Per-Olof Åstrand Remembered:
My First Inspiration for Applied Sport Science

It was with great sadness that we noted the recent passing of legendary physiologist, professor Per-Olof Åstrand of the Karolinska Institute in Stockholm, one of the pioneers of modern exercise physiology.

Our co-founder Mårten Fredriksson, an olympic coach focusing on strength and conditioning for ice hockey, had the privilege of meeting professor Åstrand many times, developing a warm friendship. Here are his personal memories.

Per-Olof Åstrand and Mårten FredrikssonI met P-O Åstrand for the first time during my first semester at the coaching program at the Swedish School of Sport and Health Science (GIH). It was the autumn 1998 and he held a lecture about the emergence of exercise physiology from the 1960s onwards. I remember him mentioning that in the mid 1960s and early 70s…

  • human skeletal muscle biopsy had just been introduced
  • the first studies related to diet and physical performance were yet to be published
  • there were no discussions of fiber types or the effects of training and deconditioning on the enzyme systems, capillary density, and myoglobin concentration
  • there where no papers dealing with the relationships among exercise, fitness or osteoporosis
  • the terms anabolic steroids and strength training were not combined
  • the first report of blood doping appeared in 1972
  • etcetera

The first “lecture” I held myself in P-O’s presence was when the ice hockey team Toronto Maple Leafs visited Stockholm for a training camp and their strength & conditioning staff came to GIH. I talked about applied sport science for ice hockey and the topics were concurrent traning, cross traning and hybrid training. Afterwards P-O told me that he had held a lecture in Toronto about exercise physiology at the Third International Conference on the Coaching Aspects of Ice Hockey in 1976, when the Canada Cup was played. Later he gave me cufflinks in gold with red maple leaves on which he had been given as a specially invited guest. As a fan of ice hockey I keep these along with my medals from different world championships and the Olympics 2006 when Sweden had both gold and silver for men and women respectively. I appreciate the cufflinks as valuable as the medals! Later, in the summer of 2011, P-O gave me a signed ice hockey stick from the players in “the big red machine” – CCCP – from the 1970s. I could just say wooow!

During his long and rich life P-O traveled around the whole world and contributed tremendously to the progress of sport and health science. As late as the week before Christmas 2014, he visited GIH and attended the closing dinner with students who took their exams.

Many many thanks and rest in peace P-O Åstrand! You have always been an inspiration!


Marten studied Sports Science at the Swedish School of Sports and Health Science in Stockholm (GIH) with focus on ice hockey. He has worked as an ice hockey coach for over 15 years with teams on the highest level and also participated at eight world championships and two olympics (juniors/seniors/male/female) as strength & conditioning and video (tactical) coach.

Marten is now a lecturer at the Swedish School Of Sport & Health Science (GIH) and a laboratory instructor at the laboratory of applied sport science at GIH, as well as a co-founder of Exxentric.

App under development

An Expansive Year for Flywheel Training

2014 saw inceasing numbers of professionals using flywheel training around the world and growing scientific support for flywheel methods.

For Exxentric, it has been a successful and eventful year, with more new customers around the world than ever and a successful launch of the kBox 3. Here is a recap of our year and an outlook at 2015, by our co-founder M.D. Fredrik Correa.

Exxentric Summit 20142014 was an intense year. Among our best experiences was starting a new tradition with the Exxentric Summit in Stockholm in May with participants from all over Europe. Our distinguished guests made it a very fruitful couple of days. We made many new friends and got new ideas for coming products and improvements. Afterwards we got a lot of positive feedback and, yes, we aim to make this a recurring event.

We also moved into the US market with a new local distributor as well as a reseller. It feels great to now be able to serve all the US athletes, coaches and institutions interested in flywheel training. In a short time our skilled partners have spread the concept of flywheel training widely in the US and connected with lots of great people in our field. The step to enter the US has also made a big impact as several articles about flywheel training on the kBox have been written by some of the very best strength and conditioning coaches, Chris Korfist and Carl Valle. We were even asked to write an article presenting our story and our concept of training in one of the most influential blogs for track and field coaching.

kBox 3As you might have noticed, at the beginning of December we launched the highly anticipated kBox 3 and started shipping it, initially to partners and key users. We are thrilled that so many of you have appreciated the improvements that we have been working hard with during this year. We believe that the new kBox 3 has set the standard for closed chain, multi-exercise flywheel devices with its increased versatility and ease of use.

During the first weeks after launch, your demand for the kBox 3 even outstripped our production pace. From January 2015 we will be going at full capacity at our new production facility in southern Sweden in order to minimise your wait for delivery.

On the scientific side we have seen growing buzz about flywheel training and eccentric training during 2014. We were overwhelmed by your interest in the article we shared showing the huge increase in start speed for swimmers who made flywheel lunges first (the Post-Activation Protocol). Articles and pods covering the topic of eccentric training are also coming at a steadily increasing pace, and we have started to share the best of them with you on social media (including our Facebook and Twitter profiles). Also, we’ve been really proud about all of you kBox users who are sharing images and stories about your flywheel training. We try to share and pass on as much as possible. If you tag your posts with our name we’re sure to find it (or use hashtags such as #kBox3, #flywheeltraining or #exxentric). Our prediction is that you will read a lot more about flywheel training in 2015, as researchers, coaches, athletes and personal trainers realise its potential when you want to get effective eccentric training in a safe way.

App under developmentAs we look forward to 2015, we have many things to get excited about. For example, in the not too distant future we will present you with an app-based and wireless feed-back system for the kBox! I can’t tell you much more about it but it is being tested right now in real training situations and will be launched in 2015. To the right you can see a preview of an early version of the app. The solution will be backwards compatible, so all earlier kBoxes with a SmartCoach sensor will be compatible with this new app solution. SmartCoach continues to be the tool for the professional coaches among you, while the app is developed to enchance the experience for those of you training on the kBox yourselves.

Also, as some of you already have seen, we’ve started to rework our web site, and there’s more to come. On the product side you have given us lots of ideas for development, and our ambition is serious. I can’t go into specifics but we can tell you that our R&D department has got a heavily increased budget for 2015 thanks to your increased interest in the kBox. This increase is aiming at presenting new products as well as accessories during 2015, so stay tuned!

Wishing you all a Happy New Year!

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

Flywheel Training Gaining International Momentum

What Every Coach Ought to Know About Flywheel TrainingFollowing the huge interest in flywheel training from Chris Korfist’s article on the subject in the leading blog Freelap USA, the editors became so intrigued with the concept that they asked us to write our own article about it. We were honoured, as Freelap USA is one of the world’s most influential training blogs for track and field, and top coaches around the world read every article that gets published there.

Our co-founder, M.D. Fredrik Correa accepted the invitation and our story was published this Wednesday. The article was quickly shared widely in professional coaching circles on social media. You can find it here: What Every Coach Ought to Know About Flywheel Training.

Now shipping the kBox 3

Today, we have proudly started shipping the kBox 3, the newest version of our versatile flywheel training device. Here, founder Fredrik Correa explains how the new kBox 3 will improve the experience for our users, based on his background as a professional coach.

Exxentric kBox 3With the kBox 3 we wanted to improve the user experience by making it even smoother to shift between exercises and users. It was already one of the most, if not the most, versatile multi-exercise devices on the market but that was something we wanted to improve even more.

A new automatic strap adjustment mechanism means that the tower is gone and replaced by a small lever the you can press with your foot. When pressed you can either pull out the strap or let it go and it will then be retracted. When the length is adjusted you just let the lever go and you can start working out. You still have the superior strap length compared to other devices and only need the extension strap for overhead exercises.

With the new strap adjustment feature you can shift from leg to upper body exercises in a second creating completely new routines with super-sets, circuit training and other High Intensity Training routines.

In addition, this change reduces the height of the kBox when packed for travel by 26%, resulting in a beneficial improvement of flexibility for coaches and athletes who take advantage of the unique portability of the flywheel training device.

A second big improvement is that the surface area is increased by 12.5%, without being larger in the base. In addition to the removal of the former strap adjustment tower, this change results in even more versatility and flexibility in the training. You can move around, go deeper in the squat or sit on the kBox without interfering with the tower. This will be very welcome not only to our taller users but to anyone that want to use the multi-exercise functionality with the kBox.

The third important change involves the re-designed foot supports to facilitate single legs squats and to give heel support for two-leg squats and patella and achilles tendinosis. These are so new that we haven’t even had time to make proper photos of them to show you yet.

We hope to set a new standard with the kBox 3 when it comes to flywheel multi-exercise devices. Going forward, we believe that coaches and users won’t accept a limited depth or range of motion in the exercises or that you have to bend down to pick up a rope or turn a knob to adjust length.

Today, we start shipping the first kBox 3 directly from our new and larger production facility, to meet the increasing demand in both quality and quantity.

Fredrik CorreaOur research and development section is never at rest, and we are eager to hear your thoughts on the design and functionality. Your feedback is what brought us here and we hope that you will help us to continue to improve. So if you have any thoughts, please contact us, or share them with us on Facebook or Twitter. Thanks in advance!

Eager clients have already pre-ordered the first week of production. If you are interested to get your hands (or feet) on the kBox 3, contact us or your local reseller today to request a demonstration or a trial. We are looking forward to hearing from you.

Happy DOMS,

Fredrik Correa, M.D.

The Case for Sophisticated Power Measurement

In a fresh article on the Freelap USA blog, olympic coach Carl Valle makes a great argument for the need to monitor performance during training and also to do this in a valid and accurate way.

When it comes to our kBox some people ask how to measure their work, which is a valid question. The answer is the SmartCoach system, which Carl also lists as a top 10 feedback system. The problem is that people I meet often want to relate the results “to my barbell squat in kg”. This is a different thing. My usual response is: “How can you compare if you don’t measure your barbell lift?”

Knowing the load on the barbells doesn’t tell your power output. It depends on the speed and the distance the load travels, and you have to measure this as well to compare. I hope more coaches and athletes pick up this from Carl and start to look at their training in a more sophisticated way, using all the benfits that new technology offers.

I’m also glad to read Carls fine remarks about the kBox, which in his words delivers “an unholy amount of force to the lower body” and that the kBox is the future closed-chain replacement of the Nordic Hamstring Curl. We think so too.

/Fredrik Correa, M.D.

Force comparison between barbell and kBox flywheel squat using force plates and SmartCoach.

Force comparison between barbell and kBox flywheel squat using force plates and SmartCoach.

New Study:
kBox Usage Can Make Swimmers Start 35% Faster

Swimmers that do lunge exercises on a flywheel squat device such as the Exxentric kBox prior to a race get a 35% faster start. This is evident from a new study from the University of Granada, which validates the so-called post-activation potentiation (PAP) protocol.

Georgy doing lunge exercises on the Exxentric kBox.Numerous studies have shown that using a flywheel device results in higher muscular activation and muscular forces during training. As a result, increases in strength and hypertrophy are higher during a flywheel training regimen as compared to using traditional weights.

Can this higher activation be useful in a race context too? The answer is Yes! Post-Activation Potentation (PAP) is a technique to elicit higher muscular force in explosive actions. This has been explained well in an excellent article by sports scientist Bret Contreras:

“The underlying principle surrounding PAP is that heavy loading prior to explosive activity induces a high degree of central nervous system stimulation which results in greater motor unit recruitment lasting anywhere from five to thirty minutes.”

PAP has showed mixed results in studies and the conclusion has been that the protocol (type of exercise, intensity and rest) before performance must be validated. It is therefore interesting to read a new publication from researchers at the University of Granada, who studied two different protocols for PAP before swim start. They compared them first to each other and then to warm-up only. PAP consisted of either three reps of barbell lunges (85% of 1 RM) or four lunges on a first-generation multi-exercise flywheel device.

Results showed that mean horizontal velocity in the swim start increased by 35% with the flywheel lunges as compared to warm-up only and by 18% as compared to PAP with barbell lunges. This flying start gave the swimmers faster times to 5 and 15 meters after the flywheel PAP and this protocol can give the swimmers a significant advantage in shorter events.

/Fredrik Correa, M.D.

To learn more about how your team could use the Exxentric kBox to benefit from these results, please contact us today.

“The Best Piece Of Equipment That I Have Come Across”

This quote about the Exxentric kBox comes from US based track coach Chris Korfist, who has produced 59 all-state track athletes in the last 22 years. We read his statement in a new article on Just Fly Sports about his work as a sprint coach. We wanted to learn more, so Exxentric co-founder M.D. Fredrik Correa contacted Chris to ask some questions. He was happy to share his views on successful sprint coaching and the benefits of using a kBox.

The Exxentric kBox

Fredrik: In the interview on Just Fly Sports you said that the kBox is “the best piece of equipment that I have come across”. Can you elaborate on that?

Chris: Most equipment on the market is just dead weight. In some cases, it is even less when you add pulleys and other devices that lessens the pull on the muscle. The kBox is more like sport. In most athletic movements, an athlete is required to respond to the force imposed on their body. For example, when running, an athlete has to absorb the force driving the body into the ground by springing back into it. In most cases, that amount is more than two times the body weight. On a regular piece of exercise equipment an athlete won’t experience that force, but he will on a kBox. An athlete has to stop that wheel and reverse it. Put a couple of discs on and an athlete will feel that force.

How do you use the kBox in developing faster sprinters? What exercises do you do?

As I mentioned, we try to get high forces into the athlete and try to replicate that same motion as running or jumping. To do so, we do single leg squats, split squats and regular squats using a variety of belts so an athlete can pull from different body parts. Some people recruit differently based on where the pull is originating, so I designed some other belts to have athletes drive from the muscles that I want to develop. The harness is great but some athletes feel too much back so I have rigged a belt that I can pull from different areas to get the individual to work what I want. We also wave load the different discs with the different exercises. We also do a hip hike for the glute medius muscle which works great with distance runners as well. And we do a psoas muscle knee drive that really gets a great glute/psoas combo. Romanian Deadlifts are great too for hamstring work. We will do RDL and then do a fly or single leg work and do an acceleration.

What advantages does the kBox offer that you can’t get with your traditional tools?

As I mentioned, the eccentric aspect is key to athletic development and the kBox offers the best in eccentric training. The flywheel mechanism is a great way to train reversal strength. You can see someone’s power by watching the wheel change directions.

After using the kBox for some time now, what effect do you see in your athletes?

I use laser timer and jump pad to constantly measure my athletes and I saw bigger gains this summer than I have in the past. I had a larger group of athletes jumping over 32 inches off a mat. And these are high school athletes. We saw similar improvements in block 30’s and fly 10’s as well. I also use a muscle lab to measure output in single leg exercises and have seen an uncommon jump in power output as well.

Sprint speed is crucial in many team sports. What are your basic tips for coaches in other sports when it comes to speed training?

Don’t put too many spices in the cake. Focus on one aspect of an athlete’s development. Bigger, faster, stronger is a myth. And rest is a workout. Let the body fully recover before going at it again. Most people never see what happens as a result of a workout because they get slammed with another one.

What advantages do you see with being able to do the training in the field?

The biggest advantage is to be able to do an exercise on the kBox and then go sprint or start or accelerate or jump. Appropriate rest is needed in between the two. The kBox does cause quite a bit of fatigue.

Do your athletes feel any difference between squats with high or low inertia on the kBox compared to free weights and if so, what do they feel is different?

The kBox feels alive. It is trying to pull you into the ground. A barbell just feels like dead weight. 2-3 plates on the kBox is a great eccentric workout.

That wraps it up guys. Hope you enjoyed the reading! /Fredrik

About Chris KorfistChris Korfist Bio Pic

Chris has been coaching track for 22 years in Illinois, US. He has coached high school athletes at Hinsdale Central, Downers Grove North and York HS, producing 59 all-state track athletes, three individual state champions, two team state champions, three 2nd place team finishes, and two 3rd place finishes. He owns the Slow Guy Speed School which is a gym that focuses on running and athletic development from which other all-state athletes have trained. He used to run the and web sites with athlete coach Dan Fichter. He also had the opportunity to work occasionally with some Olympic sprinters and other professional athletes.

What’s up with Exxentric?

Not much, you might think if you are looking at our frequency updating our news section. It is however rather the opposite. Our sales are rapidly increasing with new new markets appearing all the time.

In may we hosted a flywheel conference, the Exxentric Summit, with distributors, trainers, coaches and researchers from 9 different countries. We got together, shared ideas, research, protocols and had a lot of fun and this was a huge boost for our intensive work in developing new tools for our customers. Here are some pics from the Summit.

Other recent activities have been workshop in rehabilitation with our reference clinic Hela Kroppen in Stockholm and some private workshops and testing session with our newest advance in feedback technology, SmartCoach Encoder and force plates with enables you to measure force in both legs to see force curves during training, measure overload or imbalance between left-right etc. A really nice tool for a lot of our practitioners.
petre plates
Further on we are working hard to deliver all orders before our short vacation. Vacation really means that our factory is closed for a short while. We will still be working with development, handling orders, workshops and so on during that time.
Check back again after the summer so you don’t miss our new stuff that is coming up!

Afraid of muscle soreness?

Muscle soreness is familiar to everybody (Well, maybe not everybody but if you haven’t experienced muscle soreness, how the hell did you get to this post?!). Walking funnily, feeling pain during eccentric contraction (like walking down stairs), and experiencing muscle weakness are all classic symtoms of DOMS, Delayed Onset of Muscle Soreness. Not to be confused with the muscle soreness you feel in the end of a training session when you curl that tiny weight and it feels like you lift a small car, your training partner is screaming in your ear and you just want to go home and cramp up in a fetal position. That’s Acute Muscle Soreness, AMS, which is something else.

Back to DOMS. This all to clear message from our body that we aren’t as fit as we thought, is it any good at all?

Yes, DOMS is great. Read on!

DOMS develops during the next couple of days after a training session, always with the same pattern:

Day 1, “Hey that wasn’t so bad, I thought I would have this sick soreness, I think I’m pretty fit after all”.

Day 2 “Damn, those old glutes and hamstrings hurts as hell. Why can’t Earth be completely flat? All these stairs and slopes are killing me.”.

Day 3 “Mama!”.

DOMS peaks in about 48-72 hours after the training session. During DOMS you can experience muscle damage with a corresponding decreased in muscle function, an acute-phase inflammatory response (CRP for example; C-reactive protein), increased activity of myofibrillar proteins like Creatine Kinase, Lactate Dehydrogenase and Myoglobin. So, what is it that trigger this really unpleasant physiological response in my hard earn muscles? Mainly the eccentric contraction.

Eccentric contraction is when you resist a weight or a force that is elongating your muscle, for example lowering the dumbbell in a curl or lowering the bar in the bench press. One majestic eccentric exercise is the Nordic Hamstring Exercise (NHE). Most people will get DOMS just by watching others do this exercise, check it out here.

In short, eccentric contractions give your muscle a higher degree of muscle damage and subsequently, more DOMS, than concentric actions.

But there is one thing that causes even more DOMS than regular eccentric contractions.

-Say what!?

Yes, eccentric overload. Yes, I know, it sounds like a lot of fun, doesn’t it? Eccentric overload is when the force in the eccentric phase is more than 1 RM concentric. Eccentric overload has been shown to cause even further damage to your muscle, further increase inflammatory response and decrease muscle function even more during DOMS.

Great. But how is that accomplished then? Well traditionally with supra maximal weights and partners helping you in the concentric phase or pushing you down in the eccentric phase (forced negatives), using weight hooks or other inconvenient or impossible, dysfunctional ways. For a list of all stupid ways to get eccentric overload, check here. The smart way however is to use a flywheel device, like the Kinetic Box. By using auxiliary muscles in in the concentric phase and breaking harder in the eccentric phase or by overloading one limb in the eccentric phase after having used both limbs in the concentric phase, you get a high eccentric overload as easy as that! Without weights to break your back, and without partners. With high speed reps you will do eccentric overload as easy as it should be done, unassisted. And you will get the results you deserve.

But hey, what about the huge DOMS I’m getting. Won’t that be destroying my training regimen and break me down completely? C’mon, you are really looking to find an excuses to avoid this, aren’t you? But you see, the thing is that the eccentric training is protective against future training induced DOMS. This is called the repeated bout effect. By doing eccentric training you will not only increase more in strength and muscle mass more, but also protect your muscles from getting DOMS in the future. In training studies with eccentric overload the inflammatory and structural damages is attenuated during a training program with eccentric overload. One session of eccentric training has been show to have a preventive effective for up to 2 weeks!

The good news for you weaklings is that you don’t even have to get DOMS to get a protective effect. By doing low volumes of eccentric contractions with our without eccentric overload, while increasing the load step-by-step you can get the same effect in the long run, without being a cripple 6 out of 7 days a week for a month. Great! The same is seen with older people. Even senior citizens get a good effect from eccentric training. It is actually so that old people even better effect, since they get a higher degree of structural damage from the eccentric training.

Step-by step increase could look like this for the NHE for example (from Iga et al 2012; adapted from Mjolsnes et al 2004):

wk 1: 1 session 2×5

wk 2: 2 sessions 2×6

wk 3: 3 sessions 3×6

wk 4: 3 sessions 3×8.

Increasing load from 10 to 72 reps per week over 4 weeks. And this protocol gave a 21% increase in hamstring muscle torque i 4 weeks!

Well, if you step-by-step increase in training volume doesn’t work on reducing DOMS, studies have shown that coffee reduces pain during DOMS with 48%. Same numbers as for Naproxen.

So, get a kBox and grab a coffee and lets go! don’t fear the muscle soreness!

More posts on effects of eccentric training and flywheel training coming soon!

/Fredrik Correa

Some references:

Fire brigade goes flywheel

We are proud to present that the Greater Stockholm Fire Brigade has chosen flywheel training with the kBox to enhance their training. The kBox is a versatile tool for the firemen since the firemen goes through different phases with regular strength training, performance training and rehabilitation depending on injuries, tasks and performance. We are happy to serve those that serve us! Good luck with the training! To read-up on our former project with Brannkyrka Fire Deparment, check here.


Picture showing the firemen at Katarina Fire Dep. doing some kBox training during the introduction seminar. For more info how the kBox can facilitate and improve your training, contact Exxentric, Sweden.