51: The Ultimate Time-Saving Workout | CAROL Bike and REHIT with Ulrich Dempfle

Ulrich Dempfle: So, so rehab was developed by scientists, so it's a, a really scientifically studied program to develop the shortest, most effective. And most accessible way to, to exercise. 

Michael Kummer: And I was, I was on the bike for the first time, and then there was another dude, he was, you know, pretty fit, the crossfitter, I remember he told me.

Michael Kummer: And I remember him getting off the bike and just sitting there for half an hour, trying not to throw up. 

Ulrich Dempfle: But the, um, very sad thing is that less than 5 percent of Americans, meet government guidelines for aerobic exercise. 

Michael Kummer: I'd rather spend 40 seconds doing something than 45 minutes, 

Ulrich Dempfle: right? You get the same result.

Ulrich Dempfle: You don't get fit during a workout. You always get fit in the recovery periods between 

Michael Kummer: workouts. What happens during those 2x20 seconds in terms of what you feel on the bike? You're listening to the Primal Shift Podcast. I'm your host Michael Kummer and my goal is to help you achieve optimal health by bridging the gap between ancestral living and the demands of modern society.

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Michael Kummer: Hey, Ulrich, thanks so much for joining me today. Today, we're going to talk about ReHit. Which is the same as HIIT, it's different, and I want to find out, how different is it? What's the benefit of reduced exertion, high interval, high intensity interval training?

Michael Kummer: Um, how is it better? Um, you know, and how does a mechanical engineer get into reHIIT and fitness? So maybe let's start there. 

Ulrich Dempfle: Sure. Sure. Sure. Um, well, thank you so much for having me. Um, maybe first, first, how did I get into this, uh, by accident? Yeah. Um, so I'm a mechanical engineer. I first started in German automotive industry, very cliche, uh, as I'm German, as you can hear from my accent and then worked, uh, actually in healthcare for the majority of my professional career, working with hospitals and healthcare.

Ulrich Dempfle: uh, systems to improve patient care and to improve patient care, the most powerful, important, um, thing you can do is prevention. And then the most powerful measure in terms of prevention is exercise. Um, but the, um, very sad thing is that less than 5 percent of Americans meet government guidelines for aerobic exercise.

Ulrich Dempfle: Um, and that, that's really. Tragic, given what we know about the benefits of exercise that so few people, um, can do it. And so we, we firsthand in working with healthcare systems, so we, we, um, manage designed, ran chronic disease management programs for people with chronic conditions like heart disease, diabetes, and so on.

Ulrich Dempfle: and still couldn't get them to exercise, even if their prescription, literally their prescription is exercise. It's still very difficult to get people to exercise. And when you survey why they don't exercise, the number one answer is lack of time. 

Michael Kummer: Yes. 

Ulrich Dempfle: There's a debate whether that's just an excuse or an actual reason, but if you think about how many distractions we have today with endless, uh, whatever reels and Tik Toks and Netflix and so on, so the competition for time is intense and there's like billion and trillion dollar companies, um, who are really good at competing for people's time.

Ulrich Dempfle: So, so we, um, we actually believe people when they say they have no time. And so our approach is, well, how can we get all the benefits of exercise in the minimum amount of time? And that's, that's basically how we got into that because we, um, We stumbled across, stumbled across, re hit, so that's reduced exertion, high intensity interval training, um, in 2012.

Ulrich Dempfle: And for us it was like a light bulb moment where we thought like, my god, that could be something to really shift the needle. Um, and literally, yeah. We went, uh, like I went the very next day after I heard about ReHIT, it was on a BBC documentary, it was like showcased how effective it was, all the benefits of it with the, with the leading researchers, I went to it.

Ulrich Dempfle: an equipment shop and bought myself, um, a regular stationary exercise bike. And I actually paid close attention as to what features I should have so that I could perform the re hit sprints as they were demonstrated on that BBC program. Unfortunately, it was nothing like they had, um, showcased. So I couldn't do it.

Ulrich Dempfle: It was like really hard. It was not easy. I was sweating loads and it, it just felt very difficult to do. So, um, the enthusiasm dropped off quickly, but, uh, my co founders, uh, weren't willing to give up that quickly. And so we, we reached out to the scientists who were featured, featured on that program and the very first thing, like literally the very first thing after we've asked, like, why, why doesn't it work was like, well, you need a special bike.

Ulrich Dempfle: And they explained to us that in their labs, they had, um, is lab equipment, um, is very expensive and, uh, is operated by a lab technician that, that coaches the, the subject, the person who does the training through the workout. And we tried it and yeah, perfect. And if you do it as prescribed, as designed, it's actually a very good experience.

Ulrich Dempfle: Like, yes, it's intense for a very short amount of time, but it's a, it's a great experience. And they had, they had showcased it as an exercise that you could even do in your suit. Yeah. Like at work in your suit. And yeah, if you do it right, that's, um, that's possible for, or that would be possible for many people.

Ulrich Dempfle: Because you don't sweat. You don't get to the point where you start sweating, right? That's true for most people. Exactly. Exactly. There are some people who have like, who sweat loads and then, so we don't give a warranty for that. But, um, for the majority of people, it holds true. Um, but having, having a second person next to you to operate the bike for you and coach you through it, that's, that's obviously not practical for a mass market application.

Michael Kummer: Because you need to adjust the resistance, right? On the fly or on the fly kind of, you know? 

Ulrich Dempfle: Yes, exactly. Exactly. Exactly that. And so, um, that triggered us, that spurned us to, Uh, say, okay, well, we, we can do better than that. We can develop a fully automated, smart exercise bike that coaches you through the workout that, uh, makes all the adjustments.

Ulrich Dempfle: to, to give you the optimal workout every time and develop that as a solution. That's, that's actually simple, simple to do for like a normal consumer. And that, that's, yeah, that's like we started in 2012. Many prototypes and a lot of hard work, uh, went into it, but we, we think we have now a really good package to, to, to, to do re hit yeah, that's, that's our bike is fully optimized for that.

Ulrich Dempfle: And now we probably have to explain what re hit actually is. Um, um, so, so re hit is, is a improved form. of hit. Yeah. Most people, I think everybody here listening will be familiar with high intensity interval training and, and hit short workouts, very intense. But they don't take very long, right? That's right.

Ulrich Dempfle: But a typical HIIT program still lasts usually between, I don't know, 20 30 minutes. And the difficulty of it is, um, the rate of perceived exertion is very high. And so it is actually difficult for people to do. And certainly in a traditional HIIT workout, you sweat loads. And so scientists Perceived 

Michael Kummer: exertion, that's an important aspect, because it's not that re HIIT is easy.

Michael Kummer: And if not But it appears to be easier because of the very, very short time duration, like seconds versus 

Ulrich Dempfle: a minute, right? Exactly that. So, so ReHit was developed by scientists. So it's a really scientifically studied, um, program to develop the shortest, most effective and most accessible way to, to exercise.

Ulrich Dempfle: And so a ReHit session. consists of only two 20 second sprints. So you have a very light warm up, a first 20 second sprint, where you go all out, then a recovery, second 20 second sprint, where you go all out, and then a cool down. The whole workout can be done in as little as 5 minutes. The longest it takes is 8 minutes 40 seconds.

Ulrich Dempfle: Um, and so where HIIT offers high intensity training, ReHIT offers maximum intensity training, where you really push your body to new limits a very, very short period of time. And that creates a very powerful training stimulus that makes you much fitter and much stronger and gives you the same benefits as a 45 minute run.

Ulrich Dempfle: would give you, but in a, a much compressed, uh, 

Michael Kummer: timeframe. Right. And, and so, you know, for someone listening, say, Oh, you know, I have, you know, 40 seconds of, of work. How can that possibly do anything? What's, because it's, it's different than, I mean, I could go out and, you know, just run fast for, you know, 20 seconds, rest for two, three minutes and do it again.

Michael Kummer: And yet you're not going to get the same effect. So what's happening during a rehab session, both on a physiological level from a, on a molecular level, really, what happens with, what gets released in your body? What is the, the nervous system? How is the nervous system responding to the stimulus? And, and why does it work?

Michael Kummer: And, and why is it so much more difficult than just going, you Like on this, you know, special bike than just doing 20 seconds fast, as fast as you can on an assault bike, which is, you know, you know, one of the modalities that I do a lot as part of my CrossFit training. Yeah, sure. So 

Ulrich Dempfle: there's a lot of questions there.

Ulrich Dempfle: I'll try to answer them, um, one at a time. So one thing just, uh, I think people need to, um, be clear about is, um, you don't get fit during a workout. You always get fit. in the recovery periods between workouts. Um, and that's true for, for any exercise and it's true here. So the workout just has to provide a stimulus and then, um, you, you want to have that stimulus, uh, two to three times per week and you, you get fitter and stronger in the recovery periods between the workouts.

Ulrich Dempfle: That's the first thing. Then, um, the second thing about, Um, so what happens in those re hit sprints is that we are effectively simulating a fight or flight situation, an emergency situation, where you have to either, um, fight for your life or run for your life. And. Um, when you do a rehab sprint or rehab workout on KaroBike, in the sprints, we create a, a sudden spike in energy demand that's, uh, about a hundred fold greater compared to rest.

Ulrich Dempfle: So it's very rapid onset of a very, um, yeah, almost extreme spike in energy demand. And your muscles would usually. The preferred mode of operating would be to burn energy, fat, sugar from the bloodstream. With that sudden increase in energy demand, the muscles are unable to take the energy from the bloodstream.

Ulrich Dempfle: Instead, they have to tap into local energy stores. Um, so, Exactly. So the first 10 seconds is actually, um, it burns through, uh, what's called phosphocreatine. That's like immediate, uh, energy, but you have a very, very limited supply of that. And then the next thing is, uh, glycogen. So muscular glycogen is a storage form of sugar, um, and that's essentially your emergency energy reserve.

Ulrich Dempfle: And you have quite substantial, um, energy reserves stored in your muscle. And now what, what happens is, um. Because you're signaling to your body that, um, it's in a, in a fight or flight situation, the muscle actually mobilizes a lot of glycogen. Um, so it's been shown that you can mobilize with those sprints 25 to 30 percent of the glycogen stored in, in your, in your thighs.

Ulrich Dempfle: Um, and that's an awful lot of energy. Um, and in those two 20 second sprints, We, we actually use only very little of it. So, um, glycogen is a, is a large molecule of, of branch polysaccharides. And, um, but instead of mobilizing like, uh, just a few of those molecules. And, and burning through them as a whole, we mobilize lots of them and just nibble at the outer branches.

Ulrich Dempfle: And so the, the body mobilizes loads of glycogen and then uses actually quite little. Yeah. And, and that's also the reason why two 20 second sprints are basically enough and, and more would not necessarily give you more benefits. 

Michael Kummer: So what happens with the stuff that's not being used? 

Ulrich Dempfle: Um, that, that gets broken down after the, um, exercise.

Ulrich Dempfle: So you have for the 90 to 120, maybe 150 minutes after the, the, um, exercise and elevated, uh, metabolism, and you just, um, remove it and, and break it down in the, in the period after the workout. Um, but during the workout you use quite little and now the, the, the really important thing and. The best understanding of why this works.

Ulrich Dempfle: So we're very clear that it works. Yeah, and the best understanding of why it works is that There are certain molecules bound to the glycogen that get released as the glycogen gets Mobilized. So the first is AMPK that is bound to the glycogen and then further downstream, that, um, uh, releases and, and triggers the, uh, the release of PGC 1 alpha, which is the master regulator for mitochondrial cells.

Ulrich Dempfle: biogenesis. So therefore you're, you're, um, creating a very strong signal to your body that it has to get, um, that it has to build and grow a more and larger mitochondria. and therefore, um, increase your ability to, to burn through oxygen, you know, and that increases your, your VO2 max, and essentially you're getting fitter and stronger.

Ulrich Dempfle: There are other adaptations as well. So your heart gets stronger, it works both on, um, oxygen delivery and oxygen consumption, but the, the signal is basically triggered just by the, um, the, the, this rapid onset of energy demand, the glycogen mobilization. and the release of these signaling molecules with the glycogen.

Ulrich Dempfle: And what, what seems to be the case is that if you, if you have these maximum intensity sprints, that that's enough to saturate that signaling response mechanism. So it's a bit like, um, pressing, flipping a switch and, um, actually pressing the switch longer or harder, um, wouldn't really help more. And in fact, and here, so this is, uh, slightly crazy because you, it's, it's counterintuitive also maybe not fully understood, but.

Ulrich Dempfle: What seems to be the case is if you do more or longer sprints, that you don't actually get more benefits, but less benefits. So, and, and that's, that's really like, that's against everything else in exercise physiology that we know, because usually if you work out, it's quite clear if you do longer workouts or harder workouts, you get more benefits.

Ulrich Dempfle: That's just how it is. But what seems to be the case there is that. If you do more sprints, so three, four, five sprints. or longer sprints, 40 seconds, 50 seconds, one minute, you actually get less benefits. Um, and so the, the thought, the, the explanation that, that scientists have come up with, and this is, this is like a hypothesis.

Ulrich Dempfle: Yeah, nobody knows this for sure. Yeah. Is that, um, basically psychology kicks in. If you know that you have to do more and longer sprints, that 220 second sprints are just Uh, short enough for you to really push to your limits and go all out. If you know that you have to do six sprints and they're going to be 40 seconds each, you're not going all out anymore.

Ulrich Dempfle: You hold back, you, you basically pace yourself to, to, couldn't, 

Michael Kummer: right. I mean, there is physiologically, it's impossible to have six sprints and, and go all out. I mean, you, but your, your, your performance is going to, I mean, even between my two sprints, the second one. is significantly below the first one. And there is not, it's not in my head.

Michael Kummer: I just can't do it at, you know, any better. Yeah, 

Ulrich Dempfle: exactly. And so the beauty of two 20 second sprints, um, Is that it's, um, they're, they're almost over before the pain kicks in. So, um, I can get, um, and I, I don't, I, the last 10 seconds always suck , I, I, I would argue the last five seconds, so I, I get quite comfortably through the first 15 seconds of a sprint.

Ulrich Dempfle: And then the last five seconds get hard. Now I'm, I'm very adapted to this. So I've, I've done, I've counted the, I've looked amongst my various accounts and the, the production and the development environment done like 1500 of those sprints in my life. So, so that's, that's a lot. So I'm, I'm well adapted and accustomed to it.

Ulrich Dempfle: Um, Uh, clearly, this is intense, yeah, it's not a free lunch, it is intense, and it feels like a good workout, yeah, um, but it's, I would argue it's psychologically quite easy to, maybe not easy, but simple to do. Because it's so short and by the time the, the, the, the pain kicks in, you are, you're actually through it.

Ulrich Dempfle: So, and I do other types of workouts as well. So, so I, not every weekend, but many weekends, I also do a 5k run while the children have football training. Um, and I, I find a 5k run, if I have to run for 25 minutes, like every step is kind of like I have to push myself and it's hard. Yeah. Whereas, um, for two 20 seconds.

Ulrich Dempfle: Uh, I, I, that's much easier to actually push through than these extended, prolonged, um, periods. And we, we see it in our user data that we get good adherence rates. Um, and that it seems to be something that, um, that people can fit into their, into their, um, usual routine. Yeah. 

Michael Kummer: Yeah. No, I absolutely agree. And, and, you know, just in terms of intensity, I remember, I'm not sure if you do, but when we met that was a paleo effects, I think many, many, yeah, yeah, yeah, yes, yes, yes, I do.

Michael Kummer: And I was, I was on the bike for the first time. And then there was another dude, he was, you know, pretty fit the crossfitter. I remember he told me, and I remember him getting off the bike and just sitting there for half an hour, trying not to throw up. And. 

Ulrich Dempfle: So that's, that's right. And, but that's why we, um, one thing that we, um, so as, as when you first start using the bike, we usually have, um, what we call ramp up rides.

Ulrich Dempfle: So you start with just two 10 second sprints so that you actually know what it feels like, what happens, how your body reacts. Um, and then you do two 15 second sprints, then you do two 20 second sprints if you want, or you stay at the 15 seconds or the 10 seconds layer and which, which, um, also deliver a benefit are substantially easier until you work up your way to, that you can actually kind of tolerate it and, and perform it frequently.

Ulrich Dempfle: Because like really in, in terms of, for all exercise, um, adherence is, is the key. is almost like the only thing that matters. Yeah. Um, so, and, and so that's, that is really our primary focus. I know like effectiveness, efficiency is super important, but really what we care most about is adherence. And we feel that, um, kind of re hit, On a car or bike is actually something that, um, is, is strongly habit forming and that, that helps you build a routine and that helps our users to have something they can, um, a stick to, and also to have something you can fall back on if you're, if you're like going through a very busy period or so, to have, to have something that you, that you can always do, that you can always fit in.

Michael Kummer: Oh, I agree. Um, So if I have a red, I've had a saw, if I have an assault bike, right. And if I wanted to do those two times, you know, 20 seconds, there are a lot of people who say, well, you know, that's exactly what I can do. I don't need a special bike for that. Yeah. Maybe let's walk through the. What happens during those two times 20 seconds in terms of what you feel on the bike.

Michael Kummer: Yeah, sure I remember well every time I go on the bike, you know, the first couple of seconds, you know is literally, you know You pedal as fast as your muscles can twitch, right? There is no resistance or very little at least not nice, you know Yeah, like You know, it's just enough. So you don't, if you have tried already, like on a regular, you know, road bike, the going downhill on first gear, you know, you can't pedal.

Michael Kummer: It doesn't work because there is not enough resistance, but with Carol, there is just enough resistance to make you go as fast as you possibly can. Yeah. Right. Um, and then it increases, right? Slightly. 

Ulrich Dempfle: That's right. That's right. So, um, So the reason and like going back to the, the, uh, the beginning of our conversation, kind of, uh, why do you need a special bike?

Ulrich Dempfle: Um, so re hit works because you momentarily push to your limits and you really get to your maximum intensity. To get to maximum intensity and to reach your limit, you need to do, um, like basically three things. You need to apply the. Optimal resistance. You need to apply it at the optimal time at the right time.

Ulrich Dempfle: And that is just after you've built up, um, a lot of speeds and reach basically your maximum cadence. So you start pedaling at a very low resistance, very, very fast. And then your optimal resistance has to kick in rapidly in a fraction of a second, go basically instantly from very low to very high. Um, and, uh, then it's also really helpful to, um, basically get coached through that because if you, if you just tried it on a regular bike, like I did, Even though I had seen on the BBC documentary that how they did it in a lab, I couldn't replicate it.

Ulrich Dempfle: And, um, I was going way too hard in the recovery periods. Um, the sprints were not good and I didn't get to, to maximum. So, um, and that's what, what, uh, the bike does. So the bike doesn't have any, um, buttons. It's fully kind of computer controlled with automatic resistance. Um, you, you through the screen and the, the voice coaching, you're, you're coached through the workout.

Ulrich Dempfle: And so we try to make it, and I think we've got there really, to make it as simple as possible to perform this re hit workout and um, get make it as easy as possible. And um, what our bike also does is um, because we But we have a lot of data. We have, by far, the largest rehab database in the world. Um, I mean, orders of magnitude higher than our, um, academic partners, for example, because the, the, the studies they do, the, the, it's, it's limited in participants and, and how much duration.

Ulrich Dempfle: And we have, um, tens of thousands of users now over years. So we have way, way larger data set. So based on that, We can, um, when you start, um, calculate what we believe your optimal resistance to be, and then, uh, so, and that's based on, you know, your, your biometric data, your, your demographic data. Um, and then the, um, as you, as you do the workouts, we can fine tune it based on your performance and we will find your optimal resistance level very quickly and then keep adjusting it.

Ulrich Dempfle: Um, as you get fitter and stronger, or also reducing it if you, if you had to take a break off training or you had an injury or so, um, and, and that makes it, makes the workout suitable for, um, yeah, I'd like to say any age and fitness level. Um, so we, we have from my 15 year old sons to it and my 81 year old mother.

Ulrich Dempfle: does it. Um, and no, she's one of our very, yeah, yeah, yeah. She's, she's 81. She does it every other day. She texts me that her high scores. Um, and, and that's, it's quite remarkable because she, she does have mobility issues and finds, um, for example, walking, um, more challenging, 

Michael Kummer: but 

Ulrich Dempfle: on the bike, she can still do like a really effective workout to keep her cardio, um, as good as possible.

Ulrich Dempfle: Yeah. Um, and, uh, so it's a, it's a very personalized, um, workout that's just, uh, easy to perform and there's, So when you do it on the air bike, so, um, the assault air bike for sure, it's an interesting alternative. And if you have access to an air bike, um, you, you can try to do re hit on an air bike because the, the workload on an air bike also increases quite rapidly as you pedal faster, um, and, and you can get to very substantial power output also on, on, on the air bike, the, the drawback with an air bike is.

Ulrich Dempfle: that it's essentially a bike with one gear, you know, so you have one defined relationship between, um, pedal speed, cadence and power output. Um, and so if you have, you know, a CrossFit athlete, uh, CrossFit athlete like you, Um, in your thirties or early forties, I don't know. Um, okay. Then, then the air bike might actually be a really good match.

Ulrich Dempfle: However, for my mother at 81, the air bike would for sure not be a perfect match because it would be much too hard for her. So the Carol bike has, um, 255 gears. And we personalize and optimize the resistance, um, continuously. And so, so we can tailor it much more to individual users, which, um, an air bike couldn't do.

Ulrich Dempfle: And then there's, um, other things that with an air bike, the resistance increases as you pedal faster. We can really let you accelerate first and then kick it in. Um, so I'm sure we, we, we. eek out a little bit more in terms of, of power and really getting your legs to work at maximum. Um, and, but, but yes, on the other hand, airbag is, is for sure lower cost, but then it's also a bit noisy.

Ulrich Dempfle: It doesn't give you all the data, the dashboards and so on, the tracking. Um, we, we tried to build something that's really optimal for rehab and I think we, we managed that quite well. 

Michael Kummer: Yeah, no, no, I, I totally agree. I mean, there is, you know, the other thing really is you cannot possibly outgrow that bike.

Michael Kummer: You know, I've, I've noticed from back in, I don't know what it was, 2018, 2019 or whatever, when you went first. Um, and you know, my scores back then, I think I just crossed a thousand Watts or so. That was like thousand 81 or so, I think I have, um, and now my best score that I've never reached again, by the way, but also probably because I haven't done it, uh, as, as, uh, as often as I did a while ago, uh, uh, 1700 and something.

Michael Kummer: I don't know how I did it. 

Ulrich Dempfle: That's outlandish. Yeah. That's, that's a very, very, uh, high score. So that's, um, the, the, not many of our users, um, achieve that. During a 10 second sprint. Okay. 

Michael Kummer: Wow. Yeah. Yeah. Yeah. Very impressive. I don't know. Everything must have come together, but usually, you know, But anyway, you know, even now when I go on it, you know, and I hit like the 14, 1500 or so, it's as challenging as it was the first time I did it, you know, it never gets so like, Oh, you know, now I, now, and I've got it, you know, no, you never got it.

Michael Kummer: You always get off that bike and you're like, holy moly, I'm done. And, you know, I, because you said before glycogen, you know, I, I wear a continuous glucose monitors, you know, on it, you can see a, you can see a clear spike like in cross during CrossFit workouts where your body dumps glycogen. I mean, there is.

Michael Kummer: You know, you, you can see it. Um, if you want to measure it yourself, if you don't believe the science it's there, you can obviously tell, you know, um, the other day what I did, it was, it was a big mistake. I jumped on the bike and then right after into a sauna because I had to do a sauna test. Okay. How different types of saunas impact my cardiovascular system.

Michael Kummer: And usually I stay in for, for half an hour, you know, the highest possible after a, at minute 15 in the sauna, because I got into the sauna, my heart rate was still 105, you know, my resting heart rate is somewhere between high 40s to low 50s. And that was 20 minutes after the bike, you know, so I got in and my heart rate was still elevated.

Michael Kummer: And at 15 minutes, I had to get out of the sauna because I was at 147. And I'm like, I'm done. I can't, I'm not recovering. I can't do it anymore. That's how much of a prolonged impact that bike had on my cardiovascular system. And I consider myself to be relatively fit. I'm sure you know, you, you get that afterburn effect that you alluded to before where you can continue burning calories even after getting off the bike.

Michael Kummer: So it's not just the eight minutes or 40 seconds, you know, of, of, of actual work. for significantly longer where you keep burning calories, your, your metabolism remains ramped up and you, you know, get benefits. Uh, yeah, 

Ulrich Dempfle: exactly that. Exactly that. So yeah, we've, we've done a study on that and we, we know that about two, two thirds of the total, um, calorie burn from those workouts happen in the 90 minutes after the workout.

Ulrich Dempfle: During the workout, you do burn calories. some calories, a modest amount, but then with the afterburn, it actually becomes meaningful. So when I do, um, uh, a workout, I do this pretty much also every other day. That's just habit. It's easiest for me. I don't have to think about it. Um, and, uh, so then I have a calorie burn in total of something like 210, 220 calories, and that's, that's meaningful for, for my, my body.

Ulrich Dempfle: Body size and weight, uh, in terms of just, uh, helping with keeping my metabolism up and, um, being active and, and, yeah, managing weight, all, all of those things. So it is, it's a meaningful calorie burn with that afterburn. 

Michael Kummer: Yeah, and, and, you know, to put it in context, that's based on 40 seconds of actual work.

Michael Kummer: I mean, this is because, and if, you know, if you go for a 45 minute walk or, or a jog or whatever and see how little calories you actually burn. and how well that matches up with what you burn during 40 seconds. You know, even if weight loss is your main thing, I mean, it's almost a no brainer. I'd rather spend 40 seconds doing something than 45 minutes, right?

Michael Kummer: Yeah. Get the 

Ulrich Dempfle: same result. Yeah. I mean, I mean, we would always, so the, the, in terms of benefits, the, the, the key benefits are really is one cardiovascular fitness, improving your VO two max, and with it longevity benefits and so on, the other is metabolic health and, um, avoiding, lowering your risk of getting something like type 2 diabetes and so on.

Ulrich Dempfle: Those are, those are our headline, the primary benefits. For weight management, I mean, for weight management, the number one, by some distance, is what you eat. Yeah, for sure. Diet, diet makes the most difference there. Um, certainly it adds to your, to your calorie consumption, uh, your calorie burn. And, um, the, the other thing where it's, um, very helpful and can make weight management easier is around insulin sensitivity.

Ulrich Dempfle: Yeah. So, um, what does happen is, um, as you release lots of glycogen, um, the body actually wants to replenish that, uh, quickly. Um, after, after what's because it's, it's, it is the emergency energy reserve and the, the body wants to be ready for whatever happens next. Right. So, um, first you have lots of capacity to, um, put store sugars also away again.

Ulrich Dempfle: So that's, that's great for managing your blood sugar levels. And the, the process is regulated by, by insulin. And so having, um, and therefore improves your insulin sensitivity. And if you're, if you're insulin resistant. Then, um, just weight management becomes quite harder because you can't, so even if you carry lots of energy stored in fat and your adipose tissue with you, if your insulin resistance, you just have a much harder time to access that.

Ulrich Dempfle: Um, and if you have, um, if you, if you have, um, a good insulin response, um, it's, it's just easier to, to access your, like the energy that you, that you have, that you carry around with you. 

Michael Kummer: And when insulin sensitivity, I think is one of the key factors in any metabolic disease. I mean, even, you know, cognitive issues like Alzheimer's and dementia, their own glucose issues in the brain basically, or lack of insulin sensitivity, meaning insulin resistance where cells don't, you know, don't accept the glucose anymore because they're either, you know, they don't respond to the signals of the hormone insulin.

Michael Kummer: And so improving insulin sensitivity, I think. You know, is one of the key things that I'm concerned about for my own, you know, health and, and longevity. Um, and that's also one of the reasons why I like Carol so much because I can see. My blood sugar response. And every time I get off, I know that I'm a little bit more sensitive to insulin because of what I just did because of 40 seconds of workout.

Michael Kummer: But Elena, um, now one thing you mentioned it before as well, you know, Carol is designed to put you into fight the flight mode. It causes a dramatic stress response. Right. Um, and I kind of compare it, even if though it's not the same to cold plunging, right. It's jumping to cold water. Right. and you get an immediately fight off.

Michael Kummer: I mean, you're in shock mode and your, your brain is like, you're going to die. We need to do something about it. 

Ulrich Dempfle: So I mean, it's totally right. And in fact, um, uh, some of the, the, the mechanism why you see benefits from co plunging are actually. Um, the, the similarities, um, as I understand, um, some of the benefits from, uh, cold plunging also comes from the release of, of PGC 1 alpha, which is this master regulator for mitochondrial biogenesis.

Ulrich Dempfle: Right. And, and so there's, um, well, kind of the, the initial stimulus is quite different. The kind of the, the, the downstream adaptation pathway is quite similar actually. Yeah. 

Michael Kummer: Right. Yeah. Nope. And, and the real, or the second reason why I'm bringing this up is because there, a lot of people see things, you know, black or white, meaning that there are, there are those who say, okay, you have to push yourself every day to the red line, otherwise you're not going to improve.

Michael Kummer: And then there are those who never want to push themselves. period, you know, and always go the convenient route. I've learned, even though I've, for most of my life, I lean towards the, you know, if you don't throw up, you're not doing it right. Kind of, you know, I was in that camp for a long time, but while I'm old enough that I've realized that in our modern lives, with all of the stressors we are exposed to, even the good stressors can make your glass, you know, spill if your stress levels are already maxed out.

Michael Kummer: So, and I think that might also be a reasonable truth if that was the case. If that was the case or, or, or not, but from the get go, you told me, you know, three times a week care is enough, you know, more doesn't necessarily lead to more benefits. And, and I've come to realize even with my, my workout routine, pushing it every single day, considering in the stressful environment that I live in.

Michael Kummer: is not conducive to optimal health because it's too much stress. You know, even if it's good, even I used to do sauna bathing, cold plunging, Carol, you know, every single day, then CrossFit. Sometimes I did Carol, then I went to CrossFit, you know, and you know, and I realized, okay, you know, that's too much stress, you know, and I think that, Even with Carol as well, you know, I think you're probably better off if you do it on a day where your stress levels are lower than if you're already maxed out and you come home after a day of work and you're like, you know, I can't deal with that anymore, but I have to do Carol now and stress myself even more, that might be counterproductive.

Michael Kummer: What's your take on that? 

Ulrich Dempfle: Yeah, sure. So, um, first, um, in terms of, I think it's good to, to be aware and know. What is actually like how much do you have to do and then keep that in mind and for depending on what your goals are For for cardio respiratory fitness. It seems that actually two times per week is might be sufficient for for metabolic health Three times per week is for sure better than two times per week But no, you don't have to do it every day because you need to give your body Yeah, time to recover and in that periods, then you can grow back and grow, um, fitter and stronger.

Ulrich Dempfle: Um, so certainly on the other hand, it's so short, like the reduced exertion. Um, that when, when I, when I've discussed this with the scientists and they are the leading scientists in the field, they've also said like, um, they, they probably don't see a massive downside if you were to, if you wanted to do it every day.

Ulrich Dempfle: You don't have to, and giving your body time to recover is for sure, um, a good strategy and a good choice. So, I, I do it three times a week, um, and that's what we recommend to our customers. Right. Um, if you, now, there, there are, of course, um, so, just to be clear, there, there's many other things you can do with the bike.

Ulrich Dempfle: It's, it's optimized for re hit. Right. But it's, it's also a very versatile bike that allows you to do, um, longer fat burning sessions or, uh, zone based training, zone two sessions and so on. So if you have a lot more time than for example, um, doing some longer, um, low intensity workouts like zone two training, um, that that's for sure a valuable addition.

Ulrich Dempfle: Um, but it's, you, you work then at a different intensity and it's, um, uh, it's obviously also much longer. So this is really. If you have the time, then, then that's a useful addition into, into the mix of, of what you do in terms of exercise. And then, and then there's obviously, um, the, there's strength training is super important.

Ulrich Dempfle: I, I spend probably a lot more time on strength training than I do on cardio, even though I have a company that, that does cardio equipment, but that's, that's, that's just how it goes. And, and kind of mobility work. So, uh, there's, there's a mix of things, but I mean, it has to be balanced, 

Michael Kummer: right? Have you ever tried, because I did this for a while and I've not found anyone, um, who has done this as well to, you know, kind of gauge if what I'm doing makes even sense, but I have this machine.

Michael Kummer: where I can control how much, how much oxygen I inhale. So I can switch between 10 percent oxygen and 90 percent kind of simulating, like, you know, being up on, on base camp at Mount Everest versus being then, you know, um, hyper oxygenated. And, and what I've done is I've, I've done the, the sprints. Um, well actually I, I did various protocols, but I tried doing the whole thing, uh, the whole nine minute, eight minute, 40 second protocol just on 10 percent oxygen.

Michael Kummer: Yeah. How did that feel? Awful. Uh huh. You're breathing like through a straw and, uh, but it has really, it has, it had a dramatic hematocrit. And oxygen carrying capacity, you know, obviously you don't want to do this. So then you don't want your blood to get too sick. Otherwise you might pass out or have other issues.

Michael Kummer: Um, but I wonder, has anyone ever tried this, especially in a clinical setting or in a, in a scientific setting to see if that positively or negatively Impacts the benefits you get from the bike. 

Ulrich Dempfle: Yeah, um, so I can't speak too much about it. I know that we have, um, um, that we have commercial customers. So gyms, uh, and, and quite advanced biohacking studios who routinely, um, combine the carob bike with the, uh, Um, I think they use the Live O2 or so, Live O2, I'm not even sure, um, for, um, some of the longer workouts for the, the fat burn workouts that, um, that they, uh, with, with elevated oxygen levels to like some of them.

Ulrich Dempfle: So. Um, the, the, in the LA area, um, smart fit method, I think a very good outfit. Um, they have a bunch of different, um, uh, locations there. They, they use it routinely with, um, I think elevated oxygen levels. Um, so yeah, that, that does exist, but it's, it's not something that we routinely, um, recommend or, um, sell.

Ulrich Dempfle: So this is, there, there you're at the, really at the bleeding edge of, of. biohacking, stupidness. Well, yeah, I mean, that's, and, and that's fair enough. If you, um, this is kind of the N equals one, uh, studies to see whether, whether it works for you, but that, that is really the bleeding edge. And I, uh, I've not come across a scientific citation that would, um, exactly match those two methods.

Ulrich Dempfle: Okay, cool. 

Michael Kummer: Well, I think that we, we went through, covered a lot of, a lot of grounds. Um, I really like how you explain certain things and, and how it's different and why it works. I really think it's a no brainer. I mean, we've had that, the bike, I mean, it's second generation now, but starting out with the first gen, uh, you know, again, 2019 or so, um, and it, it does work.

Michael Kummer: It's, it's brutal if you want to, I mean, maybe one more thing, you know, when you are doing those 20 seconds, if you don't go all in. You don't see the benefits, right? So it's not, you know, Oh, I'm going to just go half ass, you know, if you do that, it's not going to work, correct? 

Ulrich Dempfle: That's right. So we, we do want, so we clearly encourage people to push and go all out.

Ulrich Dempfle: Um, one thing I would say, if, if 20 seconds, um, are just too long, Um, it's okay to do 15 second sprints, or we have like an option where you do, um, three 15 second sprints instead of two 20 second sprints. And, um, that from like, this is direct user feedback. And also in terms of large data. Um, it seems that the, the, the stress that we induce is similar.

Ulrich Dempfle: There's the same peak heart rate, but the affective response. So how users feel afterwards seems to be better. Um, so, so one, one can, there's so, so three, 15 seconds is I think, uh, uh, pretty good. a valid alternative. And the last five seconds do kind of, if those are the ones that hurt you most, then why don't you cut those out and do three sprints?

Ulrich Dempfle: It's a little bit longer overall, but, um, that that's quite promising. Um, and yeah, otherwise, even two 15 second sprints, um, have benefits very clearly, and then use that to build up your fitness until you're, um, you're there. And it's, Yes, push to your limits, but the making it a little bit shorter can make it can make a huge difference to be honest.

Ulrich Dempfle: Yeah. 

Michael Kummer: All right. Sounds good. Well, thank you so much. I appreciate it. It was a great talk. Um, where can people find you and, and your bike? 

Ulrich Dempfle: Yeah, sure. So, um, Uh, on the socials, on all socials, we're at the carol bike. Um, our website and our web store is carolbike. com. Um, you can purchase a bike there. Um, now we, we don't, uh, operate showrooms.

Ulrich Dempfle: We are in, um, uh, some of the, the kind of more, yeah, biohacking studios and, and personal training facilities in the more advanced ones. But generally we don't have showrooms. Um, but what I would point out, if you, if you do get a bike, if you purchase a bike and first you get free delivery and we offer, we offer a hundred day risk free trial, that's really industry leading that's nobody else offers that.

Ulrich Dempfle: So you can, um, use the bike for up to a hundred days and that's easily enough time to see. whether you like it, whether you can stick to it and whether you see the benefits. So that's very clearly enough time to, to make up your mind. And if it's not for you, we also pick it back up and you get a refund.

Ulrich Dempfle: So, um, that's a, um, that's something we operate because we don't have showrooms. So yeah, carolbike. com. That's the place to go. All right. Sounds good. Thanks. Okay. Appreciate it. Good. Thank you so much.