Founder of CORE and GreenTEG– Wulf Glatz

First question that comes to mind is, I've seen a lot of wearables measuring skin temperature. What's the difference between core body temperature and skin temperature?

Well, the skin temperature is just the temperature on your skin, and that is heavily influenced or mostly influenced by the environment or the context. So, imagine you have a temperature sensor on your skin, and now you put on a jacket. What will happen is that, well, skin temperature rises, but your core temperature most likely won't change. Same if now, in winter on the Northern Hemisphere, you go outside, skin temperature drops, your core temperature remains stable.

People in the field have tried to solve that just with algorithms, and it's a more difficult task than people would think. So, what people are, if you're interested in health, then you're interested in a physiological parameter, a signal from the body. And if you just look at skin temperature, it's mostly a signal that gives you context. What is this person doing? Is he going to put out on a blanket, or is he going outside, or was the window opened? I mean, that can be interesting data, but it's not what most people are looking for.

And how does core body temperature change? Does it change every minute, for example, does it change every 10 minutes, and does this happen through activity? How does it work there?

Yeah, here, I mean, what is, why do we have a core temperature? Our body, the most important parts are where the organs are, and they have a preferred temperature. That's why we have something called thermoregulation. The body tries to keep all the important parts of the body at that temperature because that's the temperature where they like to operate, and they function best. Usually, that is around 37 degrees, and the core temperature is pretty stable as long as there's no heavy distortion.

There is some natural swing to it. Usually, what we see is that at night, the body temperature drops around half to one degree, whereas during the day, you have like a little increase, so you can go to 37.5 during the day and drop to 36.5, sometimes 36 during the night. That is really when the body recovers, it drops the temperature, and this is kind of a sinusoidal swing, a 24-hour rhythm, and it's correlated to your circadian rhythms, your inner clock.

That is one interesting aspect of it. Now, if it comes to sport, we see changes, and those changes can occur rapidly. And why do they happen?

So, if we work out, we use our muscles, and we produce force, and unfortunately, this is not super efficient. You can compare it to a combustion engine. So, also, our body is roughly 20% efficient. That means for every watt that we output physically, we produce roughly four watts thermal. So, you know, some numbers from cyclists, if they do 300 watts, they have 1.2 kilowatts of thermal output. And now, humans are pretty good at dissipating heat through various mechanisms.

The first mechanism is the body transports blood to the skin, to the surface, also to the extremities, the arms, legs, the face, and there is a heat exchange with the environment, and the blood is cooled down. And with the blood, you cool your body. Now, if you produce a lot of heat, and if, on top, it's a hot environment or you wear a lot of clothing, then this is not sufficient anymore, and another mechanism kicks in, which is sweating.

So here, we have evaporation, which gives you a cooling effect, which again, you still need the blood to transport this colder blood into the body again. But even with sweating and all the heat exchange, sometimes we come to that limit, and especially if it's hot outside, and we cannot dissipate all the heat that we're internally generating. And this is when the heat starts accumulating within the body, and the core temperature starts rising.

And the body doesn't like that, so it keeps working against it. It starts pumping more blood. That's when you know, usually, get a red face when I run. And now, this means a conflict because the same system is used to fuel our muscles. So, we need to bring oxygen to all the muscles, and now, if we need to cool a lot, then we need some part of the heart capacity, the pumping capacity, and parts of the blood to achieve the cooling, and that is missing for bringing the oxygen to the thighs if we're cycling, for example. And usually, we see a performance drop then.

What's really useful for athletes, I believe, is the lower you keep your temperature while exercising is better. But am I right, or how does this work?

Yes, I mean, we know that we need warm muscles to have good performance, but if they get too hot, then this can be detrimental to the performance. First, what I just explained, we can see if the body wants blood and heart pumping capacity for cooling, this is not there anymore for delivering oxygen, so we have a problem with the oxygen supply. Then, on a deeper level within the muscle, there's also then some biochemical reactions that can be detrimental.

And if the muscle gets too hot, basically, it becomes less efficient. So, yeah, it's not good to be at too high temperature, and we need to keep that in check and in balance.

Mostly, athletes are trained to ignore some signals and pain, so they go hard and keep going hard, and even if they have to go slower a bit, they keep going on, and it could theoretically get critical. That is really the sad part; it usually rather happens to amateur athletes that they overdo it and overheat, and they're running into heat exhaustion, which basically, the body switches into some kind of emergency shutdown, and you cannot move anymore, and you simply break down just to shut off the heat-generating part. That's like the ultimate thing your body can do to stop it.

That's a very interesting topic. I will bring up the conversation in a bit, but I wanted to also hear, what's the journey with CORE? How did you actually think about the idea in the early days?

So, it dates back to 2019. The background is, there is a company behind CORE, GreenTEG, and they do thermal sensors. We had realized that our main sensor technology, which is a heat flux sensor, is the key to solve this problem of measuring core body temperature. We had looked at what applications would be accessible for such a solution, and we had thought of sports, talked to the likes of Polar, but they said nobody's interested in the sports domain in this parameter.

So, we thought, okay, there's obviously some need in the medical space, so we kept developing the solution and had customer projects, but we had put the sport site aside. Back in October 2019, I was more of a private incident. As a father and entrepreneur, I'm usually quite busy, and I hardly ever watch TV. So, my wife was off with the kids, and I allowed myself some TV time after a long day of work.

And I'm passionate about sports, so I switched to the sports channel, and there was the Ironman World Championship in Kona going on.

It's a lengthy competition, so then they were showing in between they were switching to a scene that happened earlier the year. And that was in 2019, July, I think, the Ironman in Frankfurt, and there was an incident with an athlete, US athlete Sarah True. She was in the lead by 7 and a half minutes, I believe, after nine hours of competition, 700 meters to the finish line of the full Ironman, and then she crumbled and experienced basically a heat stroke and couldn't finish.

And I thought, well, damn, we would have a solution for this. If she had known or been advised like 10K prior, she could have run into the next aid station or basically walked the last five kilometers and still claimed her Kona spot or qualified for Kona that year. And then I did a bit of research and found out that the same thing happened to her earlier the same year. So I thought, okay, it obviously has relevance in sports, and people were talking about it.

The commentary was talking about it on TV that core temperature was critical. So I thought, okay, there's definitely a use case in the sports domain. So I went back the next day to the office and said, hey, we're not going to wait for the big guns. We're going to do our wearable ourselves. And there wasn't much time, but to set a high goal, I said like our goal is to be on the Olympic Marathon champion in Tokyo 2020.

And people thought I was crazy, but a few interns seemed to like the idea, so we picked it up. I had someone in mind who I thought would be a great product person to drive this project. I called him up, yeah, one day later, and basically got him excited, and then we started the project. And within, let's say, record time, we created the hardware, we had the manufacturing.

I actually reached out to the coach of Sarah True, and it's Dan Lorang, he's in Luxembourg, coach, and he's also the coach of that year's Ironman champions, both male and female, like Jan Frodeno and Anne Haug. So I thought, oh, he's like the number one in the game. And yeah, I was hesitating to reach out, but then I was afraid to miss that opportunity. So I just, you know, reached out on LinkedIn.

He was super friendly, was willing to meet. I met him in January 2020, and he was excited, and we agreed that we would test it with him and his team because he's also a coach in a world tour cycling team, Bora-Hansgrohe.

So we agreed to be joining the training camp, and that was planned for March. So we had a clear target; by March, we need to have like functional prototypes working to measure on these athletes. And so we got everything going, we had the prototypes, we went there, and like two days into the training camp, COVID hit. That was in Spain; everything was shut down. Chris had to go back by bus; you know, there were no planes flying anymore, and pretty much every sports event was canceled for the year, including the Olympics. So there goes my business plan; we're creating a sports product, and all big sports events are called off. 

Nevertheless, luckily, they decided that even though the Tokyo Olympics were pushed out by a year, which gave us more time, but they decided to have the Tour de France in, pushed out from July to September. And [Dan] liked the technology and how it worked, and so he thought, oh, we give it a shot and try it during the Tour de France. So that was our next goal. We went there, they used it. We couldn't openly talk about it, but it just word of mouth in the peloton, everybody saw it, talked about it, and yeah, I think right one week after the tour, the Giro d'Italia also delayed, started, and that was then we already had like three more teams, and then two weeks into the Giro, the Vuelta started, and there was another two or three or five teams. So we had like half of the peloton within half a year using or trying our technology. 

And yeah, from that, other athletes jumped on it. Dan also introduced us to Olaf Alexander Buu, who's the coach of the Norwegian triathletes. Back then, not everybody knew them, but they were really data-driven and tech-driven, and so Olaf really immediately grasped the concept and jumped on it. And we started a very deep collaboration, finally yielding to Christian Blummenfelt winning the Olympics and later on also much more world championships, and Gustav Iden, his colleague, winning Kona.

In the meantime, as a precaution, the Tokyo Olympics had decided to move the marathon away from Tokyo to the northern island of Hokkaido, 800 kilometers north, just to avoid the heat. So we couldn't fulfill that claim anymore for winning the marathon, even though I heard like some of the marathon runners apparently used it; we don't have track of everything. But yeah, we had an Olympic champion a year later.

And besides the triathlon, we had much more, for example, Richard Carapaz, who won the road race, men's road race. He usually was an Ineos rider, and they have a dark jersey, so you never see the core if they wear it now because it's underneath a jersey. Now in the Olympics, he raced for Ecuador, am I right? Yes. And they have a white jersey, so it was great; he won the Olympics, and you could perfectly see him wearing the core.

Then we had a surprise winner, the Austrian, for the female, Anna Kiesenhofer, and she had like  she's a mathematician, so she's not even a professional, and she had talked on Twitter about using and testing our sensor. So it made a bit of a wave in the cycling world. And so yeah, here we are, and it's pretty good penetration with professional sports, and now our task is to bring it also to amateurs and in other sports.

You mentioned word of mouth, and I'm wondering, what do you think is the most valuable thing that the athletes could find? Would it be because they could train specifically at a certain temperature, or is it because they would know when they needed to reduce their speed, for example? How would they use the sensor? And then also, I wanted to ask you about how do you really sell to such big athletes, but maybe let's keep it for a second question.

This is a very good question, and we're still on that, right? How do we deliver and show value to the user? Now, with professional athletes, it's somewhat easier because they have a coach to let's say digest some more technical stuff and just tell them what to do and how to interpret. And so that was our early entry into the sports, just collaborating with the coaches. So, how does it help? First of all, and the reason why people wanted to use it to prepare for Tokyo is everybody was expecting the hot, humid climate there.

And hot and humid is a worse combination because the humidity basically brings down the dew point and impairs sweating as a mechanism.

That's why hot, humid environment is so much more strenuous than a hot, dry environment. So, usually, it was not nothing new that people would do something like a heat adaptation or acclimatization, but there were just rough protocols where you basically say, okay, you just go there two weeks in advance, and you do your normal training, and initially, it will feel harder, and then, you know, you'll be acclimatized after a while.

And studies show this can take something between five and 12 days. And now, the athletes were only allowed to arrive five days before their competition in Tokyo, so a full, normal acclimation wasn't possible protocol. And so, what the core allows is to really optimally drive this process and even do it in different environments because all that matters is that your body is at an elevated temperature, and yeah, is exercising, and this is a trigger than the adaptation of the body.

If you exercise with an elevated temperature, your body will start adapting by optimizing its cooling, and it optimizes its cooling by, for example, earlier sweat onset but also by how to perfectly distribute and steer basically all your valves to bring the blood to the right positions in the right amount to get the most effective cooling. And what you usually see is that over time, by doing training at elevated temperatures over time, for the same load in the same environment, you will not heat up as fast, and that means directly you can basically output more power.

So, and now, the good thing is when you train to a temperature, you can always adapt. So, after a few days of training, you will have to push harder to get to the same temperature level and then get the same effect of training. If you would just gauge that with the environment and like a power load, you will, after a while, not get the same, let's say, load or trigger to your body. It will be just lower, and the effect will diminish, or you overdo it, and you have then detrimental effect if you overpace and you overheat.

So, that's why it's a useful tool for this acclimation. But another thing that people had studied and also observed just on an empirical level is during COVID, a lot of athletes were forced to train indoor, especially in cycling. So, a lot of people did, and some people used the fan just intuitively to cool down, and some didn't. And those who didn't, by accident, practice some heat training. And the performances we saw in the 2020 Tour de France were absolutely astonishing, very high level, like of the levels of back, let's say Lance Armstrong level. And retrospectively, it could be explained that they basically practiced some kind of a heat training.

Also, and what the studies then showed, if you do a heat training over the period of an acclimatization and continue to do that, you will even see some physiological adaptation. So, what the body does is it will build more blood plasma, so you, the liquid in your blood, so you have more liquid to work with to cool and to transport oxygen and blood. And now, it also detects then a lower concentration of red blood cells of hemoglobin, and it will eventually start the process of building more hemoglobin, and you end up with an effect similar to an altitude training.

So, you will, the body will start more red blood cells, and you can conserve this. If you have a steady heat training protocol, you don't have to keep it. You don't have to do such extensively, but you can now combine heat training with altitude training, but you always have to hit the right dose. And the core helps with that. So, that is, let's say, the performance-gaining part of heat training and ideally done with a core sensor.

Yeah, and another advantage that people quickly realized is strategic cooling or external cooling. So, something we can probably take a little bit of credit for, if you're watching ray footage, both in Ironman or triathlon as well as in cycling from four years ago versus now. Now, almost every athlete takes every opportunity to go to the aid station and not only pour water, drink water, but pour water over himself, you know, put ice everywhere.

I'm assuming that in the meantime, at the Tour de France, like 80% of the water they distribute to the riders is not drunk but rather spilled over themselves. And we could really see that in the signals that it's super critical to take layers of clothing off early enough before a climb, yeah, even sprinkle yourself on top of the mountain or halfway down to get the maximum cooling effect.

So, you go with a lower temperature into the next climb. So, that is another advantage. And finally, yes, there's the pacing part, but nobody wants to, let's say, slow down. But what you learn over time, when you observe your core temperature, it's much better and easier to maintain a lower temperature than to bring it down. Like the bringing down, it's like, forget about that, you basically have to stop.

But you can keep it in check. So maybe not follow every crazy attack. As for the triathlon, you know, try to use the downhill passages as much as possible for cooling down and so on and so forth. So, don't go like super overheated into the run. You will basically heat bonk. So basically, the athletes have to be much more tactical to keep their temperature down because otherwise, it's irreversible.

Yeah, it's almost impossible to bring the temperature really down if you still want to compete. I mean, you can still, what you see then is walking, yeah, that will bring your temperature down, and some external ice. But there's a couple of stories also then in indoor races, you could really see that, you know, people use fans, then they don't only use one fan but three fans or five fans and like see towels and so on and so forth, stuff you can't do in a normal race.

But yeah, it's thinking of it afterwards, it's so obvious, right? I mean, we're kind of like a combustion engine, and if you had, yeah, if you pair a Ferrari motor with a Fiat cooler, you know, you won't have much fun on a German autobahn.

From a product perspective, where do you go from here? Do you think that frequency improvement is going to help, or is it different form factor being or more wearables? How are you thinking about it?

I think, I mean, we've created now the awareness for the importance of this parameter, and our mission is to really get this to the people and to the athletes, starting with endurance. But we have the idea also in team sports, it can be relevant there. It's more, let's say, a tactical or safety aspect, like who to substitute, you know, you don't want to overdo, or there you can just substitute players.

You have problems in American football, for example, where usually they compete in autumn and winter, where it's not so hot, but the training is in summertime, and then they have a lot of gear as well. So unfortunately, there is almost fatal incidence at least on the college level almost every year, and these could be avoided with monitoring core temperature. More on the endurance base and going down to more the broader base of athletes.

Since we own all the technology, we have all the way to cooperate. We similar as for, let's say, the heart rate straps, you know, now every watch has heart rate, but still, like some people will wear a heart rate strap, those who are who put more importance on accuracy and so on. And that market will persist, and that's what we want to serve directly with CORE. But then by collaborations, we're not going to create an own smartwatch, but we're looking forward to partner, find the right partners to bring it to a broader base of audience.

And I'm convinced like within the next two to three years, we'll have it in watches. Actually, on the more consumer side, we have the first example, which is the WIING watch that had integrated the technology. Again, it's not as accurate, but for a more, let's say, amateur user, it's still insightful and yeah, an important parameter.

For an entrepreneur, what's the process of making such a partnership, like with WIINGs or with, you mentioned speaking with Polar before? What's the process of you creating a partnership with them?

Well, traditionally, we're coming from a B2B business where we are the sensor manufacturers, and we usually don't serve the end customer. This is really the exception with CORE. So it's a normal B2B sales process where you pitch a solution or partial solution, you believe there is a consumer or end-user need or there's a specific problem, and you pitch your solution, and then you get eventually get integrated.

It's a more lengthy process; you don't have everything under control. That can be strategic decisions, but that's a normal business. Now, for the CORE and the sports domain, I think we are recognized in the market on the very top end, and we see that there is a demand, there is demand from our users to be integrated into broader ecosystems. And so this really helps us to open doors with the relevant players and get in contact and let's say evaluate different ways of collaboration, which go beyond a simple, let's say, buying a chip or a license for an algorithm kind of integration.

And when it comes to the software side and the LLM today, I wanted to take your opinion. Do you think that the current LLM models are going to change the type of software that you are going to be creating? Is this going to be useful for you, or do you expect other companies to be working on them?

That's an interesting question. Probably, I'm not the right expert, or I have too little experience yet, or have seen what's in the market. I've seen that some, let's say, wearable companies are jumping on it, and it just makes sense from a common sense perspective, right? I mean, this is exactly the point where we are at now, where we saw, okay, we're going and selling through coaches, and for their athletes, the value becomes very apparent, and for the coaches as well.

But for the normal, let's say, amateur athletes, we need to provide more. We need to provide, you know, what does the athlete need, how does he need to train, and how can he, like, give the feedback, how he improved his performance? And there I see the opportunities with LLMs to be a more intuitive or faster, yeah, way to the goal. It's a question of insights. I think that, yes, indeed, when you have a coach, the coach is going to help you to inform you.

But then when you go to the amateur, then basically, the amateur would need to make their research and educate themselves about that. And I'm guessing that LLMs are going to play quite an important role because it's much easier to create the insight there.

Now, having said that, you mentioned at the very beginning that during sleep, the temperature actually falls. And I wanted to ask you more specifically about this. Why does it happen? Is it more beneficial to sleep with lower temperatures? And do you have some information there?

What, from the few, I'm not an expert, but from the conversations I had with some sleep experts, I learned that it is an absolute necessity for the body to cool down in order to have like a restful sleep. And this explains also why we have, why we struggle in very like, if you're more moderate climate and you're not used to heat, and you come to a hot climate, and you don't have any air condition, you really struggle to fall asleep.

And there, so the temperature is the main parameter for people that have struggle falling asleep. So, usually, just make your room colder, and you, it'll be much easier to fall asleep. And yeah, I've just witnessed that when with my little kids. So, I brought them to bed, and just before, you know, I'm basically holding them, and then all of a sudden, I feel like a heat rush; they're getting really hot.

But what actually happens is they're trying to get rid of heat. So, they bring all that blood to the surface, and you feel them getting hot, but they actually just, yeah, release heat. And then usually, like half a minute later, they sleep. If you feel that if you hold the kid, and you feel they're getting really hot, then you just have to carry on for one more minute, and they're done. So, it's somehow, yeah, it's just a state where it's easier for the body to, you know, slow down with everything, all the metabolism slows down, and maybe also the regenerative processes are working better at that temperature. But it's, I don't know the biochemical reasons, but that's what the expert told me.

Awesome. Let's speak a bit about the team in GreenTEG today, in CORE. Well, what's your philosophy in general about the team, and how many people are you, and how are you thinking about team building?

Well, now in CORE, we're roughly 10 people, and in GreenTEG, we're roughly 40 to 50. So, what is in, well, how do I go about team? So, I usually, you know, like people that have the drive themselves, that have some entrepreneurial mindset, that are ambitious to take on responsibility and drive a project themselves. So, that's the ideal case. You don't find that always. Then, everybody has its limitations, and then it's really helpful if people accept and see those limitations themselves because there's no problem with it.

You can distribute work, you can delegate stuff, but you know, you should know where your boundaries are. That is really helpful, and I think we have a good mix in the team of very diverse, very international, and you have to find the right person for the right job. And yeah, and sometimes, you need to readjust. That can be, yeah, because the environment has changed, or the task has changed. So, there are different periods in a company where you need a different skill set, and sometimes people can easily adapt to it, and sometimes not.

So then, we have to readjust. In general, yeah, I like to have a culture where people feel responsible for their task and, yeah, and I have to sense a certain drive.

Excellent. For my last question, I'll make it a double question. First of all, if we, let's say, we speak in five years, where is CORE going to be? And then the second one is, what's your expectation about the future of sensors and wearables? What's going to be happening in the future here?

So, in five years, hopefully, core body temperature is not going to be the only parameter or insight we are delivering. We're currently working on a couple of other parameters; it's a bit too early to disclose. But which can be quite important, both in sports but also in the general health aspect, and they're all related to basically the thermoregulatory part of the body, which I believe is a really important and critical function of health.

And so, I see as CORE as a brand will have, you know, a product probably more in the, let's say, high accuracy, premium segment, and most likely, the core temperature will be a commodity that is available in various wearables and is just as normal to track as, you know, as heart rate is today. So, um, that would be nice. Would be nice if it was still associated, so with some co-branding to CORE. Then, the general wearable space, I see a bright future because we haven't talked too much about the more medical aspect of it.

But if we want to, let's say, break out of the ever-increasing health cost dilemma, we need to really have a paradigm shift, that we try to keep people healthy instead of just always only react when we're already sick. And the only way we can achieve that is, or one of the bets we have is, okay, we have to monitor healthy people already in order to see any early deviations and give them feedback on how to live and eat in order to stay healthy. And I think that wearables will play a key role in that. And yeah, hopefully, we'll have a small part in that.