Heat Stress Challenges in Ultramarathon Events with Nicolas Bouscaren and Sebastien Racinais | Koopcast Episode 76

trail and ultra runners what is going on what's happening i'm really excited everyone is here with me today welcome to another episode of the KoopCast as always i'm your humble host coach Jason Koop and on the podcast today we have the dynamic duo of nicholas bossarin and sebastian hasinas to discuss all about how heat stress affects the body and how that heat stress is different in marathons versus ultra marathons their recent paper which is titled heat stress challenges in marathons versus ultra endurance running it caught my eye as it has this insightful infographic contained within it that beautifully and simply illustrates what athletes should be watching out for in these different events a link to that research will be in the show notes nicholas is a researcher and medical doctor in of all places reunion island where the infamous diagonal day do diagonal day food that's what i meant to say is held and that is one of my bucket list races i cannot wait to have the opportunity to do that particular race this paper that actually caught my eye was nicholas's PhD thesis and his supervisor sebastian hasinas who's the head of research at aspatar university in qatar he also wanted to join in on the conversation so let's line this up a little bit if you can't tell we have two academics who both live in really hot

places they are runners themselves so i'm sure that they are living every last bit of the research that they produced a little bit of a note before this podcast starts english is not nicholas's first language but he was gracious enough to give this interview a go and i appreciate the fact that he stuck his neck out there a little bit to give us some more information on heat stress i promise you the content is worth it so i'm going to get right out of the way here's my conversation with nicholas and sebastian all about heat stress and ultra endurance events first off i i appreciate you guys being on um it's always hard to it's always interesting to coordinate these you know like it's just uh we're obviously coordinating things from all over the world but first off uh sebastian where you come where you where you coming to us from so i'm a french originally from the south of france from montpellier in the south of france but i left france 20 years ago going uh to guadalupe for uh three to four years and now i've been located in catar in middle east since 2007 so for 14 years now excellent and nicholas where are you coming to us from okay i i come from toulouse in south of france too but uh i am in reunion island for six years now i think uh trail running heaven and also uh yeah yeah it's very great the trail running

out there is fantastic and also more pertinent to this conversation uh you guys get copious amounts of heat and that's what we're going to talk about um so nicholas you're the this is your PhD uh research correct that we're gonna that we're going to discuss yeah okay perfect yeah um first off like what inspired you to do that and i'm guessing it has something to do with where you live but your your PhD research centered around the differences in the heat that athletes experience in a marathon course compared to trail and ultra running settings what inspired you to do this research in the first place to answer this question i think first i have to explain why i started working on termovulation physiology in ultra endurance running and and i've been living for reunion island for six years now and this island is a french overseas department the small iceland of 2500 kilometer squares which is located in the southwest of the indian ocean near to south africa and precisely near at the east of madagascar this iceland is classified as unesco world heritage site since 2010 and in this small area you are like the diversity of a continent it's incredible there are three calderas

around the summit of indian ocean the piton des neiges at 3070 meters one of the three calderas can only be reached by helicopter or on foot there is like 20 peaks over 2000 meters a large part of humid forest on the east of iceland coral reef and lagoon on the west and probably the most one of the most active volcanoes in the world on the source the piton de la fornaise and this diversity is like the perfect playground for trail running there is each year over 120 races organism and almost than 20 000 runners who participate at the end of the october take place probably one of the most famous ultra races in the world the grand red de la réunion which brings nearly 6 000 participants over three trail formats of races 65 kilometers and the most important the most famous probably la diagonal des fous which crosses all the island from south to north over 165 kilometers with almost 10 000 meters of essence but despite this

this paradise environment the difficulty of running on the diagonal des fous is that this island has a tropical climate you can therefore frequently run in temperature of around 25 to 30 degrees and with very very high humidity levels of over 70% to 80% so given the importance of tri-running on reunion iceland i naturally start tri-running at a very very high level when i arrived on the iceland and i was quickly confronted with this difficult environmental conditions as a scientist and the sport physician i wondered about the physiology of thermoregulation i searched the literature and from that a lot had been published about the repercussions of it during sports unfortunately this publication were almost exclusively limited to endurance events up to the marathon and then professor sebastian racine who may know a little and who had done a lot of work about thermoregulation physiologists suggested that i started a PhD on the physiology of thermoregulation in neutral endurance running and then this article is the first step of my walk and was to identify what are the differences that could be found

between marathon and ultramarathon which could impact in a positive or a negative way the physiology of the organism during a race in horse environment and on this paper we asked if there are any specificities in ultra endurance running that could disturb or challenge the knowledge we have on thermoregulation physiology that come either from laboratory studies or from walk on runners of classical endurance events and so and so like like like many researchers you're taking a personal experience of having to run on reunion island and saying i want to learn more about this this is so hot it's so hard for me i want to learn more about this and apply it to my PhD research and in the paper in question i'm going to provide a link to in the show notes so everybody has access to it and first off you have good really good and very uh understandable infographics that are associated with the paper i think everybody really appreciates that but let's start by just outlining the major thermoregulatory differences between a marathon and an ultra marathon because they're more than more than meets the eye and they're not a lot that's and people are somewhat surprised or they're not a lot of different and people are somewhat surprised or they just don't think about it as much so what are those major differences nicholas i think to understand the main differences it is important to review and to totally understand the physiology of the thermoregulation during exercise how does the organism fight against it what is important to understand is that the main thermal stress

the energy that is not only be evocative is not linked to be evocative is not linked to the environment but to the runner himself indeed 20 to 25 percent of energy released by it wrote hydralizing of atp adenosine trifosphat the fuel of organism is using for muscle contraction that is to say about 70 percent 75 percent to 80 percent does not contribute to external work to muscle contraction contribute to external work, to muscle contraction, and is internally released as heat. This metabolic heat production needs to be dissipated to the environment to limit the increase in cold temperature. This can be done by direct radiation, where the body dissipates heat in the form of infrared radiation to cool an object or surface around it.

Heat can also be dissipated by convection and conduction when the air temperature is colder than the skin. And all these phenomena like conduction, convection, and radiation are extremely limited when exercising warm or hot environment. And if radiation and convection are zero or negligible, the only way for the athletes to thermoregulate is through evaporation of sweat. It is important to precise that it is not the fact of sweating that allows the athletes to thermoregulate, but the evaporation of the sweat produced. That is a change from the liquid state of the sweat to the gaseous state and this transformation.

This evaporation consumes energy, which is thermal energy. So in humid environments, which limits the evaporation of sweets are much more restrictive and much more limiting to performance than hot and dry environments. Okay, then one last point. Heat is produced in the muscle and must be evacuated through the skin for evaporation. It must therefore be transported from the muscle to the skin in order to evaporate into the environment. An analogy with your car is a perfect way to illustrate this. In your car, the engine produces heat. This heat is dissipated into the environment at the radiator at the front of the car.

The cooling liquid carries this heat from the engine to the fan of the radiator and back again after being cooling to the engine. In the human body is exactly the same thing. The engine that produces heat is muscle. The radiator at the front of the car is the skin. And the cooling liquid that transports the heat is the blood. This implies that when exercising in a hot environment, there is a redistribution of blood flow to the skin to optimize thermoregulation and evaporation process. This means too that stress represents a kind of cardiovascular stress. This blood redistributed to the skin does not participate in the cardiac refilling in the same way as the blood that is addicted to the muscle.

There is therefore a decrease in what is called the systolic ejection volume of air. That is a blood ejected by the air at each contraction. It will be compensated for by an increase in the air rate. This means that for a given exercise at a given intensity that requires a given cardiac output, the air rate will be higher in a hot environment than in a neutral or temperate environment. We must therefore consider heat stress as a cardiac stress. Except that, as you know, the increase in air rate is limited. And therefore, when the intensity is increased, there is a decrease in cardiac output and therefore a decrease in performance, which is linked to the production of metabolic heat.

Okay, sorry. That's a very long introduction to answer your initial question. But I think it's very important to understand all the paper. This is perfect because, and I'm going to set this up for the differences that I know you want to dive into in a second. But the fact that we as humans have different ways of dissipating heat starts to explain why marathon distances need to be treated differently as compared to ultramarathon distances when we're thinking about how to thermoregulate correctly. So let's get into the second part of that question, right? These fundamental differences between the thermal stress that an athlete is going to experience during a marathon versus the thermal stress that they're going to experience during an ultramarathon.

About metabolic heat production during ultra-endurance running, Hell running and the use of trekking poles increase muscle recruitment and impair running economy, consequently resulting in increased heat production for a given running speed. Furthermore, the low running pace and the long section of walking during ultra-endurance running limits self-generated wind velocity and convective cooling when compared with marathon running. However, as we have seen, the main factor for heat production is exercise intensity, and longer events may be less prone to hyperthermia in a given environment as they are performed at lower intensity.

The metabolic heat production is then therefore a rather protective or less deleterious factor in the limitation of performance in relation to heat in favor of the ultramarathon running over the marathon running. Okay? Yeah, I got it. So let me kind of recap that. And I think this, once again, sets up kind of the conundrum with ultramarathon running. Because the intensity is lower, you are not in an ultramarathon setting, you are not producing as much metabolic heat. But paradoxically, because the intensity is lower, also the speed is lower.

And so the wind that is helping to evaporate the sweat off of your skin, which is part of one of your cooling mechanisms, is not as great. So you have this yin and yang effect where the intensity is not contributing to the thermal stress as much. But the fact that you're going slower actually does contribute to the thermal stress in an ultramarathon event. It's perfect. Better than my explanation. Yes, Sebastian, please. If I may, we should also consider the duration of the event. One of the main differences between marathon and ultramarathon is duration and intensity of the event.

And for a long time, for decades, we have been considering the duration only. Because most of the studies in thermal regulation have been done with militaries or in occupational setting with a more constant load model. So for a long time, we thought that the duration was a misfactor. So that ultra-endurance athlete may be at a higher risk than endurance athlete. But it turned out that when you work with athletes, it's different than working in an occupational setting. When you work with athletes, the main risk factor is the intensity. And that's something that became very clear, notably after the 2016 Cycling World Championship. We made some measurement of temperature in some of the elite athletes participating to the world champ. And we saw that actually the same athlete could reach higher temperature in a time trial, that is a race of 40-45 minutes, than in a road race.

A road race is three hours for the women, six hours for the men. So it was clear that for the same athlete, actually a shorter race was actually at a higher risk of reaching high temperature than a longer race. Hence, this question about marathon versus ultra-marathon and the reason why we start this series of work. Yeah, and this actually came out, you guys are probably not aware of this. This actually came out in an earlier, actually two earlier podcasts, now that I'm thinking about it. One of them with Alan McCubbin out of Australia, and the other one with Stavros Koros, who's here in Arizona. And one of the things that they mentioned is your body can tolerate these extreme internal temperatures for a very short amount of time.

And if you're in those situations, certain cooling interventions make more sense than other cooling interventions in a situation where you're exposed to the heat for a long period of time. And the one that came up was a menthol mouth rinse. Which is becoming more and more popular at the shorter events. Because what it does is it tricks you into thinking that you're cooler, but it doesn't actually reduce the thermal stress. So if you're in the situation like, Sebastian, you were mentioning earlier, like a time trial situation where the event is only 40 minutes or 60 minutes. And you can tolerate a high amount of thermal stress for a short period of time. That menthol mouth rinse might be a good intervention because you're just tricking your body into thinking that it's cooler.

But if you're in a longer event, and we're talking about ultramarathon, this is why it's not a good application in an ultramarathon event. If you're in a longer event where you can't tolerate that amount of thermal stress because of the duration, that type of intervention is probably counterproductive. Because eventually, you're going to not be able to tolerate that high level of thermal stress because of the duration of things. I just wanted to comment on the menthol because now it's quite a fashion intervention and everybody's talking about menthol and so on. I have a bit of a different opinion that most people on that. As you said, menthol is just a perceptual intervention. It will not change your thermal regulation at all.

So that means if somebody, as me, with just an amateur runner, go for a run in a heat, I don't feel very well, I slow down. If I take some menthol, I will probably feel better. I will probably go a bit longer or a bit faster. But when you look at elite athlete, the response is totally different. An elite athlete that is running to win a race is already motivated. He's already at the limit of his physiological capacity. And taking or not taking menthol will not change anything to his performance. And we did a questionnaire very recently during the Doha World Championship, during the road race, that we're in hot ambient condition. And 1 to 2% of the athletes only were using menthol for pre-cooling or for mid-cooling.

So it's really not something so common in elite athlete. This is more for amateur athletes. Yeah, that's a really interesting point that you bring, that the elite athletes are already highly motivated. And that trick, because it is just a trick, is not going to be as effective for them. I appreciate that insight there. I'll put links in the show notes to those two podcasts because we did discuss that aspect. But, Nicholas, I kind of want to get back to the dialogue here and talk about something that is very unique to ultramarathons. And this is the duration. And we know that duration affects athletes in a number of different ways. But one of the ways, particularly in an ultramarathon setting that makes it unique, is that the duration provides the environment an opportunity to go through these big cycles of hot and cold.

And if you think about a normal ultramarathon race, it starts in the morning. It's usually cold. It's not in Europe for whatever reason. They wanted to start all these races in the evening in Europe. But most races in the U.S. will start in the morning where it's relatively cold. It'll then go through the peak of the afternoon, which is the hottest time of the day. And a lot of athletes are then finishing in the evening where it's very cool. This changes the way that athletes can approach their thermoregulatory strategies. Why don't we talk about the complexities of that and how it relates to the paper that you produced? This is an interesting question, but one that has been little study to our knowledge in the literature.

I will therefore be relatively brief as this or just assertion in source. But how can being confronted with large variations in temperature and altitude have a specific influence on thermoregulation? That is the question. The first thing that can be said is the temperature variation are important. And specifically in region Iceland from zero degree to 30 to 35 degrees, but not major on ultra-endurance races. We rarely encounter temperature below zero degree, which creates a relative physiological constraint. It's not being confronted with minus 10, minus 20 or minus 30 degrees.

The second thing, and this was discussed on the paper, is that cold temperature expedition requires the carrying of equipment. And very often this is compulsory on the races. Warm clothes, gloves, and raincoat to anticipate change in environmental condition. This can act as either a protective measure in relation to heat by reducing direct radiation, for example, or as an aggravating measure by inhibiting evaporation or increasing the waste to be carried, and therefore the production of metabolic heat.

The last, but not least thing on this part of creation is more about preparation and chronic adaptation of athletes. It is important to note that the best counter-missure that can be practiced fighting against it is acclimatization and training in the heat. It is indeed recommended before a race in hot environment to train in natural hot environment or in laboratory to protect health and improve performance. This allows for fixed intensity to reduce the health rate, to decrease the skin and central temperature, to increase the sweat flow, and therefore to improve the walk capacity.

However, some athletes fear that heat training will have deleterious effects during temperate race or during passages in cold environments. Rest assured, there is no deleterious effect of heat training on performance in temperate or cold climate. Either it will have no effect or it will have a positive effect. So if there is a slightest chance or risk of heat picking oats, it is essential to train in the heat before a nutrient endurance running. And what, Nicholas, can I ask you, what are the limits of that? Because a lot of athletes will take that as, I should train in hot environments all of the time.

Because if you present this proposition that it's either neutral or beneficial, they'll say, well, I need to layer up and run in my down jacket or run in my long sleeve shirt to increase the thermal stress in a, not in a natural way, but in an unnatural way. So in your estimation, what are the limits of that? I mean, should athletes be going out and seeking hotter environments and contriving things to run in hotter environments based on, you know, based on that strategy? Oh, sorry. I think I need help. Yeah, that's fine. Sebastian, you want to jump in there? Thank you. Sorry, Jason.

There will be two parts in my answer. The first one is that heat training is a stimulus of any other one and it needs to be planned in your training year. So in the same way that you will go for an altitude training camp, for example, you can go for a heat training camp. You will not run only up heat, you will not run only down heat during the year. So you will also not run only in the heat. If you were only training in the heat, that will impact the training intensity. Because after a couple of hours, for example, or after even 30 minutes in the heat, the thermal stress, that is a cardiovascular stress, as Nicolas explained previously, will reduce your absolute training intensity. So you do not want to only run in the heat.

That's the first part of the answer. The second part is planifying your training is the same for any type of training. You cannot be at the top all of the year. So you plan generally for one or two major races during the year. And your training is done in a way that you will have some hard training period, then you will have a taper, and then you will reach your peak at the time of the race. That's the same thing for the heat adaptation. If you want to maintain it constant for good the year, then you will have an average level of adaptation all the year as you can have with your fitness. But you have to manipulate it in the same way you manipulate your fitness by trying to reach a peak of adaptation at the time of the race. I love that. That's a great answer, Sebastian, because I don't want athletes to come away with this and say, oh, I just need to train in a hot environment all the time.

Your point that you need to periodize it strategically is very well taken. And one of the things that we all recognize here and the audience should understand is that any of these heat acclimation adaptations that we're seeking are relatively acute. They happen in very short time frames, and they also kind of go away in very short time frames. It doesn't take a lot of dose to achieve it. But it's not like you have to spend four or five months in a hot environment. Those adaptations happen very quickly on the order of days or maybe even a week versus the typical endurance adaptations that we're looking at, which take months or years to really manifest.

So that is a really good point that periodizing heat interventions throughout the year is a very smart way to go about it. That's correct. In terms of timeline, just you will need one to two weeks of training in the heat in order to gain the adaptation. And you will retain some adaptation for up to one month after your heat training block. Yep. Very good guideline right there. I think that illustrates it really well. Okay. So, Nicholas, we're going to get back to you because one of the other things in the paper that I thought was really interesting were this cascade of effects that can stem from dehydration and or poor hydration combined with thermal stress because it's not just overheating that the athlete will ultimately experience.

There's a cascade of effects that happens after all of these unfold. What can you say about that? Okay. Okay. I think beyond dehydration and dehydration cascade, which is like a reflection of an imbalance in the body homeostasis, what must be in the dust to this or the repercussion of it on organism. And it's important to know that it can kill. Okay. It's difficult to say, but it's very deadly. You're right. It's very deadly. Yeah. Yeah. Yeah. What environmental conditions are responsible for more deaths than all other sources of environmental mortality can be needed to name a fire or earthquakes.

This, it strokes mainly affect subject to tricks like elderly or people with chronic pathologies, but it can also affect athletes with exercise induced, it's stroke. It's stroke during the exercise is the second leading cause of death after cardiac arrest. And some authors even believe that the incidence of exercise induced, it's stroke is greatly underestimated and could be time times higher than that of cardiac arrest. So what happens when adaptive systems are overwhelmed?

If metabolic heat production exceeds dissipative capacity, body temperature gradually increase until exercise stops or heat-related illness. This pathological entity covers a wide spectrum of clinical forms ranging from hetedema or rash, muscle cramps, syncopa, to the most severe forms of heat exhaustion or exercise heat stroke. Exercise heat stroke is defined as a core body temperature above 40, 40.5 degrees associated with neurological disorder, loss of consciousness, confusion, irrational behavior, disorientation, etc.

related to physical exertion. This pathology is a medical emergency. When heat stress exceeds a certain threshold, the body will experience an exaggerated inflammatory response that may be associated with the development of disseminated intravascular coagulation, which is a critical pathophysiological feature of exercise induced its force. Indeed, the development of diffuse microtrombosis impairs blood flow in the microcirculation, leading to multi-organ dysfunction, brain, heart, lung, liver, and intestine, and even death.

Despite regular iteration during training, running, or exercise like at the walk, a post-exercise deficit in body water is observed, especially after prolonged exercise. This water deficit can have a deleterious effect on cardiovascular stress, exercise tolerance, performance, and health. In addition, as the rate of sweating increases during heat stress, there is a concomitant increase in electrolyte loss, particularly of sodium and chlorine. A potentially severe complication of endurance and ultraendurance event is exercise-associated hyponatremia.

A 2010 publication found hyponatremia in over half of participants in a neutral trait race in California. But this influence fluctuates widely in the literature. Several risk factors have been linked with the development of exercise-associated hyponatremia. The major risk factors seems to be over-hydration or excessive fluid consumption during activity. Whilst where hyper-hydration can lead to exercise-associated hyponatremia, hyponatremia during exercise in hot ambient condition can increase the risk of developing exorcional heat illness.

And moreover, pronounced dehydration associated with influence of muscle protein like neoglobin caused by muscle damage may lead to kidney damage and worsen the heat stress challenges. The prevalence of this acute kidney dysfunction in ultramarathon running is nearly 45% of all running according to literature. Okay, and I think that's it for the physiopathology and endopathology. So here's, I think, what the listeners can really take away from this. First off, in ultramarathon events, this aspect of dehydration is quite prevalent.

You said 45%, right? Yeah. When they're looking at, I think, the race in California that they're referring to as the Western States 100. Marty Hoffman, who's the former medical director there, has done a lot of research. Yeah, probably. Yeah, in that area. But there's this kind of one-two punch that dehydration has with respect to ultramarathoners. The first one is everybody realizes is that it decreases performance. Everybody knows that it seems to be a recognized aspect that we're trying to avoid dehydration. But the second thing is it actually decreases your thermal tolerance as well, which acts as a positive feedback loop because that, in turn, decreases exercise performance.

And also, as you mentioned, Nicholas, can have serious, much bigger than performance, serious health consequences. I mean, people can die from it. Not that we're trying to be alarmist or anything like that. But on the flip side of it, hyponatremia, which is low blood sodium, is primarily driven by overdrinking. And ultramarathoners have always been caught in this battle between staving off dehydration by consuming fluids and fluids with electrolytes and not consuming too much so that they end up hyponatremic. And it's not an easy problem for ultramarathoners to solve, as the literature indicates.

We see a lot of ultramarathoners at the end of races that are hyponatremic. And we see a lot of ultramarathoners at the end of races that are also dehydrated. And I'm kind of wondering, and Sebastian, you might need to jump into this. Why is this so difficult for runners to solve? Like, why is it so complex to just drink the right amount of fluid and have the right amount of electrolytes? It's kind of impossible to give an absolute amount for everybody. If you take two runners, one of them may sweat around 800 grams per hour, and another one may sweat more than 3 liters per hour. Yes. So there is huge inter-individual differences between runners, even between runners of the same level with the same training and so on.

So there is large inter-individual differences between different humans. So it's not possible to give an absolute number to drink per hour. So the take-home message that your audience should remember is, first, it's normal to lose some weight during an event. That's totally normal. You cannot expect to maintain your body weight during a race. Firstly, because capacity to drink is generally limited. So it's true that in ultramarathon with an hydration bag and so on, it's easier than in traditional marathon. But secondly, also, because your gut filtration capacity is quite limited, we cannot absorb more than 1.2 liter per hour.

So if you drink more than that, it's an average. It's different between people. But roughly, in average, we absorb a max of 1.2 liter per hour. So everything else that you drink will just stay in your stomach. It will not be of any benefit for you. You will just have a big, heavy stomach and nothing else. So first, second message is, it's normal to lose some weight during a race. Second message is, there is generally no point at drinking more than 1.2 liter per hour. And third message, drinking too much and gaining weight is absolutely not normal. Yes. If you're finishing a race with a higher body weight at your start the race, or even a training, that's a clear sign that you have been overdrinking. You can do the test during training.

Just jump on the scale when you're before to go for your run and when you come back. And if you have been gaining weight, it's clearly a sign that you have been drinking too much. All, Sebastian, all those messages have been resonated in this podcast several times. I'm kind of laughing over at the other end of this. Absolutely. Absolutely. There is a huge individual variability, not only in people's sweat rate, but also in people's sweat sodium concentrations. And it becomes very difficult and tricky to pinpoint. Some of the old time runners will remember, it wasn't that long ago that big races, at least here in the U.S., I know in Europe this has not been as common.

But here in the U.S., with big races such as the Western States 100 and the Wasatch 100, they used to weigh runners at certain aid stations. And if they were underweight by a certain percentage, and that percentage moved around over the years, they would either have to withdraw from the race or they would have to be held in the aid station until they got their weight up. We've now learned that that gives runners a poor message, Sebastian, as you were alluding to, where runners should be losing a little bit of weight, especially in an ultramarathon over the course of time. How much is debatable, and this is what the research is trying to tease out, but a few percent weight loss, it should be expected in an ultramarathon setting.

And we shouldn't try to be keeping people weight neutral in an ultramarathon setting. It is not only about how much, it is also about when to lose it. Because if you are getting dehydrated from the beginning of the race, then you will be dehydrated for the rest of the race. Because during the race itself, it will be impossible to reverse the dehydration due to limited absorption capacity. So the most important is to start the race well hydrated. So to drink well, for example, before the race also, not only during the race. But at the end of the race, it doesn't matter so much anymore. If you get dehydration during the last hour of the race, who cares? You're almost there. So your progressive dehydration will only have the last minute of your race.

So it's not the same effect. You should not be drinking with the same rate at the end of the race than you do at the beginning. And also, maybe I would like to say a word on that. It's not only the dehydration during the race. Hydration is a continuous process. That's a recovery after the race, with a drink, with a food, and that's also the preparation before the race. And sometimes we see people thinking, oh, I'm going to exercise in the heat, so I will drink a lot before. But when you do, the first response of your body when you drink more than usual is just to increase the urine production. You drink more, you pee more, to speak very simply. Because your body is not used to regulate that amount of water. And it takes two, three days to regulate it. So if you want to improve your hydration level before a race in hot and dead condition, you need to start drinking a bit more days before.

Not just before the race and during the race. Yes. Sebastian, those are great ways to sum things up. We're going to leave it at that. I really appreciate both of you guys' time. Nicholas, kind of starting with you, I'm going to put a link in the show notes to the research that you did. Because I think all athletes should go and take a look at it and read it. It's an easy read, even for people who aren't involved in reading scientific research. But where can people find more about some of the work that you're doing? We publish all the results of our work on Twitter. And we try to systematically popularize our articles in the form of deducted and understandable infographics. Of course, scientist articles are also available if you want.

I think you can find this in my Twitter account. It's at Nick N. Bouscarin. N-B-O-U-S-C-A-R-E-N. Sorry. And I'll include a link to that Twitter handle in the show notes as well. Sebastian, any final follow-ups from your end? Yeah. So in addition of Twitter, that is always an interesting source of information. I will also redirect you to the leaflet that was done by World Athletics regarding road race event. I appreciate that ultra endurance and road race event may be of a different world sometime. But still, there is some good and basic recommendation in this leaflet for amateur runners during mass participation event about how to manage a heat stress and to prepare for the heat stress.

And for the readers who are a bit more interested in the science behind it, a lot of educational material and resources have been published this year before the Tokyo Olympics. And the website of the British Journal of Sport Medicine includes a virtual e-edition with editorials with a simple take-home message and simple figures to illustrate how to prepare for the heat. Excellent. Well, thank both of you. I thank both of you on behalf of the community for the work that you're doing. Whenever I run across researchers that not only have an impact on performance, but also from a safety perspective, and obviously thermal stress is a big safety concern, as we mentioned from the onset.

I always think we need to give an extra special kudos and appreciate those researchers even more because there's more to life than performance and everybody wants to go out and push themselves. And if we can do it in a safe manner and be more educated about how things like heat actually impact us, I think it's all the better. So thank you guys. And thank you guys from the community. I really appreciate it. Nicholas, in particular for you, I know you're nervous about the English part of this. You did fantastic. Thank you. The listeners are going to love it. So I really appreciate you putting the time together to put some of these answers together for our listeners. Thank you, Dezen. And there you have it, folks. Much thanks to Nicholas and Sebastian for coming on the podcast today. Nicholas, I really appreciate you going out on a limb with this one.

I know that you're really nervous about English not being your first language, but I love the conversation. I hope that the listeners out there got a lot out of it. And I also appreciate the research that you have put into the space because this concept of heat stress is something that ultra runners are always going to have to contend with. And we always will have to learn more and more about it in order to maximize performance. Appreciate the heck out of everybody listening today. And as always, we will see you out on the trails. And we'll see you next time.