Exercise 2.0: Building Tech to Electrify Your Workout and Stimulate Better Results



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Jun 13, 2023

Exercise 2.0: Building Tech to Electrify Your Workout and Stimulate Better Results

“We haven’t invented a new way to work out since the ancient Greeks. With electro muscular stimulation, we're breaking that.” Invention is a big part of everything Bjoern Woltermann did at Katalyst to bring electro muscular stimulation, or EMS, to the US market – and to US homes. EMS workouts have been around for decades, but typically only in a physical therapy context. With Katalyst, you wear a suit that triggers your muscles while you work out, promising the equivalent of a 2-hour workout in only 20 minutes, and with less injury risk than a traditional workout. But to make this suit work at home, Bjoern and his team needed to invent everything from special sensors to custom textiles.

On this episode, we'll hear how a long-time back problem led Bjoern to discover EMS training in Germany, and realize the untouched opportunity for bringing it to the US. And we’ll go deep to understand how Bjoern and his team created a fascinating mix of hardware, software, sensors, textiles, and content and then stitched it all together.

Listen to Bjoern Woltermann, on Crafted, Artium's podcast about great products and the people who make them.

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Full transcript below — but we recommend you listen for the best experience. 

Bjoern Woltermann: Generally technology had massive impacts on humanity if it made it easier, a bicycle, a car, a plane, a phone. So it made things easier, made it better. We haven't invented a new way to work out since the ancient Greeks. The ancient Greeks were lifting rocks. They were wrestling, they were running. The Olympic Games are still the same. So with electro muscular stimulation, we're breaking that. It's literally the plane where there were steamships before.

Dan Blumberg: That's Bjoern Woltermann, Founder and CEO of Katalyst, an exercise system that uses electro muscular stimulation, or EMS, to revolutionize your workout. With Katalyst, exercisers put on a suit that stimulates their muscles as they exercise and promises users the equivalent of a 2-hour workout in only 20 minutes and all in a way that reduces injury risk because you don't need to lift any weights. Katalyst is a fascinating mix of hardware, software, sensors, content, body mechanics, and even custom-made textiles that they had to invent. On this episode, we'll go deep to understand how Bjoern and team stitch it all together.Bjoern Woltermann: We literally said we had an invention a day. What are we inventing today? That was literally what it was about.Dan Blumberg: In Bjoern's native Germany, EMS training suits are widely available at gyms. Meanwhile, here in the US, Bjorn discovered that hardly anyone had heard of the technology.Bjoern Woltermann: And this was like this eureka moment from me where I'm like, sorry, I'm sitting in effing Beverly Hills and you don't have this? Like how on earth, right? This is like the stuff is invented here.Dan Blumberg: Bjoern saw a massive opportunity to bring the benefits of EMS to the US and even more so to bring EMS to the home. No going to the gym required. But could he and the team get the tech right?

Welcome to Crafted a show about great products and the people who make them. I'm your host, Dan Blumberg. I'm a product and engagement leader at Artium, where my colleagues and I help companies build incredible products, recruit high performing teams, and help you achieve the culture of craft you need to build great software long after we're gone.

If you've never heard of EMS workouts or the Katalyst suit, imagine a fitted black suit with straps around your arms and legs and a tight vest. There's a kind of superhero mission impossible vibe to it.

Speaker 3: That was incredible. It was only 20 minutes?

Speaker 4: I am sweating profusely.

Speaker 5: It's the same movement, same everything. It's just your muscles are exerting more force.

Speaker 3: I'm out of breath, so it is real.

Speaker 4: It's totally different than anything I've ever experienced.

Dan Blumberg: The workout tends to blow people's minds and Katalyst can hardly make suits fast enough. They've been sold out for two years and there's a wait list in the thousands. But long before Bjorn brought this home version to the US it was widely used in gym settings throughout Germany. In 2010, Bjorn was working for Deutsche Telecom in digital product incubation and traveling extensively despite a longstanding lower back problem.Bjoern Woltermann: I was spending a lot of time in Israel, the west coast, east coast, did this for a few years, ended up 150 days a year on a plane, and my lower back blew up again. Like no shit, you know, surprise, surprise. So I was 20 days a month on painkillers, couldn't get out of bed in the morning. I was 35 at the time, so shouldn't be in that shape. So my physician sent me to a personal training studio using something called full body electro muscle stimulation training, which at the time I hadn't heard about before. So he sent me to this personal training studio and there were two individuals with a personal trainer having black suits on, wires everywhere over them and standing in front of two devices, having nothing in their hands, moving their arms and sweating like crazy. And I was like, is this a heated room? Make no sense to me what I saw.

So basically it's kind of like stim. You've used it on knees or hips or elbows and so forth. And stim technology is basically so gentle and safe to the body that you could use it after you're injured. So it's actually very gentle, but also efficient methodology to train your muscles. And the idea behind this type of personal training was instead of waiting until you're injured, you use it on healthy muscles and you use it all over the body combined with basic calisthenic movements. And within a 20-minute session, you are basically able to work out your whole body at a level that even in the gym is hard to do. Because you actively engage the muscle, there's no muscle left behind, especially in hard to train areas, which is like the lower back, your abs, your core, glutes, all these things that when you're sitting are basically underdeveloped. So I did this workout once, tried it, two days later I was like sore, like hell, what did I do? I did it every Monday at 6:00 PM. I did it for six weeks and then I woke up one Sunday morning and I told my wife, I haven't taken a pill in a week and I'm pain free. And that was miraculous to me.

Dan Blumberg: The miracle of the suit is not only how it reaches difficult to train areas.Bjoern Woltermann: During these 20 minutes, every 4 seconds there's a stimulation happening. And while the stimulation is happening, you go through basic calisthenic movements. You do butterflies, you do squats, you do lunges, biceps curls and so on and so forth. And what's happening is, let's use the biceps curl as an example. When you do a biceps curl, you normally create a force against a dumbbell. And what's happening in EMS training is your triceps is also being triggered at the same time. So your biceps engages against your triceps. So both muscles are trained at the same time. You have a neutral load on your joint because there's no external load from the barbell and they basically work against each other. So your body is working against itself or with itself and engaging a lot of muscle groups at the same time. There's no impact, there's no joint loading, there's no injury risk.Dan Blumberg: The revelation of this suit was topped by another revelation for Bjorn later that year on a trip to California.Bjoern Woltermann: We were sitting with some friends and couples at a barbecue in Beverly Hills. My wife was also a customer at the time of this training studio, started talking about fitness and hey, I do this with a suit and so forth. And everybody looked at her and like what are you talking about? And this was like this eureka moment from me where I'm like, sorry, I'm sitting in effing Beverly Hills and you don't have this? Like how on earth? This stuff is invented here. So for context, at the time Germany had 500 personal training studios like this. There were chains with like hundreds of studios already existent. So I identified it, like first checked out if the technology checks out, like is the science solid or is it a fad? Most things are just fads in fitness. They come and go, but does it really check out? And basically because it's been around in physical therapy for 40, 50 years at the time, we used it since the '60s, it is there. I mean, did you watch Rocky 4? Like Ivan Drago, where he's fighting the Russian. So I mean in this movie they literally have the American, Stallone is training with logs and the Russians are using all this high-tech stuff.Ivan Drago: I cannot be defeated.Ivan Drago: Soon, whole world will know my name. Drago. Drago.

Bjoern Woltermann: And literally in the '60s and '70s there's something called Russian Stim. They just literally took a sign curve, put it into the body and see what happens. So it was a very crude way to do it, but it basically worked. And what you found was like Olympian sprinters from Russia were competitive and no one knew where they were coming from. So it actually worked and has been working for a long period of time, and now it had been much more refined. And then in 2015 I decided to make this my mission. I wrote it down and said, I'm going to put a dent into the CDC statistics of health and wellness of the American people and embarked on this journey.

Dan Blumberg: Before he became a product and technology leader, Bjorn trained as a behavioral economist. So he has deep interest in motivation and how innovation can change lives.

Bjoern Woltermann: If we think about what we had 20 years of innovation and health tech or fitness tech and what they did is was basically two categories. They either were trackers or we bolted a screen on a device that already existed. And I'm not saying this in any negative way. It's like what we did is we motivated people to do something that already existed. There have been bikes, home bikes collecting dust for 50 years. Now we created a great experience around it and put a DJ on it and a hot model in front of it and so on and so forth. And now people were motivated. So it's the motivation axis to do the thing that they didn't like in the first place. Same is true for rowers. Same is true for weights, same is true for aerobics. Same is true for running. No one is helping me with the ability to do it. So we are always just moving on the motivation axis. All this tech is moving on the motivation axis, and this is coming down to really understand how do I make something easier? Generally technology had massive impacts on humanity if it made it easier, a bicycle, a car, a plane, a phone.

Dan Blumberg: Dishwasher.Bjoern Woltermann: Dishwasher, yes. So it made things easier, made it better. We haven't invented a new way to work out since the ancient Greeks. The ancient Greeks were lifting rocks. They were wrestling, they were running long, short distances whatsoever. The Olympic Games are still the same. Yes, we added pickle ball, I get it, yes, but we're still doing the same things. So with electro muscle stimulation is we are, we're breaking that. It's literally the plane where there were steam ships before and that fundamentally made it easier. So in a short amount of time without an injury risk, I need much less ability to work out. We have people that are hip replacement candidates and are working out. They cannot lift anything. They cannot walk up the stairs, but they can do Katalyst. So the thing that really broke it for me, made it so clear was I'm moving on the ability axis. I'm not only moving on the motivation axis. This is fundamentally different.

Dan Blumberg: And so you identified this really interesting technology, this crazy unmet opportunity in Beverly Hills and elsewhere. So what did you do next?

Bjoern Woltermann: I took a device to LA and I asked 20 of my friends in LA like, hey, I want to show you something. So I rented a hotel suite and every hour and a half I had someone come by, got them through the experience and gave them a questionnaire afterwards. What did you like, what did you not like? Do you want one? And so on and so forth. Figure out if this is something that Americans would even be interested in. And guess what? Something that works that's short and easy to do and is absolutely effective, guess what? Yes, Americans want that. So that really worked. But the feedback was I want my own suit. I want to be able to do this at home. And this was in 2013 for context, it was a year before Peloton launched. But the whole notion was already I want my own stuff. So I knew what they wanted, I knew what was possible. I learned about the regulatory environment and said, yeah, we have something here. It's valid, it's solid. It's like the economics pan out. The gap for me was hardware. I've never done electronic hardware. So there was an opportunity to hire a few folks out of Microsoft. I started building a first generation in late '16, early '17.Dan Blumberg: In the US, the suit was considered a medical device and needed FDA approval. In 2017, Katalyst got that approval, but initially the FDA categorized the suit as a prescription device, meaning it had to be used under the supervision of a trainer. So Katalyst introduced the suit to the US by opening a few studios.Bjoern Woltermann: So same model as in Europe at the time. The long-term goal was always to get it into the hands of people, but short term, that was the step that was possible. So we did a first step. What we did is we had a fully quantified device at the time. So it was generating a ton of data. It was all about understanding what's literally happening to the body, what's the right setting, what's the right intensity? And then in late '18, I went on holidays, had some time to think because I was going full throttle for two years nonstop. And I was like, I think I know enough to build a home device. And what I did was I said, so what makes a successful studio experience, like a studio training experience for the customer? And I created a matrix that was the role of the device, the role of the trainer, the role of the customer, and the role of the room. So what duties and what tasks do each of these four players in the experience have?

And I wrote it all down and then I said, okay, now if I do this at home, there's no trainer. Okay, that one goes out. The room is unknown. So there's only the technology and the customer. So to build a as good or better customer experience, I cannot load more duties onto the customer. So everything that was the duty of the room or that was the duty of the trainer, has to be covered by the technology, by the product. Can I do this with tech? Do I know enough about this? Can I build this like whatsoever? I'm not really sure how to do this, but there's a leap of faith. Sometimes you have to like, we're going to figure it out down the road. Monday morning I pulled everybody into a conference room, I still remember that, and I said, "Guys, we're going to stop what we're doing and we're going to build a home device." Like pale faces. People were like, how? What? We can't do this. This doesn't work. And everybody vetoed me, including my wife, who's technically the co-founder at the very beginning and she said, "I don't think this works. We can't substitute the trainer and still have a good experience."

Dan Blumberg: The number one concern everyone had was how at-home users would be able to judge and adjust the intensity of the stimulation for themselves without majorly disrupting their workout experience.

Bjoern Woltermann: I cannot play the piano and dance at the same time. That doesn't work. So what was basically the preconception was for someone to dance, someone has to play the piano and that cannot be the same person. So if that's all you know, me telling you I can build a tape recorder and you don't need the piano at all is unfathomable. People just couldn't imagine that.

Dan Blumberg: Bjorn knew he could make the suit a single-handed operation, but there were loads of other issues to solve first, starting with how to adjust the stimulation intensity.Bjoern Woltermann: If I want to keep the temperature in the room, let's say 72 degrees, I first have to know a thermostat to then have a thermometer to then build a thermostat to then heat or cool the room. There was no thermometer in EMS training. We did not know what the muscle contraction was. We did not know how much the right intensity was. The way it has been done before is someone was feeling the room basically looking at the customer, is this enough, is this not enough, and then making a judgment call. You cannot put this into tech. So I said, but I think I understand enough about the physiology of the body that I can build a thermometer in the first place. And then step by step by step, I walked the engineers through that. But it was like that groundbreaking, really, really first principle thinking what needs to be true that I can build this? So really dumbing it down.Dan Blumberg: Next challenge, the exercises themselves.Bjoern Woltermann: Okay, we need content. Someone needs to tell me what to do, great. But then the content needs to be synchronized with the impulses so that the impulse is always coming at the right time. So basically instead of the impulses are coming from a clock, they're actually coming from the timestamp of the video. That was an innovation. What we ended up building then is I said, while we record the workouts with the trainers, the trainers are working out themselves. So why don't we record everything that they're doing, create a telemetry stream of that and then personalize it to the end consumer? So basically now what's happening is much more elegant than we ever thought was possible.Dan Blumberg: They also had to consider the interplay between the suit, the trainer, and the user.Bjoern Woltermann: When the customer is then basically using the device and the app, he hits play, the trainer on the video is telling them what to do, so that job is taken by technology. The telemetry is being replayed in a time swing with a timestamp of the video, so that never goes out of swing. I don't have to touch it because whenever the trainer is touching the screen on the screen, so basically like I see the trainer touch the device, my suit reacts, personalized to myself. So it's a very immersive experience that we at the end of the day created by making sure what roles have to be transferred from the trainer to the app versus not delegated to the consumer. So the consumer actually today has a better experience without a trainer in the same room.Dan Blumberg: And then there was connectivity being applied in a feedback loop with a range of variables for each user.Bjoern Woltermann: There's a relatively large impact of what's your skin conductivity on the feeling and on the impact that the impulse has on your muscle. So the total impedance of the body is like it goes through the suit, then it goes through the skin. Is there hair on the skin? Is there cream on the skin? Is it thick skin? Is it thin skin in different parts of the body? How much body fat is there? How much muscle mass is there? And then it goes all the way and comes out on the other side of the body where it has the same stack The other way around.

Pressure of the suit, compression, has a high impact on how conductive is this? Is the hair compressed? Is it not compressed? It's like the water compressed, not compressed? So one of these things we said, this is happening so fast, we put it into the electronics, not even into the electric portion. So that's happening a million times a second. Then the next set is, okay, so what's the next impulse like? Okay, that's communication between Bluetooth of the device and the iOS. The timing, that's also happening. It doesn't get out of sync 15 times a second. So if we sync this every 500 milliseconds, that's good enough. So this is something that we're syncing that often. Okay, what happens if I have a Bluetooth disconnect? Okay, how does it negatively impact the experience? How often do we actually have disconnects?

Dan Blumberg: And finally, the needs of the suit itself.Bjoern Woltermann: So the suit needs some moisture to create connectivity between the electrodes and the skin. When you prep the suit, we can tell you the suit is ready or not. Where's the threshold? Is it 500 ohms? Is it thousand ohms? Is it 2000 ohms? Is it 10,000 ohms? Where's the threshold? So some of that was actually us trying out the suit and then putting the threshold somewhere, figuring out how does that feel? How does that feel? Is that wet enough? Is that not good enough? There was a lot of trial and error, but then also it was like, where in the stack do you solve the problem? These experiential versus architecture decisions, those were really interesting.Dan Blumberg: Yeah, I mean I can see how your combination of your experience, the behavioral scientists, the Deutsche Telecom, I can see how it all, it's all come together here. It's really fascinating.Bjoern Woltermann: I think the thing that really made us successful, so if your mindset is I know how this works, I've done this before, you're going to fail almost certainly. So an openness and curiosity, and Elon talks a lot about that, is this first principle thinking. If you have that mission statement clear, you can be successful because then you know what you're actually solving for. And for us it was I need consistency in the experience.

Am I very clear what I'm solving for? And then am I open-minded to come up with like, is this the most elegant solution? Is this the most elegant solution? Because adding more tech to it is super easy. Removing buttons, that was hard. We went into material science. At the end of the day, we created our own textiles that combine conductivity with water retention with, there's a color change so that you can see it's wet enough. So there was a lot of stuff. I had to learn seamless knitting, which is basically 3D printing for textiles. And I became a textile expert because otherwise we couldn't actually build anything like this. So what I'm saying is we had so many absolutely fundamental challenges that we had to overcome. We have three values in the company. It's called care, understand and lead. So you care for details and you care for each other and for your customer. But the most important thing for me besides care is understand. It's like you really need to understand the problem and you need to understand each other. And here it was understand the challenge so that you really can solve the problem. And even if the whole world is telling you this is the problem, it doesn't mean they're right. So those were really the fun moments. This is one of the biggest learnings, yeah.

Dan Blumberg: Yeah, I mean hardware is hard. It also, as you just said, it sounds like a ton of fun.Bjoern Woltermann: Yeah, definitely. So we spent a lot of evenings, second shift, basically like six to nine just with the engineers when I had my normal CEO job done and we spent just, okay, 6:00, beer's open. What's the problem of the day? In 2019 when we built this first generation of the home device, we literally said we had an invention a day. What are we inventing today? That was literally what it was about. And yeah, fun journey, but be very clear about what you are really sailing and setting out to achieve is important.Dan Blumberg: To help Katalyst scale and grow, Bjorn reached out to Artium. At that point, the pandemic had hit, the product was working, but Bjorn had been outsourcing all the software development and decided it was time for Katalyst to be more in control of its own destiny.Bjoern Woltermann: I was basically saying, okay, we're still going to stay outsourced for a bit, but have to really upgrade the infrastructure. We have to upgrade the quality of the software and the quality of the app, but also help us build a team. So basically it was kind of getting ready so that an internal team can take it over. I think you helped us get two or three engineers out of the team that we now have, and now we are in house. Basically we own the whole stack. But it was this transition period where for a certain amount of time, there was some cleanup, upgrading infrastructure, make it better monitored, make it more reliable, basically put these things in place and enable an internal team to really, really take it to the next level, but also help us get some of the talent.

Dan Blumberg: I always find it interesting when companies go from outsourcing to you now say you have your own internal capabilities. What was it that made you say, no, we have to be able to do this ourselves?

Bjoern Woltermann: If it's one of your core competencies or your core differentiators, which is the software experience around it, like hardware is important, so we own our hardware stack. Software we didn't own, but it's also a key differentiator. So we have to own that. So I'm a big believer to have in house what is your differentiator and key competency like differentiates you from the market? When I outsourced it, I didn't have a engineering leadership to actually lead the team, and I didn't have the bandwidth to do that. So I think once your team is big enough that you can have a director of engineering or VPN or something like that, then you can bring it in house. You cannot bring in house to engineers and hope they're doing the right thing. Who's leading that team? Who's leading that effort? Who's making sure the rhythm of business is there? Who's ensuring the rituals are there?

The other challenge also is for us especially, we need a lot of different skills. So we have textiles and firmware and hardware and iOS, and there's this AWS component, there's a streaming component. So there's so many different components that we have to touch. Generally with two engineers, you can't do this, so you need a little bit broader team. We were at a point where we wanted to own it where, hey, there's a shoot of new content on Sunday, something broke. People get up and fix it. It's not happening with an outsourced company. So this is why we're really happy with owning this in house.

Dan Blumberg: How are you thinking about scaling now? And I mean Katalyst is, it's a very premium product. You said you want to have a major dent in the CDC statistics of obesity and et cetera. How are you thinking about scaling impact? First of all, maybe you could actually share some numbers or context of where you are today and how you think about growing from here.

Bjoern Woltermann: We've been sold out for two years. Basically we're catching up with supply. In terms of accessibility, I mean the device currently, if you Affirm it's just 66 bucks a month. If you tell me you can't afford that to significantly improve your health and fitness, then I don't know. So the challenge really that we have is just from what we call premium products is the perception we are willing to spend money on things if we think it works, right? We're spending money on wine and beer and entertainment and movie theaters. I think price is not really the problem. It is people understanding that it actually works. So we had two returns in the history of the company. One of them said I can't afford it anymore, and the other one said, I have so many other things that I do. I like to do those. Everybody else keeps it, loves it, uses it. That's the point. So to date, we don't have any triggers. We don't have any push notifications, we don't have any emails you didn't work out whatsoever. And people are using the product consistently because the thing itself works. So we haven't even started on the motivation side. I don't even have a team for that yet.

Dan Blumberg: People have that intrinsic reward already.Bjoern Woltermann: Yes, exactly. So people are saying, I miss how my body feels like after I work out, and they literally get addicted to the thing itself. I don't need to tell them to do it, and that is the reason for me to be convinced, to convince myself this is so fundamentally different that I can reach the goal of changing people's lives at scale.Dan Blumberg: Amazing. Well, congrats on everything and I can't wait to see what comes next.Bjoern Woltermann: Yeah. Wonderful. Thank you for having me.Dan Blumberg: Yeah, thank you.Bjoern Woltermann: Great conversation. Thank you for your curiosity.Dan Blumberg: That's Bjorn Woltermann, and this is Crafted from Artium. At Artium, we love helping innovators like Bjorn build game-changing tech. If you're creating something big and bold, let's talk. We can help you build great software, recruit high performing teams, and achieve the culture of craft You need to build great software long after we're gone. You can learn more about us at and start a conversation by emailing hello at If you liked today's episode, please subscribe and spread the word about our 20-minute highly invigorating experience.

Bjoern Woltermann: During these 20 minutes, every 4 seconds, there's a stimulation happening.