Frank Pernett | Freediving Science

The Freedive Café Podcast | Episode #152 | Transcript















Listen to this interview …


The Freedive Café Podcast | Episode #152 | Transcript


Frank Pernett is originally from Colombia. He has been freediving his whole life and been involved in the deep freediving and freediving competition scenes for many years. He is currently based in Sweden where is is working towards his PhD under the watchful eye of freediving scientist Erika Schagatay

Frank is a wealth of knowledge about freediving science and physiology and today we discuss some of the traditional topics of freediving science that interest us most as well as some new approaches to understanding the dive response and we talk in detail about what can cause lung squeeze and what protocols we might follow to prevent them.



Frank’s lung squeeze prevention guide can be found HERE!



Frank, welcome to the show, welcome to the Freedive Cafe. So today we’re going to be having a wide-ranging discussion on the topics relating to freediving science. It’s been a while since we’ve done an interview on this topic, so I’m quite excited to hear what some of the more up-to-date information in your mind is regarding freediving science.


Tell us first a little bit about yourself, where you’re from, and how you eventually came to be involved in the freediving world.




Well, that’s kind of the story of my life. I grew up, I’m from Colombia, and I grew up on an island that is in the Caribbean, it’s closer to Jamaica even than the mainland of Colombia. So I grew up by the sea, and I was diving since I was six years old.


And with my brother, we started to get deeper and deeper. Back in those days, I’m talking about the 80s, we didn’t have enough information, so we were reading a lot of magazines. And in the end, we knew about Enzo Mallorca, Pelizzari, and we started to go diving.


In the end, that’s how we got into freediving competitions. I was competing a long time ago in the first editions of Vertical Blue, indeed, and I got some national records also. So freediving was part of my life.


I’m also a physician, and I did a speciality on internal medicine. And then another speciality on pulmonary medicine, that was driven mainly by my freediving passion. So I think freediving has been dwelling around my life permanently.


And now I’m doing a PhD that is focused on freediving blackout, but it was the opportunity to dig a little bit more into the diving physiology. So that’s why I moved from Colombia to Sweden to work with Erika Schagatay. A lot of people know about her.




Yes. So you’re working through your PhD in some kind of collaboration with Erika. And everyone, of course, is familiar with Erika as one of the leading names in freediving science.


Unfortunately, I just missed her. She left a couple of days before I got back to Dahab. And I also didn’t, unfortunately, have the chance to take part in the research that was being conducted here by her son at the time.


That’s fascinating that you… I didn’t realise that you were involved in the sport for so long. What is the name of the island that you are from in Colombia?




In Spanish, it’s San Andres, but it’s like St. Andrews.








I don’t know if you know Walid Boudhiaf, but he made some freediving competitions there, maybe three years ago.




Yes. And also, I’m familiar with some people who actually teach out there now. There is Christian, who’s teaching there.


I’m aware that it’s a pretty nice spot for freediving. Just as a little bit of, you know, reminiscence and nostalgia, like when you compare the first Vertical Blue competitions with how they are now, what would you say the main sort of differences are over the years, how things changed?




In the beginning, it was more like an invitation. So I think William, at that time, he was calling freedivers that he knew, because he wanted to have a special environment and to be more like a friendly competition, focused on the performance. And it was the first time that I believe that it was a competition that takes so many days.


And so you can go to improve your performance day after day. And nowadays, one of the biggest competitions in the world with a lot of elite athletes. And yeah, maybe I miss that there was like a mixture of top performances, and people like me, that I was like an average freediver.


So that talk between the experts and people that is just getting in, it was amazing. And I miss that, you know, that kind of environment. Now it’s more into the numbers.


And I think it’s a little bit different now.




Yeah, I mean, all communities and sports and activities change, you know, the groups, the people, the development is always changing, sometimes for the better and sometimes not so much for the better, but that’s inevitable. So freediving is undoubtedly one of the most unique sports in the world. What in your mind makes it so unique?


What do you think are the most unique aspects of freediving from a kind of a sports science perspective?




Yeah, I think our sport is so different. Just to begin with, most of the sports are related in a way with a maximum oxygen consumption in the end. It’s like we want to increase the heart rate and we increase the contraction of the heart.


In our sport, it’s the opposite. We are looking for just like shutting down a lot of the systems to save oxygen. So that is remarkable.


It’s one of the sports that you are not… Some people say that we are adrenaline junkies, but I think we’re the opposite. We don’t want the adrenaline.


We just want to get rid of it. And for me, it’s like that when people ask me why you would like to go deep 60 metres down with coldness and why?


And I say, to me, it feels like a deep meditation, the state of the mind and how do you feel during the dive? It’s something that you don’t have or at least I don’t have with any other sport. It’s kind of finding a connection or feeling that you belong to the sea.


To me, it’s that the feeling that you are belonging to the place you are diving. So I think that’s why our sport is quite unique.




Can you give us a bit of an overview into your own personal research into freediving? Like what areas you are focusing on?




In the beginning, I suffered a lot of lung squeezes and I was out of the water for maybe five years and I couldn’t dive at all. So that’s why in the beginning, I was trying to find out the way to get back to freediving. And I found a strategy to not get rid of, but to be safe regarding the lung squeezes.


So I would say that was maybe eight years ago. And I was also, because of my work, I was treating freedivers that were injured. And it’s something that I don’t need to say right now, but I feel that the lung squeeze is a different entity.


A lot of people see it like a pulmonary oedema of immersion that is very similar to the pulmonary oedema of swimmers, of scuba divers. But there is some evidence that it’s not an acute problem. A lot of people have chronic issues, it’s affected chronically from the lung squeeze.


So that’s in the beginning, that was my first area of interest. And now my PhD is mainly focused on the risk for blackout. So yeah, my main area is just about oxygen conservation and the mechanisms under the blackout.


But I was very much involved in the lung squeeze issue.




Okay. Yeah. I’d like to come back to that topic then and go into a little bit more detail about your experiences with squeeze and this strategy that you developed.


That’s always a very interesting topic on this podcast that I try to go into as much as possible. Before we get specific, let’s be a little bit more broad here. As a scientist, I often, no, not me, but when talking to a scientist, what I’d like to know, because I have my own ideas on what common misconceptions about freediving physiology or science might be.


What are the most common misconceptions about freediving science or physiology that you encounter in the community?




Yeah. First is when we we’re talking about science, you need to have data that backs up your ideas or your claims. And we lack that.


We don’t have enough research. In the field of lung squeeze, we are far away from having a real understanding, for instance. So what I found in the community is that some beliefs or some feelings, people grant that as evidence or they say, oh, I did this and I felt this, so maybe this works.


But it’s just your personal opinion. And most of the communication is based on what worked for me, that could have a physiological reason behind it, but you cannot claim that as a fact if you haven’t done the research. So I think that we have a lot of things to do regarding freediving, because as you know, research is driven by funding and it’s very difficult to find money to do specific research on this topic, because we are in a small niche of athletes and there is not too much money like in football or skiing in Sweden, as an example.


So, yeah, I think that the first misconception is to present the experience as facts or like truths, which is not real.




Yeah, somehow I feel like most of the community kind of understand the sense that we are very speculative when we talk about these topics, because we don’t have that data. But at the same time, like you say, it’s almost impossible to imagine that you would ever have the funding or the resources to do the kind of studies that we would really want to do, because I mean, there are other things in the world, you know, environmental issues and poverty and health issues that are really, really important for people that also need funding. I think that maybe the main risk in our sport is that if there are some studies done, that they might be done with very limited resources, they might have very small number of participants.


And then any of the conclusions that emerge from that might be taken to be very factual when they might need much more exploration or follow-on studies. Are there any examples of things like that that you’ve encountered in freediving science?




Yeah, lung squeeze, for instance. The causes of it are very difficult to analyse and to pinpoint which is the key factor. And in the end, whatever we say about that is just as we grab information from several cases that have been published and the personal experience and the similarities that it has with another, with different kinds of pulmonary oedema.


But we don’t know for sure, even if we are on the right track, or if we were talking about the physiological consequences or why we have lung squeezes. It’s just a mind exercise. We need to measure things that are, as you say …. it is very difficult to measure the liquid in the lung.


We can take it out and analyse the proteins, but that requires an invasive procedure that is also done in a very high grade clinical setting. So yes, it’s impossible to do it in that way. But I think on the other hand, we need to be clever and we need to use the resources that we have, because as you say, there are many things in the world, but we can make use of what we have.


And I think one of the biggest issues on freediving research is that we need to work together. There are very few groups working on freediving physiology. And I have the feeling that it’s like everyone is doing their own part and we lack communication.


So as you said, if we have very small sample sizes, if we combine efforts, then we can have bigger sample sizes. So I think it’s not a dead end. And one example is Erika.


She has been researching freediving for more than 25 years. And she’s a good example that yes, it’s difficult to find the money, but you can look for it and you can continue working on research. And if I’m going back to my actual research, the blackout is very difficult to study because you cannot force a diver to black out in order to see what is happening.


So we need to find different ways to analyse the problem and to have conclusions. But you know, it’s about the causes of blackout. There is also a lot of ideas that could be right, but we don’t have enough data to say that that is for sure the reason behind it.




Okay, let’s get into some specifics then. You mentioned Erika there, and it’s been many years since I spoke to Erika. We had a really excellent discussion the first time that she was on the show.


I think it must be going back almost five years now, maybe even five years. But the main topic of discussion was the dive response. Perhaps you could give us, also for those listeners who are becoming new to the sport and haven’t listened to the past 150 episodes of the podcast, a little bit of a brief overview of the dive response that we talk so much about in freediving.


What is the latest research in the dive response and has any new interesting information emerged?




Yeah, well, to put it broadly, the dive response is mainly a reduction on the heart rate and vasoconstriction. That is, a narrowing of the blood vessels that goes to the limbs and all the organs in the body. So the magnitude of the dive response, we measure it most of the time by checking how deep was the heart rate reduction. And also, and that’s something that is becoming more clear with the new research, is it’s not only how low can you get your heart rate, but also how low can you keep it.


Because in that regard, we have seen a variety of dive responses. There are a lot of different patterns of dive response. And so far, the pattern that conserves more oxygen is in the diver that has a very early bradycardia, that is, reduction in the heart rate.


And the deeper, the better. And that they are able to keep it at the same level during the whole breath hold. Because in some freedivers, they have a strong reduction, but then close to the middle of the breath hold, the heart rate starts to go up again.


And sometimes, and it’s mainly related with the amount of oxygen that you have in the blood, they have a second reduction. It’s what we call a second bradycardia. So the heart rate goes a little bit lower, closer to the end.


And it looks like it’s related with the level of oxygen. So if you have very low levels of oxygen, your heart rate is going to be going down a little bit more than that. But if from the beginning, you were able to have a very low heart rate, probably you are saving more oxygen and you will not have that second reduction on heart rate.


So it’s still the diving response and mainly the diving bradycardia is, I think is the best way to check how is your ability. And I’m not sure if a lot of people are checking how is their diving response when they’re thinking about training, for instance, that, okay, you need to train your diving response if you don’t have it. Because I have seen even what I call the paradoxical diving response, where some people increase the heart rate when they are diving.


So, the opposite to what it should be. So that’s something that every freediver needs to check in a way, how is my diving response going on? And the other part of the diving response, the vasoconstriction, is very difficult to measure in the daily life.


So we measure it by checking how is the flow in the limbs. And we can use, there is a new technology that is called NIRS (near-infrared spectroscopy) that is able to measure the oxygenation in some tissues. So you can put it on your legs and check how is the reduction in oxygen.


So it’s a way to measure how strong is the vasoconstriction, but it’s very difficult to do it. But the good thing is that usually if you have a strong heart rate reduction, you will have a strong vasoconstriction. They are different systems, but they are extremely correlated.


So if you have a very low diving bradycardia, probably you have a very strong vasoconstriction. So far that is the diving response. And maybe Erika talked about the spleen contraction, nowadays we don’t consider it to be part of the diving response because the spleen contraction has been seen in other situations, like when you are doing exercise, when climbing, when they are exposed to hypoxia.


So it’s not related just with diving. But the diving bradycardia is a unique feature of this. I think it’s the only scenario when you are getting low levels of oxygen and your heart rate is going down instead of going up, which is what happens when you are climbing or going to altitude, the heart rate is going up with the low levels of oxygen.


And we do the opposite when we are diving.




Right, right, right. That’s fascinating and a lot to unpack there from just a couple of, it’s interesting that you really just mentioned vasoconstriction and bradycardia here, where traditionally in the free diving education, you know, information, texts, manuals, we have quite a list of things, including the spleen contraction, which is still, like I live in Dahab, you know Dahab also, you know, so surrounded by freediving instructors and everyone, almost everyone is still going to list the spleen contraction as a part of the dive response, which Erika told me it wasn’t years ago. And I’ve been trying to convince people of this over the years.


But and I think her explanation was something along the lines that the dive response, the bradycardia, the vasoconstriction will be seen on each dive, but that the spleen contraction or the spleen’s ability to contract and release extra red blood cells would sort of happen over more than one dive. So it’s a different kind of a system. Does that sound about right to you?




Yeah, but also, as I told you before, some people don’t have a diving response, they don’t have bradycardia. So it’s not universal. You don’t have it in everyone.


I will say that 99% will have it, but there is a 1% that don’t have the diving bradycardia. And with the spleen, it’s the same. Some people will have it and another will not.


But, and you know, Erika is my supervisor, so we talk about this a lot. And she now believes that it’s also a very important part of diving, of course. But we don’t consider it to be part of the diving response because we see that response in many other activities.


We have checked that on skiers, on climbers. And so exercise induces some spleen contraction. High altitude also induces more of a chronic, what we call tonic spleen contraction.


So it’s something that is a mechanism, especially when you require maybe more oxygen in your blood. But it’s not only related to diving.




So that’s fascinating.




So it’s important, but that’s why we believe it’s not part of the diving response.




So my question about vasoconstriction, and if I, as an instructor, when I explain vasoconstriction to people, I usually start with the concept of peripheral vasoconstriction and the idea of the blood vessels, the capillaries in the arms and legs constricting the blood and moving into the centre, towards the centre of the body. Usually the reason given is that it is to spare oxygen, to move oxygen to the essential internal organs, to the lungs, the brain. And then usually as instructors, we’ll continue on to talk about hemocompensation, blood shift in the lungs, more blood moving into the capillaries surrounding the alveoli.


Is this correct, this description?




Yes, it’s correct. As you say, the vasoconstriction is the reduction of the size of the arteries and capillaries that are going mainly to the limbs. And the vasoconstriction, what it actually does is reducing the size of your body.


So, because you are shutting down a lot of tissue, that’s why the oxygen consumption is reduced because, you are shutting down muscles, especially in the limbs. And when you constrict the arteries, the blood has to go somewhere else. So that’s why it’s pulled to the centre and especially the chest.


So, yes, what you’re saying is right. Now, I want to clarify that the diving bradycardia is related with parasympathetic activation, you know, part of the neural system. And vasoconstriction is mainly due to sympathetic activation.


So that’s why I’m saying that it’s two different systems that usually oppose each other, you know, that the sympathetic activation and the heart, it increases the heart rate and the parasympathetic activation in the heart reduces the heart rate. But when we are doing experiments, we are measuring both. And that’s why I’m saying that they are extremely correlated, that we found that when the participant in the study had a strong bradycardia, we also find out that he has a strong vasoconstriction.


So now we know that if we’re just measuring the heart rate, we can also infer how the vasoconstriction is also working. 








Most of the time.




Okay. And then the next part of the question for me would be then, what is the relationship between vasoconstriction and depth? Because I have, perhaps maybe I’ve been programmed to think this way, but I have the feeling that the vasoconstriction is more related to depth diving and you would see more of it in the diver who is focusing on depth than somebody who is doing static floating face down in the pool.


Is this wrong the way I’m thinking here? Or do you see, obviously you probably need a study to clarify this, but would you see the same vasoconstriction in someone who only does pool disciplines compared to someone who does depth? 




Right now we are finishing a huge data collection. We were able to do a test on more than 100 freedivers because the answer to your question is not easy. The first reason is that it’s very difficult to measure vasoconstriction during actual deep diving.




Yes, of course.




When we measure vasoconstriction, it’s in what we call simulated diving. That is static apnea with facial immersion. So it’s a good way to mimic what is happening during diving.


And of course we compare dry conditions versus facial immersion. And yes, when you are doing breath holds in dry conditions, the bradycardia is less, and also the vasoconstriction is less. And it’s stronger when you are doing it with facial immersion and with immersion by itself.


But when we compare divers that were, you know, mainly pool based, against depth based, we couldn’t see a huge difference yet with that. This is something that we are still analysing.  (Is this because the divers are already trained?). We just finished one week ago the final data collection.


So that’s something that we want to answer. To check if the training has an effect on the diving response. And I will say yes, at least on the heart rate. We found that people that are committed and training, you know, almost six, at least six times in a week and doing specific training, they have a very strong diving response compared to people that are just starting.


So yes, it can be trained. But the question about vasoconstriction with deep diving, we don’t have the answer yet.




Very fascinating. I look forward to hearing more about that in the future. You mentioned that the lower the heart rate can go, the more beneficial.


And you also mentioned that the more stable this bradycardia is, then the better it is for the diver. Do you think that reducing resting heart rate in general is a good component of a free divers training methodologies? Or could it be completely irrelevant?




Now, of course, having a low resting heart rate is has been proven to be good for health. It’s a good way to estimate how fit you are, but related with diving? No.


Yeah, indeed, I have found some divers in whom the resting heart rate is lower than the diving bradycardia. So it’s like the heart rate is 48.


And when they are holding the breath, the lowest is 52. So that’s why I call it the paradoxical diving response, when they have a higher heart rate when they are holding their breath. Yeah, but it’s a because the resting heart rate has many inputs, and there are many reasons.


And heart rate is very complex. We used to believe that it’s not so complex but it’s very complex. What is, you know, commanding the heart rate? Even the lung volume affects the heart rate




It’s probably a good foundational thing to have in your training to work on lowering your heart rate anyway, just that it will improve most aspects of your health and therefore your sport too. Probably, but you may have someone who has a relatively high resting heart rate, maybe in the 70s, but who has an extremely strong dive response and who has really strong bradycardia. And we might not really understand the connection between the two or the lack of connection between the two yet, right?




Yeah, if you have a low heart rate, a low resting heart rate, it can imply that you have a lower oxygen consumption than someone that has a higher heart rate. There is a good correlation between the oxygen consumption or the metabolic use of oxygen with the heart rate, but it’s not one-to-one. So if you have one diver that has 70 bpm as their resting heart rate and another has 60 bpm, you cannot say that the guy with a heart rate of 60 bpm is saving more oxygen.


And in the end, you need to save oxygen when you are holding your breath, not when you are breathing, because when you are breathing you have oxygen. So what is more important is how your heart rate is behaving when you hold your breath instead of how it is when you are not holding your breath. Now, even in other sports where we used to correlate the heart rate with the oxygen consumption, now it’s clear that it’s not the case in everyone.


So sometimes the heart rate can underestimate or overestimate the oxygen consumption. So saying that a higher heart rate means that you are using more O2 and a lower heart rate means that you are using less oxygen while breathing is not completely accurate. It could be true in some people, but not everyone.


But when diving, it’s even more difficult to determine. And a lot of groups have tried to measure oxygen consumption while holding your breath. But it’s very difficult to do it because we need the exhaled gases to measure the oxygen consumption.


So now the studies that have been done in the past, they measure gasses in the beginning and at the end of the breath hold. So we have an average of what happens, but we don’t know how the oxygen consumption is behaving during a breath hold. We don’t know if it’s decreasing in the beginning or decreasing in the end.


We don’t know yet. We just know the final result that, yes, when you are holding your breath, you are saving oxygen and the oxygen consumption goes down. But we don’t know when this is happening.


But based on the heart rate profiles that I have seen, I think that the most important thing is to keep it down for a long, long time. And I think there is a lot of differences between freedivers.




One of the things that fascinates me most is the difference between what is happening in depth and what is happening in the static or dynamic disciplines. As somebody who doesn’t really train dynamic or static. Every time I go to the pool and I have to demonstrate something for my students or I have to, you know, do something in the pool, even if I force myself to do some basic pool training, I always feel like I’m kind of back on day one.


Especially when it comes to CO2 response, where I get very early contractions and strong discomfort to rising CO2. But when I dive depth, I have a completely different qualitative experience. I have, even on my deepest dives, 80 meters plus, I still have almost no sense of CO2.


I have something like contractions on the ascent, but they are qualitatively very different to what I would have if I was doing a static. And I’m wondering what you think might be the reasons for that, apart from lack of training. And maybe what the partial pressures of the gases involved could have to do with it, because we often talk about nitrogen in depth, but could there also  be something interesting going on between high partial pressures of CO2, high partial pressures of oxygen, and maybe all three of those gases interacting in ways that we just don’t understand yet?




Yeah, I think you are on the right track there. As you said, when we are diving in depth, we have an increase in the partial pressures of the gases that we have in the blood. So, the deeper we go, the higher we have the increase in partial pressures.


Regarding the CO2, it is important to understand that the CO2 builds up very quickly. So when you start holding your breath, you start to peak the levels of carbon dioxide. But after it reaches the peak, it goes up in a very slow way.


So the highest amount of CO2 or the biggest change could be in the first part of the dive. And you know that the contraction is just the relationship between the level of CO2 and how your brain reacts to that level. So it’s what we call the CO2 tolerance.


We have a system, it’s mainly in the brain, that responds to high levels of CO2. So when you have high levels of CO2, there is a trigger to stimulate the respiratory drive. And then when you start to have the contraction, it’s just diaphragmatic contractions.


So the buildup is mainly in the beginning. But also, the body has the ability to store a lot of carbon dioxide. So we can save a lot of carbon dioxide.


So if we are building up, it will not change too much during the dive. I think that the main difference, and you pointed out very well, between dynamic and depth, is that the CO2 has like an aesthetic effect on the brain. So the question is about perceptions.


So if you are having high levels of nitrogen when you are diving deep, and also high levels of CO2. So that can, and I think that’s why we love doing deep dives, because we feel so nice. And I think the tolerance is related to that.


Because in the end, you are having the same amount of CO2. And maybe it’s too early to say, but so far, when we were doing this data collection in Dahab, we were comparing the static apneas with deep dives. And this is something that we haven’t looked at completely.


But so far, we can see that the diving response is very similar during the apnea test and during the actual deep dive. So we believe that the way you react to holding your breath is quite similar. But of course, when you are diving to depth, there is also the exercise, the swimming effort, that it will change a little bit your response.




What you’re basically saying is that I like depth, because I get high when I dive depth!




Yeah, yeah. Right, okay!




In other words, train more pool if you want to enjoy it more.


Okay, super interesting. So, and this is just to sort of finish up the topic of the dive response, but lead us into the next topic, staying on the topic of CO2.


And because when I put out suggestions to the listeners to ask questions, I got many questions to do with how to train CO2 tolerance. But some of the more interesting ones are about some people who are reporting that they experience some kind of contraction on the way down, quite early in the dive. And then that this contraction, even if the ascent is just a small amount, that this sensation dissipates or lessens.


Do you know this phenomenon, and I feel like I’ve had something like this myself, especially when I’m doing the first dive of the session, you know, the warm up dive, I might already start to feel some movement of the breathing muscles as I approach even just, you know, 9, 10 metres, something like this. But then a couple of dives later, I would dive to 80m and not even feel anything like this. Is this just the body reacting to CO2?


You know, this is the first dive of the day. This is a little bit different to what the system has experienced so far today. But how much has the spleen got to do with this?


I often wonder … is the spleen contraction reducing this sensation in subsequent dives? What are your thoughts on that?




Yeah, it’s the contractions, but it’s not only related with CO2. And we just need to see the contractions as the brain telling us you need to breathe. It’s like when the brain is saying you need to breathe, we feel it as contractions.


So the main trigger is the CO2, that’s true. But also the low levels of oxygen. So when you are getting high levels of CO2 and low levels of oxygen, then the contractions can increase, so you feel it a little bit more.


But also we have something that is called stretch receptors in the lungs. So when you have your lungs inflated, the stretch receptors are sending a signal saying you need to exhale, you need to breathe out again, because we are not supposed to have the lungs inflated all the time. So if you are packing, you are over stretching the receptors, and then you are diving and you have compression of the chest.


So that combination of big lung volumes and then pressure from the increased barometrical pressure, that can induce, that can give a signal to breathe. So of course, I don’t have data to back it up, but that’s what I feel is causing the early contractions on the way down. That could be related with the chest flexibility, but it’s mainly related with the change in pressure over the chest.




Yeah, I think the interesting takeaway from what you said there, it seems like what you’re saying is that we know exactly what we’re doing. We know that we have put on a wetsuit, we’ve gone to the Blue Hole, we’ve descended 15, 20 metres under the water, and we’re doing a training session for freediving. But the body itself and the brain itself doesn’t necessarily have this concept that we’re doing these things for specific reasons.


So just like you said at the beginning of your explanation there, your brain is telling you that you need to breathe, might be kind of the best reason to explain that.




But the good thing is that the brain adapts. So if you are training and during your training you have high levels of carbon dioxide, eventually the brain will say, okay, I think this guy can live with this level of CO2, so I can reset my level. I’ve seen that, not only in freedivers.


There is a disease of the lung that is called COPD (Chronic Obstructive Pulmonary Disorder), in which people cannot move the air out of their lungs. So usually they have high levels of carbon dioxide and they live with it. The normal value for CO2 is 35 to 45 millimetres of mercury and they could have 60 and they are living well and don’t feel anything because as they have that level all day long, the brain adapts.


So it increased the trigger point. So if you are training, and that’s the purpose of training CO2, is that if you are exposed to that level, eventually you will move up a little bit the trigger for breathing.




So what you’re saying is that COPD and what causes COPD, like smoking, is probably good for freedivers, is what you’re saying Frank?




No, it’s not good!




Just looking for a headline!




No, because then you will have another problem with the narrowing of your bronchi, so it will be more difficult for you to breathe.




Yeah, yeah, yeah. No, it’s a bit of a joke, but it’s also partly serious because it’s something I often consider having spent the first, you know, between 15 and 30 years old really just smoking extremely heavily and doing lots of other damaging things to my body and eventually even having a diagnosis of early stage COPD a few years ago. But I still seem to be progressing quite steadily in freediving and I’m very curious about what effect the previous damage that I’ve done has on my progression as a freediver and if there are even some reasons that that benefits me in my progression.


But we can leave that for another conversation. So much to discuss here. I just want to bring in a question from Peter about, okay, when it comes to CO2 training and thank you to Vittorio, Peter, M, Maurice, Patreon supporters who have all submitted questions today. You can become a Patron and support the show by visiting


I don’t have time to go through each one and get explanations for each one, but thank you very much for your contributions. A couple more points here on CO2. The traditional method of training CO2, which I don’t think is really traditional anymore because I think doing 45-minute CO2 tables with, you know, long rest times between breath holds has kind of being universally declared to be of very little use.


But what methods do we have, what are the best methods to increase CO2 tolerance in your mind?




Exactly, in my mind, because we haven’t tested that yet. But the most important method is that you keep it up for a long time during the day. If you are just doing a very heavy session of CO2 tables that lasts 20 minutes, let’s just say that probably it will not affect your trigger because it’s a very small amount of time.


So for me, if you need to work on CO2 tolerance, and that was my case, and also I’m coaching two athletes that are related with me, is try to do things during the day holding your breath. So if you are going, you park your car and you’re walking to somewhere else, try to do short breath holds during the day. Or if you are watching TV, try to hold your breath because I think the only way to make a change in your brain trigger is that you are exposed for a lot of time and it cannot be done just with one session.


So even if it’s a very tough session, and that’s another question, how can you define tough? Because nobody measures CO2 on a regular level to see, okay, how high I’m going on this session. So it’s also tricky to say, how should I do the CO2 training.


But for me, you need to to live thinking about how you can improve your CO2 tolerance. And the best way for me is to hold my breath during the day. Of course, I did crazy things like holding my breath while driving.


I don’t recommend that anymore. But if you are just sitting down, if you are reading something, then it’s also a good training for the brain to get used to holding your breath, I think that’s the best way. The amount of the time that you are keeping the CO2 high is what will make a real change.




Right, not the length of a session necessarily, but the cumulative amount of time spent breath holding through a day. So implementing short but regular breath holding sessions into your day rather than trying to do everything in a 20 minute or 30 minute period, three times a week, for example. Back in Taiwan, I used to go everywhere on a scooter and everyone has, you know, a motorcycle.


And what I would do, because when we come to the traffic lights you have like a timer. And usually the maximum amount of time on the timer is like 100 seconds. And it’s hilarious because a lot of people would have this practice of waiting to get to the traffic lights and then holding their breath and doing that all the way to their destination.


But it’s really funny because the air pollution is so horrible. And I often wonder, like, what are the effects of taking a full breath of air while you’re sitting at a traffic junction, you know, in a busy Asian city. But a lot of people did that.


And I’ve often thought about this. And I remember hearing an interview with David Blaine, who also went through a period of doing a lot of breath holding for his pure O2 assisted breath holds. I think he was up in the seven minute or almost eight minute range for non-assisted breath holds as well.


And he was talking about something like this, like every five minutes of the day, he would hold his breath for one minute or something like that. Like he would do it, you know, all the way through the day. And that’s an experiment that I thought would be quite interesting to try myself.


Maybe like, say, every 10 minutes, hold the breath for one minute, have it on a timer, you know, have a few free days where you could do an experiment like that probably would be quite challenging psychologically to get through something like that. What I did note here about how do you measure, how do you measure CO2 levels in the human body anyway? You mentioned something about mercury.


So is there a device that can do that? I know Juani Valdivia mentioned it before, but I’ve forgotten.




Yeah, there are some devices. They are not cheap, but you can measure the CO2 when you exhale. So you just measure it after a breath hold and you exhale into the device.


And then you have the values of the CO2 in your lungs, which is very similar to the CO2 in your blood, because the CO2 moves very easily from the blood to the lung. So measuring the exhale CO2 is a very good way to know how are your blood levels of CO2. Of course, the best way is to measure it directly in an artery.


But of course, that’s an invasive procedure and you cannot do it frequently. But if you are in a freediving club or you are a community, you can get money together and buy one of the devices and use it just to measure how I am, how is my training going.


And that’s something that I still believe, that training should be focused on your physiology. I hardly believe that if you download something from the Internet and you use it as training, it’s going to give you something, because especially with freediving and the diving responses are so different between individuals, you need to know how you are and how your training is going on, based on your real values.




What is the name of this device?




Oh, there is one that we use one that is called EMMA, E-M-M-A (a capnograph). It’s from Massimo, the one that also makes pulse oximeters. That’s one of the devices.


And we have another one that is a clinical monitor that is very portable. It’s called Lifesense. Yeah, but they are quite expensive.


They are not cheap.




Okay. Okay. Let’s see.


A bit of a crowd crowdfunding for this later on down the line. Well, I’m in Dahab. When you come back to Dahab, let me use your device. Okay?




I will!




Okay. So let’s move on to the topic then of blackout, hypoxic loss of consciousness. We know what are the main contributing factors.


I think it’s clear that blackout is caused by hypoxia, lack of oxygen in the brain. The reasons for that are going to be that the diver is maybe overreaching in some cases, or they are experiencing other unexpected conditions in the dive. Maybe the conditions have changed in the water, the temperature, the current, announcing dives that you’re not comfortable with, the added stress in competitions of spectators and anxiety related to performance and things like that.


Can you elaborate on those ideas and also maybe give some of the lesser known reasons why we might lose consciousness during a dive or some things that most people might not be aware of regarding hypoxic loss of consciousness.




Yeah. First, you know, that’s the subject of my thesis, so I cannot give too much here, but I promise you that I will send you the link. Probably I will make my defense on April and I can send you the link and you can see the actual defense of the thesis where I will go a little bit deeper on what I have found.


But I can give you some food for the mind about the blackout. We know that we need to have a very good equilibrium between the amount of oxygen that we have in our body and how much are we using the oxygen. So that’s the simple way to put how we will get into extreme levels of hypoxia.


So that means low levels of oxygen in the brain cells, which is the most important in the end. Because we can have low levels in the muscles, but we are not going to faint from it. But if we have low levels of oxygen in the brain, we will faint.


So yes, what you said is true. If you have small lungs, small spleen, and no myoglobin, then your oxygen stores are small. If you have big lungs, big spleen, a lot of myoglobin in your muscles, normal haemoglobin, then you will have a lot of oxygen stores.


So that’s good. But also, how are you using the oxygen? So as you say, if you are afraid or nervous, then you will be using more oxygen.


If you have a current, then you need to kick more, and then you will use more. If you have a poor diving response, then you will not save oxygen, and you will be using more. So even though you have very good or very big lungs, if you are using too much oxygen, that’s also bad.


So the best combination is to have big oxygen stores, but also have a strong reduction in oxygen consumption while diving. That’s the first thing to avoid the blackout. But on the other hand, we have the values.


We have the values for fainting at altitude. So we know, okay, when the arterial pressure of oxygen is below 50, then there is a high risk of fainting. But in many studies, the oxygen has been recorded, and it was extremely low, but people were conscious.


So I don’t think it’s the only thing. The hypoxia is the main thing, of course, but it has to trigger something that makes you lose consciousness. That’s my idea.


And also, we need to think about hyperventilation. Hyperventilation has several effects. The main one is that it reduces the CO2 in your blood.


So you will have a later warning of when you need to breathe. But I think this is more important on snorkelers and recreational divers than for competitive freedivers, because we usually have a very good safety setup. So I don’t think it’s a big problem.


But there is also something that you need to think about, that is when you are breathing, you are using oxygen because you need to move muscles for breathing. And if you’re breathing too much, maybe you are using too much oxygen with your muscles. So that’s why it’s what we call the cost of breathing, because just by breathing, you are also using oxygen.


So a very forceful way of breathing can increase the oxygen consumption just before diving. So you will start a dive with a higher than usual oxygen consumption. That’s why relaxed breathing is more important because you are not consuming as much oxygen while breathing.


So yes, that’s my shorter version of what I believe are the important things on blackouts.




What I’m thinking about is how oxygen consumption is affected by fasting, by the food that you’ve consumed, the difference between your carbohydrate consumption and your fat consumption, your carbohydrate, your glycogen use, whether you are in a more ketogenic state. 


I hear that some static athletes are using extreme fasting before a competition, for example, to induce muscle wasting so that they’re not using so much oxygen during a static attempt. But for the more active, maybe the depth diver who still has to maintain a certain level of athleticism and physical strength during a dive, what dietary protocols would be working best for free diving?




That’s a very good question. It’s how we can reduce the oxygen consumption naturally because we can reduce it even with medications.


But of the main ways to reduce the oxygen consumption, as you say, one is fasting. Fasting is known to reduce the oxygen consumption. And the problem is to know how much, because when you are fasting too much, then you are getting rid of the carbohydrate that you have mainly in the liver, but you use it very quickly.


Then you go to fat. And that’s why intermittent fasting gets rid of fat. But when you don’t have that, then you will start to use muscles.


So you will lose muscle mass. And that’s a state of catabolism that in the end, as you say, is bad for performances. So then there has to be a balance.


Also, when you are using carbohydrates as the main thing in your food, the carbohydrates produce one, let’s say one molecule of CO2 per one molecule of oxygen. So that’s what we call the respiratory quotient, that is how much CO2 I am producing for one molecule of oxygen. So it’s one to one.


When you are based on proteins and fat, then the radio is 0.7. So it means that you are producing less CO2 per oxygen, but it comes at a cost of you need more oxygen to produce the same level of energy. So when you are based on carbohydrates, you are using the most efficient way to use the oxygen to produce energy that is in the end why we use it. When you base are based on fat, you know, the paleo diet, or a diet that is mainly proteins, then you will have less production of carbon dioxide, but you are expending more O2.


You need to use more oxygen to produce the same amount of energy. So the answer is, it’s difficult to find a good balance. Yeah, for instance, I will say, when you are facing a depth competition, and you are intolerant to CO2, or you are prone to lung squeezes, and, you know, have heavy contractions at depth that are related with lung squeeze, then you can try to remove the carbohydrates just before the competition.


I don’t know the time, 10 days, one week. We haven’t tested that yet, but it’s a good way to try to keep a balance close to the effect that you want. That Iyou want to get rid of CO2.


If CO2 is not a problem, then probably it’s better to keep on a high-carb diet, energy-wise.








Okay, that’s the fasting. Also there is temperature. When you are in a warm environment, that will increase the oxygen consumption.


When you are in a cold environment, or exposed to cold, you reduce the oxygen consumption. And I think life is like that. You cannot have both things.


So, I don’t know if you remember, it was maybe 10 years ago that, you know, the movement of no warm-up dives, extremely cold dives, or diving without wetsuits, to induce a strong diving response. There was also a good physiological side to diving with a little bit of cold, to be with low levels, to reduce your temperature, to reduce the oxygen consumption. But it’s a very thin line between having the nice effect, which is to reduce the oxygen consumption, but if you are getting too cold, then you will start to shiver, and that will increase the oxygen consumption again.








But at least, and that’s something that I recommend for other reasons also, I think it’s good to not be so comfortable when you train. We are used to the wetsuit, but I think that during training, if you are experiencing a little bit of cold, it can have a very good effect on how you react to be in cold water, so you don’t need too much isolation. And it can give you the edge to dive a little bit colder than usual.


And also, there is another effect on myoglobin, so when you are exposed to hypoxia and cold, at least on animals and seals, that can increase the level of myoglobin. So cold is another way to reduce oxygen consumption in a natural way.




That’s so fascinating. And every time you mention myoglobin, I always want to steer down that path and get into that a little bit. But I think that considering the length of time that we have, we’ll try to stay a little bit more on the topics that I have here.


And let’s move on to the last topic that I think is the most interesting, that most people want to dig into. You said that in the past, you had such an issue with lung squeeze that you ended up out of the sport for five years. Perhaps you could just explain what was going on there, at what depths were you squeezing, how were the squeezes presenting themselves, and what was the strategy that you eventually came up with to manage the squeeze?




I started to have lung squeezes very much related with heavy lung stretches. I was doing lung, you know, the thoracic stretch with full packing and also with reverse packing. And I noticed that that was very close to giving me lung squeezes.


As I told you, I grew up in on island and I was diving there almost, yeah, it’s three times a week. And I never had any squeeze at all. And I was getting, sometimes I went eight metres more than my PB by mistake and I blacked out, but I didn’t have any squeeze.


So I never knew about that until I moved to another city that was on the mainland, far away from the sea. So I was worried that I would lose my ability. So I started to do the heavy packing stretches and reverse packing stretches and doing empty lungs dive in pools.


Nowadays, I don’t recommend that. I think it was related. And when I had my squeezes in the beginning, it was 40, 42 metres.


And mainly, I was coughing a lot of blood, not small amounts. It was huge amounts of blood. And so when I had it, I stopped, of course, for months.


And then I get back and I start to train on lakes that were at high altitude because I was living in the capital city of Colombia, which is Bogota. And it is almost, it’s close to 3,000 meters over sea level. So I was training in lakes there.


And my final lung squeeze was in a lake and I was diving to 10 metres, just 10 metres. And I said, okay, I’m done. I need to get out of this.


But I decided to have a real approach to the problem. So the first thing, and I always recommend that if you have lung squeezes, you need to rule out some physical stuff that you have. For instance, I had high blood pressure.


And high blood pressure is a risk factor for lung squeezes. So I needed to normalise my blood pressure. But also, if you have problems in your heart, in your valves, or if you have some congenital problems in the arteries of the lung, then you will be prone to have lung squeezes.


So the first advice is that if you’re having lung squeezes, you need to get a proper check out with someone that knows how to look for real, for reasons that are not related with the depth. Because if you have in the lungs or in the heart, or in the kidney, you can have pulmonary edemas and you are thinking it’s always the depth, but it’s not. It could be other stuff.


And then when I had my blood pressure normal again, and everything was okay, I start training again. I was training for a freediving competition in Greece, I remember. And everything was going well.


I went to the island for a depth training season. It was 10 days previous to the trip. And during that training, I had the most severe lung squeeze that I remember.


And it was at 43 meters. And it was in an incredible amount of blood that came out of out of me. It was unbelievable.


And I was wheezing, and I couldn’t breathe. And that took me almost a week to be breathing normally again. So when that happened, I said, OK, of course, I didn’t make the trip.


And I started to dig a little bit into the real problem of the lung squeeze. And this is my approach. And I will, I will just share it.


The first thing is to understand why, what is the lung squeeze? And to put it into layman’s terms, you are getting blood inside your alveoli. And in your alveoli, you are only supposed to have air.


So you are producing blood. Or in the less severe cases, you have liquid. But, and that’s one of the big differences compared with the other kinds of pulmonary oedemas, is that a lot of freedivers, they have this blood.


Some people are just having like a froth, a little bit of pink froth. But a lot of people have a lot of blood. So it means that that blood is coming from the lung capillaries.


There is no other way, it is coming from the lung’s capillaries. And the forces that, you know, keep the blood in the blood vessels is, one is what we call the hydrostatic pressure. So it’s the pressure inside the capillary.


So everything that increases that pressure can make the capillary break. And there is a lot of things that can do that. I remember that a freediver, she asked me for some advice on lung squeezes.


And I wrote her like 40 different things that you need to do, because it’s a lot. So what can increase the pressure? One thing is hypoxia.


And there is a reflex that you have that is called the hypoxic pulmonary vasoconstriction. When you have low levels of oxygen in the lung, the arteries get extremely constricted to avoid sending blood to that place and move the blood flow to places that have oxygen. But some people have a strong pulmonary vasoconstriction, too much. And that will increase the pulmonary pressures, producing pulmonary hypertension.


So high blood pressure in the pulmonary artery, can, of course, break the capillaries. It’s something that we call stress failure, when you have a huge increase in that pressure. Also, the capillaries in the lungs, they can be extremely constricted if you are lung packing, because we have some capillaries, that when the alveoli is too big, they are compressed.


So when they are compressed, the resistance increases. And also, the resistance increases when we have extremely low lung volumes. So that’s why training on residual volume is not good.


I recommend training on functional residual capacity, which is the neutral state of the lung and gives less resistance in the pulmonary artery. So that’s the ideal state. Also, technique, because if you are exercising too much, you are increasing the blood flow, and you are increasing the cardiac output, and increasing the cardiac output also increase the pulmonary pressure, so that can break up the capillaries.


This is just to name a few. And the other side of the balance is the pressure on what we call the interstitium. So it’s all the tissue that is surrounding the capillaries.


When we are breathing, we have negative pressure. So that in the end is the difference between the capillary and the outside of the capillary that makes the pressure difference. So anything that reduces the pressure around the capillary will also increase the possibility for the blood to come out.


And contractions is the main thing. Usually when we are breathing, the pressure inside the pleural space, you know in the pleural spaces, we have like a thin layer that covers the lung, and another thin layer that covers the thoracic cage, and between them is what we call the pleural space. It’s like a virtual space because it is almost nonexistent.


It has about one millilitre of liquid. But if we are having heavy contractions (usually the pressure there is minus five millimetres of mercury), but when you are having contractions, it can go to minus 30, minus 35.


So that’s a huge difference in pressure that can induce the movement of blood out of the blood vessel. Also, and this is something that nobody thinks about, that is the shape of the lungs. The males have our lungs shaped more like a pyramid.


And in females, the lungs are shaped more like a cylinder.




We (males) have a huge vase and a very small apex in the top.







Yeah. And the biggest thing there is the relationship of the two layers of the lung pleura and the thoracic pleura. You need to imagine like if you have two sheets of glass, if you put water in two sheets of glass and you try to, you can move the glass together.


But if you try to move them apart, it’s very difficult. So when you have a difference between the thoracic pleura and the lung pleura, you will have a bigger or greater negative pressure. And that’s the difference between going with the head down or with your feet first, that will make also a difference how the pressure is changing on your lungs.


That’s something that I would like to test in the future, and probably next year when I finish this, that’s something that I will dig into, is the difference in shape. And it can increase the negative pleural pressure. So I could talk about this almost for hours, because another issue is the amount of blood that you have in the chest.


As we mentioned before, the blood shift increases the amount of blood that you will have in the chest. And the blood vessels in the lungs, they can hold a lot of blood. They are designed to be that way, because they are flexible.


So you can put a huge amount of blood without any problem. But it depends on each individual person. If you maybe have more stiff arteries, then you cannot hold that much.


And, you know, over-hydration is something that I think is also important. You know, drinking too much water, more than you need, it can increase your blood volume. And, you know, if you have too much blood in your chest, then that’s another risk factor for it.


Another risk factor is the rib cage compliance. So how flexible is your chest? And it’s very easy to imagine.


If you are going down, your lungs are reducing size, but your chest also needs to reduce size by the same amount. So if your lungs are reducing faster than your rib cage can do it, so if you are very stiff, then you are getting a greater negative pleural pressure. That is also the problem.


So anything, age, the lack of flexibility, cold, if you are exercising too much, the thoracic muscles, they are stiff, so that will increase the stiffness of your chest. If you are wearing a stiff wetsuit, if you are afraid or you are fighting with equalisation, everything that puts stiffness on the chest can increase the risk of having a lung squeeze. And also alcohol, because I found out that in almost 80% of the dives that ended up with a lung squeeze, I had wine the night before.


And wine is kind of similar to aspirin and everything that makes your blood a little bit thinner that affects coagulation can have an effect on lung squeeze. And there is a paper with not too much participants, but they found that of the spear-fishers that were taking aspirin, they had more lung squeeze than spear-fishers that were not using it. So yeah, I can take four hours and I don’t know, maybe I can send you like the paper I sent to the freediver with my step-by-step approach to avoiding lung squeezes because most of the things were before the dive and some were during the dive.


(This paper that Frank mentions is available in the article section of the Freedive & Thrive website at




But you said that in your case, the strategy, because you had very serious lung squeezes, how did you get back to diving then? Was it just the alcohol the night before?




Not all, it was a lot of things. It was a huge program for me because I wanted to go back to freediving.


And as I was living on the mainland, I couldn’t train depth frequently. So I needed to be able to get ready for a competition in five days. And my last competition was maybe five years ago.


And I was able to train just five days and went to 60 meters completely okay. Because I think that you shouldn’t believe that lung squeezing is part of the game or it’s normal. It is not normal.


And it has chronic effects on your lung health.




Yes, yes.




So if you are like, oh, this comes with the game… I just, I know that everyone had it, but it can have a long-term effects on your lungs. So it shouldn’t be seen as normal.


So what I did to avoid lung squeeze, I removed lung packing and reverse packing from my training. I started to do pool training only on FRC and static. Almost all my training was on FRC, all the time.


And I trained the CO2 tolerance to reduce the contractions and did daily stretching of the chest. I then removed all the thoracic exercises at least 10 days before deep diving. And one of the biggest thing is to warm up.


I noticed that when I was doing specific procedures on warm up, I was lung squeeze free. So I made that like a rule, I have to warm up in this way. And usually after several days of diving, the warm up can be reduced, at least for me.


In the beginning, it’s quite long, but close to the end, it’s a very short warm up. And the warm up is just to make the chest a little bit flexible. It’s not about your skills or your ability, it’s mainly to keep the pressure on the chest.


And also it’s about trying to do depth training frequently. So when I came back to the lakes, I was doing, I tried to do at least one week of depth training with full lungs. But I can do that, I can send you the document with the approach that I used, that worked in my case.








But it was based on physiology.




Okay, excellent. Please do that. Okay, Frank, I have so many more notes here than I expected.


I’ve been taking them all the way through this discussion and we don’t have the time to go into too much of them this time. Maybe we can do another session down the line where we can expand on some of these ideas or look at other topics. But just to finish up, I just want to ask you, if you had an unlimited time and unlimited funding, what do you think are the most interesting and exciting areas of freediving for further research?


If you were kind of like the, what’s his name? Iron Man, Tony Stark, whatever his name is. If you were obsessed with freediving and had these kinds of resources, what would you do?



Yeah, I would like to do more research on the lung squeeze. And especially we need to develop some devices even to be able to do measurements during deep dives. I think you see in a preliminary state of some researchers in Italy, they are using ultrasound machines in the water.


And I think that’s a clever approach because we need to have more information about what is going on during the dive. We know a lot of things just by guessing and by physiological models, but I think we need to find ways to actually measure, for instance, what is happening with the blood pressure in the pulmonary system during dives. And the research on lung squeeze needs to be more structured.


And yeah, as I told you before, I had some conversations with AIDA a long time ago about that, that we need to have a very straightforward approach and to have a very good registry of people that are squeezing. I think that’s the beginning to understand the problem a little bit. But yeah, the quick answer will be that I would like to be more into the physiology of the lung squeeze.




Well, I hope you win the lottery or otherwise find the funds to do that kind of research.




Or find funding, yes!




It’s such a fascinating sport that we’re involved in here. I could completely understand why we don’t have the access to those resources, but at least we can do our best to provide this kind of information through the podcast and wait patiently for the data to emerge. Oh yeah, I forgot the most important question in the podcast that I always ask the guests.


Why do you freedive?




Why? Because I love it. No, it’s as I told you, it was since I was a child.


I was by the sea all the time and I just love the sea. That’s something that I miss now because I’m living in the north of Sweden. But I have a lake, so at least I’m not so far away from water.


But yes, I freedive because it’s the feeling. It’s a very nice story. My mom is very religious and she was always complaining that on Sundays I didn’t go to church because I was freediving.


And she said, oh, you need to go to church to find God. And I told her, I find God when I’m diving. I feel more connected with my world and the animals and I feel like I belong when I am diving.


And freediving is, because I also did a lot of scuba, but it’s not the same. It’s like you are on your own. It’s your own body.


You don’t need anything else. It’s what I say, it’s almost a religious experience to freedive. That’s why I do it, it’s because I love it.




Amazing. So the ocean is your church. Fantastic.




Yeah, that’s it.



Frank Pernett, thank you so much for joining me here in The Freedive Cafe to discuss freediving science. It’s been a very, very interesting conversation.




It was a pleasure.




I have so many more questions now. Have a lovely rest of your day and I hope to see you again soon in Dahab, where I know you do come. So you’re always welcome and maybe I’ll see you in the water.




Thank you, Donny. It was a pleasure. And yes, anytime. I would love to do it again.

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