full width of options for maximum performance. Learn more.

kBox4 Lite

With today’s release, the kBox4 Lite is greatly improved for professional users in need of a smaller, highly portable device.

Like the kBox4 Pro model, the kBox4 Lite will also include a built-in kMeter II. We have also managed to make the Lite even lighter, further improving its portability, while at the same time doubling the potential inertia range. The kBox4 Lite can now hold up to four flywheels, just as its big brother. The automatic belt retract solution from the kBox4 Pro is now also standard, as is the option to add Foot Blocks. In spite of all the improvements, the cost of the Lite remains unchanged.

The kBox4 Lite is now, even more, the ideal solution for users such as travelling athletes, rehab and fitness studios. Learn more.

Further Updates

kMeter II

The kMeter feedback system has been completely rebuilt, and now offers an improved user experience, including sleep mode with activation via the app, so no more on-off switch, and improved battery life. In addition, as of today all kBox4 Pro, kBox4 Lite and kPulley units will include a built-in kMeter II at no extra cost.

Head Harness

This new accessory is ideal for all of those wanting to incorporate flywheel training for their neck strength, making Exxentric’s list of accessories even more complete.

Floor Attachment Kit

As an update to all our kBox4 devices, a new Floor Attachment Kit will now be included with all kBox4 systems, resolving a need communicated by many customers. This will help facilitate simple attachment to a facility’s floor, to stabilise it as well as to improve lateral exercises. The kit is also available for older versions of the kBox4.

Launch Offer

We have always strived to keep offering excellence in product quality at market leading prices, and we are happy to be able to further this goal also with this release.


The price for the new entry-level kBox4 Active is only € 1,410 (US$ 1,585) for a Starter System. The new kPulley comes at a market leading € 1,750 (US$ 1,955), also for a Starter System.

The prices for the upgraded kBox4 Lite and kBox4 Pro remain, with Starter Systems at € 2,300 (US$ 2,575) and € 2,990 (US$ 3,345), respectively, including all new features.

As usual, our prices exclude shipping and any local taxes.


The upgraded kBox4 Pro is already available in stock for immediate shipping.

The upgraded kBox4 Lite and the new models kBox4 Active and kPulley are currently in final production and are expected to start shipping in June.

Starting today, we are accepting orders for the new product line. The products will be supplied in the order we receive confirmed orders. As we cannot anticipate the full demand for the new products, it is a good idea to order soon to avoid any unnecessary waiting time.

Limited Launch Offer

As a sign of our appreciation for your patience with our longer than usual shipping time of the kBox4 Active, kPulley and kBox4 Lite, we’re offering a 10% discount on systems including those products. This limited launch offer is applicable for orders that are confirmed and paid before May 31st. Don’t miss out!


We want to thank all of our partners and users, now in 60 countries, that have been involved since the beginning. We will continue to do everything to ensure all of you have the best possible Exxentric experience!

Interested in learning more about the new product line? Contact us or your Official Reseller to get a quote or the full price list today.

/Erik LindbergErik Lindberg, CEO

How to Choose Your Flywheel Training Device

Are you thinking about investing in a flywheel training system, but unsure of which device to choose? Here are the 10 key things to look for to secure the ultimate training experience.


  • Range of motion is important both in lower and upper body exercises
  • Consider getting devices for both horizontal and vertical movements
  • Low friction is key for eccentric load and overload
  • Inertia range is important and even weaker subjects might need high inertia in specific situations.
  • Low weight is important for the traveling athlete or coach
  • A feedback system is crucial for motivation, monitoring and follow up.
  • Stackable design is beneficial for multi-system users like gyms and performance facilities
  • The key accessories you need should be included
  • The community that comes with the brand you select can be a powerful ally
  • Service, customer support, warranty is easy to forget, so check beforehand and ask around

A flywheel device is probably the best purchase you can make if you already have a decent setup. Allowing for eccentric overload and a resistance type with proven robust and fast gains in strength, that also translates into performance, is key for many consumers in the athletic field. The safety, the relatively short and steep learning curve and ergonomy is great in physiotherapy, training seniors or developing athletes.

The efficacy and higher return on invested time is a game changer when it comes to health and fitness, both for gym-goers and home users. The easy part is to realize that a flywheel training device can solve many of the problems or obstacles you see in training.

However, the hard part is how to choose which device to get.

To help you I’ve compiled a list of 10 features that you should look for, as a buyers’ guide to use when comparing your alternatives. Looking “under the hood” can be difficult if you are testing a device. You might come across a nice looking design with a fairly reasonable price and the training feels good on your first attempt but what is there to consider before committing to a purchase? Here are a few factors worth considering if you want to end up being fulfilled by the device you get.

As you will notice, I don’t bring up design or price since this is personal and depends on your taste and size of your wallet. If you aren’t sure about the price, look around for other devices to get an understanding of the different price points. Most serious producers have their price listed on their website.

1. Range of motion

A range of motion is something that is easy to miss, even if you test the device. In this aspect, you have to consider both the highest top position and the lowest bottom position. Let’s start with the top position. In a demo, you might be shown a squat and then try a squat and some RDLs and you don’t realize the range of motion might be restricted to the waist area, so all upper body exercises are out of the question. Missing out on curls, pulls, rows with a low top position can be a huge drawback when you want to incorporate flywheel training into your programming.

When it comes to bottom position, a few devices have the shaft positioned on top of the foot placement area, which means these devices lose a lot of depth in the squat if you compare with a device where the shaft is placed underneath the platform for example. If you want to be doing squats lower than 90 degrees I suggest you start looking at the units with shaft placement under the platform. You can also take a look at the pulley that the device uses for connection to the belt, harness or grip. Some of these pulleys are rather big and also take away a lot of the range of motion in the depth. Make sure you can squat without the pulley interfering with your legs or your depth before you go ahead.


To me this is a rather easy question to answer since this is not a conflict. There are many good vertically orientated exercises (pulls, squats, deadlifts, curls) and while there may not be as many horizontally orientated exercises there are still some very important ones such as rotations and shoulder exercises. So if you like flywheel training you might consider getting both types of devices. However, it’s worth noting that overload studies haven’t been done on any horizontal devices due to the higher level of difficulty when creating overload with them. The conic variations are also high speed – low force so they might be good for some explosive movements and metabolic training but maybe not as good for traditional strength. You are also limited since the limiting power output is how much force you can generate or absorb without being pulled into the device (compare lat pull if you can’t fixate your legs, at BW lifts you start lifting yourself instead and not the weight). Decide which exercises and type of load is most important for you and go with that device to start with. If you like flywheel training consider getting the other device too.

3. Friction

This is something most people don’t realize is important, which is also true for some of the manufacturers, unfortunately. Friction creates resistance, which means it will add load in the concentric phase and decrease load in the eccentric phase. A high degree of friction will make the eccentric action underloaded. Even a small increase in friction can have an impact on your training and adaptation.

For example, 5% friction means that 5% of the power output will become heat. Then on the way down another 5% disappears, so in the end, you are only absorbing about 90% of the load or energy you put in during the concentric phase. With 15% friction, the eccentric phase is underloaded with about 30%. Then one of the main reasons for using a flywheel device is eliminated.

Friction may accumulate due to the quality of the device’s ball bearings or the drive belt/wire used. A very stiff belt or wire will create resistance since it will resist being rolled up more. To test the bearings, disconnect the belt or wire around the shaft, attach a flywheel and start spinning it. If the speed is very gradually reduced and it continues to rotate at a very low speed at the end, the level of friction is fairly low. A hard and distinct stop at the end probably means there is significant friction.

Another issue around friction is the data assessment from the training. Most devices measure rotation, so you only see what energy goes into and out of the flywheel rotation. This means friction will make the concentric workload look smaller (more work needed for same acceleration) and the eccentric workload will look bigger than it actually is (less work needed to decelerate the flywheel since friction ‘helps’).

4. Inertia range

Training in the strength-power spectrum for a normal user doing leg exercises might not require a very wide range of inertia. However, when working smaller muscle groups, doing unilateral drills or for special populations like seniors, a really low inertia can be necessary. On the other side of the spectrum for rehab and stronger athletes, a much higher inertia is needed for heavy slow resistance training in tendinopathies or for max strength and overload in regular RT.

If you just can fit an additional flywheel that is good and you can order that one when you need it. However, in some devices, the possibility to change to another flywheel or add multiple flywheels might not exist. Check the available inertia levels on the device beforehand in order not to limit your use of the device.

5. Weight and dimensions

The material, density and design set the weight, which is an obvious restriction if you want a device that you can move around or bring with you. When it comes to storage, some devices could also be stackable which means they require very little space when they are not being used. A set of multiple systems with heavy devices that aren’t stackable would end up demanding a lot of permanent space in a gym, basically its own room, while a lighter, stackable device can be moved around and brought out when needed. And the range when it comes to weight is huge, some could be as light as 12 kg (26 lbs) while others with the same basic functionality could weight over 150 kg (330 lbs). Furthermore, a heavy device may also restrict the possibility of support, where a light device can be returned and repaired more easily. The heavier device would most likely call for an on-sight technician. Ask beforehand how the manufacturer deals with these issues, so you avoid any surprises later.

6. Feedback system

A good feedback system can be a very simple tool just showing power in-real time or more advanced functions and databases, depending on what you need. For all subjects, patients, athletes, weekend warriors alike, the impact on motivation and intensity is huge with a functioning feedback system. However, don’t get too hypnotized with all the features and functions you are being shown and be sure to decide first which metrics are important for you and what you’ll actually use the app for and with who.

What you have to consider is the additional cost of the feedback system. Some require being run on a laptop for example, which that might add cost and complexity to your system compared to an app for a tablet or smartphone. Some feedback systems may lock you up with subscriptions and additional costs, so this can also be verified prior committing. Some systems still use cables, which is beneficial in environments with a lot of interference but in all other cases, it’s probably more problematic.

7. Ease of Use

When being demonstrated, a device it always looks very simple but do not fall for the demo tricks, you should try it for yourself and ask to test different exercises. This will give you a chance to observe the setup and transitions on this particular device (i.e. changing flywheels, the range of motion or switching between accessories such as grips, bars or harnesses and etc). The operation is very important in the day to day work.

Some devices have the flywheels fixed with a screw and some with a quick lock. With everyday use, you can understand that you will experience a big difference between those setups. Having to lean down to reach a rope to adjust the height might not be a problem during a demo but you might realize very soon that this is troublesome in the daily practice and some of your users might find it really hard to do by themselves too. Stackability is a good feature for anyone with multiple systems, which was also brought up under ‘Weight and Dimensions’ above.

Another issue is noise. Many demos are being done in noisy environments like exhibitions and you might not realize that some of these devices are almost silent and some quite noisy until you get them into your own facility.

8. Accessories

Most manufacturers offer their own accessories. However, if you already own a favourite bar or grip that you would prefer to continue using with your new flywheel training device, you should also check the device’s compatibility with foreign accessories, so that you aren’t restricted only to the manufacturer’s items. Since the accessories are the interface between the device and the user, they can affect the overall feeling to a large extent. A good quality bar, grip or harness that fits well can all be important factors when it comes to justifying your decision to purchase the device.

If you deem it critical to be able to purchase everything simultaneously, then make sure the key accessories you need are included with the device you’re considering before you complete the order. See if you can also spot any sneaky business strategies from the manufacturer, who might try to bring down the price point on the device itself while adding quite a bit of margin on the accessories instead. So compare prices versus similar accessories with other suppliers if you don’t want to end up with a higher total cost for a lower cost device.

9. Community

The community is important if you want to be an early adopter and innovator in your field. The relationship between the user and trainer experience from other professionals in the field can be a great asset. How is the manufacturer’s network locally, regionally and globally? And are there any other professionals you can discuss training within that community? Since all devices and their feedback software are slightly different you probably need to find users of your particular device to really benefit from their experience.

10. Service & customer support

Some manufacturers may be local but offer their product globally, meaning they might not be able to efficiently help you due to time zone differences or language proficiency with customer support. First, take a glance at the material they publish online, is there enough there to get you started? If not, contact them and see if they are able to provide you with more or willing to discuss more educational material so you don’t end up disappointed. Existing customers are the best judges when it comes to their level of customer support. If possible reach out to an existing customer and ask about how their experience has been. If you can’t find a user for a specific device, are you sure you want to be the first?

So I hope this checklist will bring you confidence when you are looking to invest in your first flywheel training device. Now get out there and make a good deal and enjoy the benefits of flywheel training. Whatever product you do end up choosing, make sure to stay tuned here for the latest in flywheel training research and practises, all flywheelers are welcome! Remember, as much as you can be restricted by a device not offering the functions you need, if you don’t keep up with the latest scientific findings, you will be restricted by your knowledge when utilizing your new tool.

Happy DOMS!

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

For further reading on the scientific support for flywheel training, look here.

FIBO Nominates the kBox for Performance Award

As one of the industry’s largest events of the year is just around the corner, we have been sitting on some very exciting news that now we are ready to share with all of you!

This year at FIBO, the largest trade show for fitness, wellness and health in Cologne, Germany we will not only be exhibiting alongside one of our German resellers Pullsh but with great pleasure, we are excited to announce that we have also been nominated for the Innovation & Trend Awards!

As some of you might know already, these awards are often referred to as the industry’s “Oscars,” and are hosted by FIBO in cooperation with the German Industry Association of Fitness and Health (DIFG). With 108 submissions that were divided into five different categories; Digital Fitness, Health / Prevention, Lifestyle / Life Balance / Wellness, Performance / Capabilities and Start-up, we are honoured to be selected to compete in the performance category.

On April 11th in front of an audience of 400 leading industry representatives at the European Health and Fitness Forum, the winners from each category will be announced.

Each year over 150,000 global industry leaders in the pursuit of the latest and greatest trends and innovations attend the largest international trade show for fitness, wellness and health in Cologne, Germany at the Exhibition Centre Cologne from April 12th to 15th.

Will you be attending FIBO this year? Make sure to swing booth 7/A01 to try the #kBox4 and meet flywheel training experts Alex Bonell and Felix Roßkopf. If you are interested in a partnership with Exxentric, please contact us to book a meeting with our Head of Sales & Marketing Johan A Larsson or Business Development Manager Anton Villberg at FIBO.

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.


Flywheel vs Weights for Eccentric Overload in Strong Athletes

If you have seen any athlete do eccentric overloaded squats on the kBox you will realize that there aren’t any research papers covering that type of training. Question is, do these targeted eccentric loads provide a sufficient, or even greater, stimulus than weights in elite athletes?

To bring some clarity into this we asked a national champion weightlifter to squat in our gym and compare the eccentric load in the deep portion with a barbell vs the kBox to see what happened. Which modality generated the highest eccentric loads?

Key points:

  • kBox provides a high eccentric load and eccentric overload even for really strong athletes and good barbell squatters, even more so than weights.
  • Eccentric overload means eliciting a higher force (in that motion or angle) eccentrically than you can elicit during a concentric movement. For a whole lift this is > 1 RM or in a part of a lift ECC force > CON force in that range.
  • It’s not only about the type of exercise, the amount sets, reps or the inertia you use. It’s about HOW you do it.
  • Read up on methods for eccentric overload on the kBox.
  • How to use the kMeter for assessing eccentric overload. Avoid the pitfalls.

Eccentric Overload and the kBox

I’ve written about this before so if you want to skip the rant and dig into the results skip this section. The physiological background to all of this eccentric training is mainly that the muscle can produce higher forces during an eccentric action versus a concentric one. By using a weight for resistance, the load in the eccentric phase is set by your concentric strength. You can only lift weights up to your concentric 1 RM and with a 30-50% stronger eccentric action you aren’t working as close to your eccentric max as your concentric max using gravity as resistance.

The term ‘Eccentric training’ is used for many things and the very general and vague description “training with focus on the eccentric action” can translate into many different things, with the most common one being the super slow eccentrics you see from time to time. Other things can be more isolated eccentric actions like when we see with the Nordic hamstrings exercise (NHE) for example. NHE has been proven to elicit both improvements in neuromuscular strength, trigger structural adaptations and to reduce the incidence and re-occurrence of hamstring injuries.

When we talk about eccentric overload we mean loads beyond your max concentric strength (> 1 RM). However, strength is also specific to the exercise, speed and range of motion. So the overload can also target a certain part of the range of motion, being overall within a 1 RM load but still considered as eccentric overload. On the kBox for example you can generate max force in the concentric phase and put a certain amount of rotational energy into the flywheel. By absorbing it evenly over the eccentric portion you get a 1:1 relationship CON:ECC. You can also delay the eccentric action and absorb all that energy in for example the deep portion, but then you have to do it in a much shorter period of time. Since Power is Force times Velocity, you can also say Power is Force times Distance divided by Time. If you accelerate or decelerate a load in half the time, you would have to double the power. So without doing 2-1, using spotters etcetera, you can easily and safely overload exactly where you want in the range of motion.

Pilot Project: National Weightlifter Using kBox for Overload

The backstory here is that we came in contact with the former Swedish National champion in WL -77 kg. He trained two sessions a day, 6 days a week. He was a student back then who was about to get his degree and start working so he realized he would only make it to the gym once a day from that day forward. Being a former champ and now ranked #2 he of course wanted not only to use the kBox as a replacement but also to improve his performance and catapult back into the top position again. He has been using the kBox at home since then and we have been lucky to be able to bring him in to Exxentric HQ from time to time to do a few test sessions. One of the things we wanted to test was to see how much eccentric overload he can get by using the kBox. About 6 months ago we compared heavy barbell (BB) squats with normal kBox Squats 1:1 and those were fairly similar. We ran out of time and he ran out of juice that day so this latest session was focused on maximal eccentric load. To do so we added more inertia and a delayed eccentric action to make him work harder in the deep portion of the eccentric phase.

Set up

Aim: compare eccentric peak forces between heavy barbell squat and high inertia kBox squat with and without delayed eccentric action (i.e overload).

Subject: National elite male weightlifter, bodyweight 80 kg (176 lbs), back squat 1 RM 195kg/430 lbs.

Measurements: two Pasco force plates, 250 Hz. MuscleLab. Video.

Barbell load: 82%, 88%, 92% of 1RM for two maximal reps (ie maximal intent and velocity in concentric and eccentric phase).

kBox 1:1 load: 0.100, 0.150, 0.200 kgm²

kBox overload load: 2+2 reps of kBox squats with inertia 0.200, 0.240 and 0.280 kgm² with delayed eccentric action. As a note if you look at all flywheel studies published until today max inertia used is around 0.110 kgm². This means we used x2.5 more than the inertia seen published in the literature.

Our subject Erik was told to delay the eccentric break on the kBox as long as he felt he could, without being pulled into the hole. The concentric actions were maximal on both exercises.

RESULTS Heavy squats vs 1:1 kBox

When looking at peak forces we wanted to look at the deep portion of the squat so the peak force value is the highest value in the range 60 degrees (ECC) – 45 degrees (bottom) – 60 degrees (CON), ie the turn.

From the earlier session you can see in the three first columns vs kBox 1:1 that peak forces increase with increased BB load. However, the eccentric load (in terms of peak force) on the kBox doesn’t increase as much with increased inertia in the 1:1 setting. Due to our subject getting tired we don’t know what numbers a maxed out inertia would look.

To get a closer look at this and really stress the overload we continued this at a later session with two higher inertia settings, 0.240 and 0.280 kgm², and with the delayed eccentric action. Now he is increasing the load quite a bit in the deep portion of the squat both looking at the best rep and the average force between the two reps. In the table you can see the comparison vs the “best” barbell set, 92% of 1 RM. A win for the kBox with +14% peak force in best rep and +11% in the average for two reps.


From this n=1 trial we can’t draw any strong conclusions or present “new facts”, you don’t need to be a scientist to know that. However, since no study has looked at elite squatters and compared their BB squat and flywheel squat we have nowhere else to get any info at all. So what did this experiment show? Now we have an indication that the kBox Squat 1:1 provides a fairly high eccentric load without “trying” to stress that specific load, this is a regular CON-ECC movement. However, when increasing inertia and trying more actively to force an overload we get quite high overload vs weights even with an elite weightlifter that is really an expert in training with high loads on the barbell. Even for him you can see the practical differences in the video. With the heavy barbell squats we have a spotter but on the kBox he trains unsupported and he is, as I told you earlier, doing this at home in his apartment two or three times a week during some cycles.

I’d suggest that the average athlete and barbell lifter would get an even higher overload vs their maximal squat since they have a limited technique, strength and experience in the barbell squat (at least vs a elite weightlifter). This also tells us that we can’t just focus on sets, reps or inertia but it is also about HOW the exercise is performed. By delaying the eccentric action you can target this area of the range of motion. In the same way you can target the end range power by absorbing the flywheel energy very early in the ECC action. So, it’s not only about WHAT you do but HOW you do it. Let the kMeter assist you and think about what effect you want and where you want your athlete to be loaded. All squats aren’t equal, especially not on the kBox.

Happy DOMS

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

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


Launching Online Courses in Flywheel Training

The world is a big place and unfortunately we can’t be everywhere at once. To make knowledge about the kBox and flywheel training more accessible, we are now launching our first online courses at Exxentric Academy. Fredrik Correa explains:

Key points:

  • Courses available for potential customers as well as existing users
  • All are currently free of charge, open 24/7
  • Requests for custom courses welcome!

Nothing beats attending a good course in real life. Meeting people, discussing and mixing theory with practice. We have been traveling around the world to do flywheel training introductory courses of all kinds – and we have loved it. I have personally learned a lot from meeting people interested in physical training engaged in different ways on the rehab–fitness–performance spectrum from different sports and settings.

Attending a course is of course a great way to get started with your flywheel training but it is also a way to evaluate the tool and the training before committing to a purchase. So of course, spreading knowledge is vital for us at Exxentric. Why would we support 10+ research projects if that wasn’t the case?

However, with the kBox now in 45 countries, we need to add new ways of sharing knowledge. Writing articles or tweets is good for Q&A, and conducting 1 on 1 courses over Skype is still an important tool for us. But we wanted to start making the knowledge in our field even more accessible. That’s why we are now launching an online learning platform.

Available Online Courses

Today, you can find our first online courses at Exxentric Academy. Like always, we are starting small but hope to develop this depending on your needs. Courses we added to the platform so far include:

  • kBox4 demo [English & Swedish]
  • kBox4 getting started intro (for new customers) [English]
  • kMeter intro course [English & Swedish]
  • Lecture on flywheel training for physios [Swedish]

All of the currently available material is offered for free, so take a look and give us your feedback. It’s far from perfect and you have to be able to withstand a fair amount of ‘Swenglish’ to get through this but I hope it will help you anyway.

Future Online Courses

There are of course a bunch of courses that could be done but instead of deciding what is important for you we hope that you will tell us. We can talk about programing, different ways to load, how to use the kMeter, ways to make your training more specific to your needs. Everything from general to very specific is on the table. If you ask for it and we got the time, we are ready to do it.

1 on 1 Intros

I just want to highlight the possibility for you to get started with your flywheel training over a 1 on 1 conversation through Skype or Google Hangouts. This can be a great way for a dedicated home user upgrading his gym with a kBox to get started and getting ROI from day 1 on your investment. Reach out to us for pricing if you are interested. There are also experienced coaches all over the world using the kBox that might be able to coach you online for more regular sessions and follow-ups. Maybe we can connect you if you are interested.

Real Life Courses

We will of course still do our standard courses in real life when people are interested, just like today. Reach out to me if you want to host a course at your facility or if you have any feedback for us regarding education.

Happy DOMS!

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

BJ Gaddour’s Best kBox Training Programs

As many of you already noticed, BJ Gaddour has gone on a kBox frenzy. Here, Fredrik Correa shares a few of his videos to inspire your personal fitness routine.

Since this summer, the former Athletic Director of Men’s Health magazine, BJ Gaddour, creator of The Daily BJ, has shared a ton of quick and intense programs to his +200k followers with the kBox as as a central piece of equipment.

His programs are perfect for a busy schedule and I wanted to highlight some of them here, both to return the favor and to show the kBox being used in a home gym setting as opposed to most of the other media we share.

Maybe a few of these programs will fit as recurring workouts for you, or maybe you just want to take one or a few of these drills and put them into your own existing program. As BJ points out, just as you can do lots of traditional free weight exercises on the kBox for increased effect and efficiency, most of these programs can be done with traditional equipment as well.

Use this for inspiration! Here we go:

Upper body workouts

Lets start with this post focusing on upper body:

#FlexFriday 💪with some straight Bro-J Gaddour arms, shoulders, and back blasting! I’m using the @go_exxentric #Kbox4 and @concept2inc #SkiErg but just focus on the exercises/movement patterns and use whatever equipment you have access to for a precious pump to kick off the weekend: 1. Single-Arm Lateral Raises @ 3 sets of 8 reps/side 2. Triceps Pushdowns @ 3 sets max reps/distance in a minute 3. Single-Arm Row @ 3 sets of 10 reps/side 4. Overhead Triceps Extensions @ 3 sets max reps/distance in a minute 5. Single-Arm Concentration Curl @ 3 sets of 8 reps/side 6. Reverse-Grip Bent-Over Row @ 5 sets of 15 reps 7. Reverse Fly @ 5 sets max reps/distance in a minute 8. Split Kneeling Overhead Press @ 5 sets of 15 reps 9. Straight-Arm Lat Pulldown @ 5 sets max reps/distance in a minute 10. High Pull @ 5 sets of 15 reps #AskYourGymToBuyThis #TheDailyBJ #NotAPornSite #AllBJNoBS #Back #Arms #Shoulders #BroJGaddour #AllBro #UpperBody #UpperBodyWorkout #Bodybuilding #Muscle #TGIF #BJGaddour #💪

Ett inlägg delat av BJ Gaddour (@bjgaddour)

Another one focusing on arms and deltoids:

💪ARMS, DELTS, & CARDIO! Here was the flow of a recent upper body and cardio workout. I got a savage heart and muscle pump. As always, modify with whatever equiment you have access to and apply the principles for dem gainz. CIRCUIT 1 1a. @go_exxentric #Kbox4 rope hammer curl 1b. #Kbox4 overhead rope triceps extension 1c. Reverse fly on @concept2inc #SkiErg @ max distance in 2 minutes CIRCUIT 2 2a. #Kbox4 rope front raise 2b. #Kbox4 rope upright row 2c. #Kbox4 rope bent-over row 2d. Straight-arm lat pulldown on @concept2inc #SkiErg @ max distance in 2 minutes CIRCUIT 3 3a/b. Side-lying dumbbell lateral raise L/R 3c/d. Standing band lateral raise L/R FINISHER 4a. Blood-flow restriction triceps pushdown 4b. Blood-flow restriction lying biceps curl Join (direct link in my bio) to access my exact daily workouts with sets, reps, rest, etc. #TheDailyBJ #NotAPornSite #AllBJNoBS #Arms #Delts #Cardio #MetabolicBodybuilding #Gainz #Bodybuilding #Muscle #ArmsWorkout #Biceps #Triceps #Shoulders #EccentricTraining

Ett inlägg delat av BJ Gaddour (@bjgaddour)

Lower body workouts

Working them legs:

LOWER BODY WERK! Wearing my @pedestalfootwear barefoot training socks to maximize the lower body gainz. As always, modify with whatever equipment you have access to and focus on the movement patterns and principles: 1. Front-Foot-Elevated Split Squats 2. 1-Leg Leg Curls 3. 1-Leg Hip Flexions 4. Constant-Tension Fingertip-Assisted Russian Leg Curls Moves 1-3 are using the @go_exxentric #Kbox4 fly wheel trainer for eccentric overload- the faster you go up, the faster it comes back down. I did 6 sets of 20 reps/side for move 1 and 3 sets of 20 reps/side for moves 2 and 3. Move 4 uses the #SpeedBot floor glute-ham developer but you can modify by hooking your feet into a lat pulldown seat or having a partner hold your feet down. Keep constant tension on those hammies by staying in the bottom half of the range of motion, using only as much fingertip assistance as needed to execute the reps. I did 3 sets of max reps to finish the workout. I post my exact daily workout at (direct link in my bio) under THE DAILY BJ category. Check it out! #TheDailyBJ #NotAPornSite #AllBJNoBS #Legs #LegDay #TheHamstringGuy #EccentricTraining #RussianLegCurls #NordicCurls #LegCurls #BJGaddour #Gainz

Ett inlägg delat av BJ Gaddour (@bjgaddour)

Two of my favorite drills on the kBox, Rows and RDLs:

💪TRIPLE BACK STACK!🍑One of my favorite ways to hit any muscle group is stacking 3-competitive moves back to back to back. It’s a great way to get a lot of work done in a very short period of time, extend time under tension, and create massive muscles pumps and metabolic stress to spur growth. Plus, you can accomplish all of this using lighter loads which is great for longevity. Here are 3 sample triple back stacks using different equipment that will also hammer your glutes and hamstrings. They incorporate a “mechanical drop set” where you start with a weaker position and move to a stronger position as you fatigue while using the same load. 1. Barbell Overhand-Grip Bent-Over Row/Underhand-Grip Bent-Over Row/Hip-Hinge 2. Dumbbell Overhand-Grip Bent-Over Row/Hammer-Grip Bent-Over Row/Hip-Hinge 3. @go_exxentric #KBox4 Flywheel Trainer Overhand-Grip Bent-Over Row/Underhand-Grip Bent-Over Row/Hip-Hinge I use a mini-band wrapped above the knees on setups 1 and 3 to increase hip activation and put the lower back in a more stable position. I block my feet together on setup 2 so the dumbbells don’t hit my thighs and to increase the range of motion through my hips and hamstrings. To see the full instructional video with sets, reps, rest, etc. visit (direct link in my bio) under the GAINZ category. #TheDailyBJ #NotAPornSite #AllBJNoBS #Gainz #Back #BackWorkout #BackCircuit #DropSet #MechanicalDropSet #Bodybuilding #MetabolicBodybuilding #BJGaddour #TransformationTuesday #Glutes #Hamstrings

Ett inlägg delat av BJ Gaddour (@bjgaddour)

This Zercher variation rightfully stimulates a lot of the core and arms since you have to stiffen up the whole chain from the bar to the foot to be able to produce force:

EXERCISE ORDER ON LEG DAY FOR MAX GAINZ! Most trainees will do the heavier bilateral moves first in a lower body workout. I used to do it that way too when strength and load was more of a priority. But now that performance, longevity and muscle gain is my main focus, my approach is quite different. I do unilateral moves first to optimize muscle activation, joint positioning, and mobility. By the time I get to the heavier bilateral work, my nervous system is primed, my joints are lubricated, and my muscles are moist. With this approach over the last year or so I’ve never had better leg days. I get precious, pain-free pumps and my recovery is dramatically faster. Here was the exercise order at a recent leg day sesh: Circuit 1: 10 reps each 1a. Single-leg band hip thrust- left side 1b. Single-leg band hip thrust- right side 1c. Single-leg, single-arm hip-hinge- left side 1d. Single-leg, single-arm hip-hinge- right side Circuit 2: 10 reps each 2a. Zercher Bulgarian split squats- left side 2b. Zercher Bulgarian split squats- right side 2c. Russian leg curls Circuit 3: High reps (20-30+) 3a. Constant tension Bulgarian split squats- left side 3b. Constant tension Bulgarian split squats- right side 3c. Mini-band (hip circle from @mbslingshot) hip-hinges I’m using the @the_hip_thruster for 1a and b, the @go_exxentric #KBox4 fly wheel trainer for 1c, 1d, 2a, 2b, and 3c which provides eccentric overload (the faster you pull up, the faster it goes back down), and the floor glute-ham developer for 2c is from #SpeedBot. But use whatever equipment you have access. I love finishing with high-rep bodyweight moves, especially if I did that same move earlier in the workout with heavier loads. Start re-thinking the traditional approach to #LegDay if you’re looking for better long-term #gainz. I post my exact daily workouts from the week before complete with sets, reps, rest, etc. at (direct link in my bio). Check them out! #TheDailyBJ #NotAPornSite #AllBJNoBS #Legs #Quads #Glutes #Hamstrings #Fitness #Fitspo #Fitspiration #ReturnOfTheMack #Bodybuilding #MetabolicBodybuilding #BJGaddour #Circuit #CircuitTraining #CircuitWorkout

Ett inlägg delat av BJ Gaddour (@bjgaddour)

Have fun!

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