In this episode of the Athletes Compass podcast, hosts Paul Warloski and Dr. Paul Laursen, along with guest Marjaana Rakai, delve into the science and strategies behind heat acclimatization for endurance athletes. They discuss the physiological processes that occur when the body is exposed to heat, including increased heart rate and sweating, and the importance of evaporative cooling. The episode also covers genetic factors influencing heat tolerance, practical tips for acclimatizing to heat, and the benefits of active versus passive heat adaptation methods. Additionally, they explore the impact of fitness levels, nutritional strategies, and the critical balance between training stress and recovery.

Key Takeaways:

  • Evaporation is Key: Cooling occurs through the evaporation of sweat, not just sweating itself. Humidity hinders this process.
  • Genetic Factors: Some people have a genetic predisposition for better heat tolerance, influenced by heat shock proteins.
  • Active Acclimatization: Engaging in aerobic activities in the heat is more effective than passive methods like sitting in a sauna.
  • Training Adaptations: Aim for 5-14 days of heat exposure to see adaptations such as lower core temperature, increased sweat rate, and improved performance.
  • Hydration and Nutrition: Consume cold fluids and consider increasing carbohydrate intake during exercise in the heat due to higher glycolysis rates.
  • Avoid High Intensity in Heat: High-intensity workouts in heat can be overly stressful; focus on aerobic sessions in hot conditions.
  • Progressive Exposure: Gradually increase heat exposure time to adapt without overloading the body.
  • Mental Preparation: Mentally prepare for heat challenges and pace accordingly during races to manage core temperature.



Paul Warloski (00:27)

Hello and welcome to a new Athletes Compass podcast where we navigate training, fitness, and health for everyday athletes. In the Northern Hemisphere, we're getting closer, closer to summer and summer heat. That means acclimatizing our bodies to get used to the heat so we can still do our workouts and races despite. So we're talking

do we acclimatize to heat? What exactly is that? And how does it benefit endurance athletes? Paul, why don't you start us off?

Paul Laursen (00:57)

Sure, so heat acclimation or acclimatization is basically the process of getting hot and it basically that whole process after you adapt it helps so that you don't feel as you're getting as hot the next time and there's all these physiological processes that it helps.

And we probably, you know, I can see that's the second question. We probably need to go right there, right off the bat, Paul, is like, what

happens when you get exposure to heat and how do you heat out, heat acclimatize? So basically when you get hot, your heart rate increases, like your, well, your core temperature increases. And then the body thinks, well, we got to do something about that.

And it has two main means of working towards protecting its homeostasis. And the first one is that we all know is that we start to sweat more. And that's the process of creating sweat to our skin causes for the process of evaporation. So when we evaporate sweat from the skin, that cools the body.

And that's really important to recognize. Sweating itself doesn't cool you, but it's the process of evaporating that sweat is what cools you. And you know that when you go to someplace like Hawaii or some humid environment, and when you're in that humid environment, humidity means lots of waters in the air, and you're not able to evaporate that.

sweat from the skin, so therefore you can't cool your body as much. And that's why in humid environments you get you feel really hot. So that's the first process. The other one though is an increase in skin blood flow. So both of these require more cardiac output. So more volume of blood to the periphery of your body, the outside of your body. And that's got to be... and we see this when you start out, your heart rate

is through the roof, right, in the heat. You'll see a really high heart rate and that's because your cardiovascular system is struggling to deliver all of that water componentry to the outside, the periphery of the body, with the aim of getting rid of heat. Because one thing we should also mention, Paul, is that if we get too hot, we can die. It's a really dangerous sort of thing if you get too hot.

And the big one is that if you know when you're, if you've cooked a fried egg recently, you've cooked an egg on a fry pan, you'll see what happens to the proteins in that egg when it heats up, right? And that's called the process of denaturing. So they totally get reconfigured and change. So the same in effect would actually happen to you. You have this, we have this really, all of us, we have this really narrow temperature range.

that our bodies can only go outside. And actually we can go a lot cooler than we can hotter. So it's something like, you know, it's only like 41, 42 degrees and your proteins in your body are gonna start to denaturing and they come apart and they'll be non-functioning. So it's really can be, you know, quite damaging and indeed fatal, right? You can die at this. So this is a really important process that we evolved.

And in fact, that whole evolutionary step was so critical in our ability to thrive as humans. And in fact, it's something, the ability to evaporate sweat from the body was something that only, I believe only two or three or four other animals, I think it was the camel, the horse, and I blanked on the fourth one that can actually sweat to rid heat.

And they believe that this is, from an evolutionary standpoint, this enabled us to chase down prey in the desert when others were kind of scurrying for protective cover in the shade and enabled us to devour them and to take that fat that was required and to make our brains and to develop more connections and cognitive abilities.

So I'm all over the place here, Paul, but basically the main thing is that this vital adaptation of heat acclimation is super important, something we evolved relative to very few other animals. And the main thing we see is with repeated exposures of heat, we see a lower core temperature, an increased ability to sweat, an increased ability to deliver blood to the skin.

Paul Warloski (05:39)


Marjaana Rakai (05:41)

Thank you.

Paul Laursen (06:05)

and a lowered heart rate in terms of the main ones that we see, and of course an improved performance. So we also get a greater performance from this whole thing. So I'll stop there. And Marjaana did I miss anything?

Marjaana Rakai (06:20)

That was a lot, but I especially enjoyed the evolutionary tale there.

Paul Warloski (06:25)

Yeah, yeah.

Marjaana Rakai (06:26)

so I'm from the Arctic Circle.

The last 15 years I've tried to make myself love heat, but I still don't. Like I've lived in Rio de Janeiro, Dubai, like one of the most humid and hot environments in the world.

And I just freaking hate it. Like I would rather be skiing in the North Pole 365 days a year than, you know, run, bike, swim somewhere in the heat. And I wonder if there's genetic differences. I guess there's something, asking for a friend from the Arctic Circle here.

Paul Warloski (06:45)

I'm sorry.

Marjaana Rakai (07:11)

Is there something in our genetic, you know,

Paul Warloski (07:11)


Marjaana Rakai (07:17)

makeup that makes some people better heat adapted than others? And I have a good comparison though, because my Swedish friend Mia, hi Mia, we both lived in Dubai, we would work out together, we would run and bike. And one race particularly comes to mind, we met up for a warmup. I'm already

And I look at her and she's got nothing on her skin. She's all dry and I'm sweating. So obviously I like my heat tolerance or like my processes are working. I'm sweating. I'm trying to keep myself cool, right? And she's just standing there and like looking at me puzzle. Like, why are you sweating? And every time we went for a run, so bikes, like I would be sweating buckets and she was just like barely breaking a sweat. Like, and she's from...

Sweden. So our genetic base must be pretty close to similar. And even like based on our Garmin watches, our VOTs are quite similar. She kicks my ass on the run, but I kick her on the bike and swim. So we're pretty much at the same fitness level as well. So my question is, is there anything in genetic factors that could affect heat tolerance?

Paul Laursen (08:44)

Yeah, for sure. So I left that one out of the adaptation process and it's something so because I knew this was coming right. But it's yeah the other physiological adaptation that gets talked about less but it's pertinent relevant to what you're talking about is the adaptation of the heat shock protein and the heat shock protein sits within all of our cells and that is of course driven by you know your DNA.

So yes, Marjaana, it is something that is, does have a genetic component. And some of it, and what, you know, you asked, well, what's this heat shock protein thing all about? Well, heat shock protein is ultimately this regulator protein that sits to create tight junctions, ultimately tightness of your proteins. So remember we let off and we envisioned the egg that was frying, right? And then the proteins that were denaturing.

Well, you can imagine, I guess, ultimately that you had, you know, the MIA egg and the Marjaana egg. And the MIA egg, the MIA egg, when you crack it, it's slow to denature and stuff on the fry pan. The Marjaana egg, when you crack that one down, it's like, it's just like already at your fried egg kind of level, right? So it denatures super fast because the MIA egg, it has...

Paul Warloski (10:01)


Paul Laursen (10:10)

Like that genetic componentry is like, with the tight junctions and stuff, better heat shock proteins, better to withstand the heat resistance. And so, yeah, but the good news is, Marjaana, is that you can work towards the MEA egg by getting more and more exposures, right? So yeah, there is this plasticity of response. You can keep telling your proteins

you want them to develop the resistance to the heat. And that's what you get with those repeated exposures. But it takes a lot longer than the classic adaptations of reduced heart rate, of increased sweat rate, increased skin blood flow, increased performance. So there's kind of like a fast response and a slow response. And the heat shock protein one is like the chronic, slow response with a genetic component too. There's some that are like Mia, who are just better than others.

So I'm fortunate, I'm in the MIA camp, and this is really why I went down under to do my PhD. Like I wanted out of the Vancouver rain, and the cold Canadian climate. I was just so excited when I got my PhD scholarship down there because I just picked up the endless summer lifestyle with surfing and try, I love the heat.

And I'm Scandinavian like yourself, right, with Danish blood. So it's interesting there's that individual response, always an individual response with anything to do with training or stressors.

Marjaana Rakai (11:46)


I fry real quick.

Paul Warloski (11:51)


Paul Laursen (11:51)

You love the fried egg? I like that one.

Marjaana Rakai (11:54)

I like

I don't understand, I've tried to fry myself 15 years and I feel like I can passively tolerate heat a lot more, but when I start moving, it's still a struggle.

Paul Laursen (12:09)

don't forget, don't forget that like you're, you know, even though we sometimes live in these hot climates, like Rio or Dubai, it pushes a lot of us to go indoors in the air conditioning, right. And unfortunately, if you're going to do that, it, it sort of slows it all down, you're not sleeping in the heat. And really to get these kind of chronic exposures, you pretty much like I know a lot of

I remember a story from Simon Whitfield with, who's basically won, he won Sydney Gold in the triathlon and then he got silver in Beijing. And I remember, I think when the Canadian team booked accommodation for Simon, they went with in Beijing, they went without air conditioning because they wanted to kind of keep those adaptations going. And because they knew about that kind of chronic long exposure time to it where

the air conditioning can actually blunt what you're trying to get. This is at the elite level, of course, right? But it's a good story to remind us of the importance of that, the length of the stress exposure. So, yeah, it's a balance. It's a real balance. But that's an important piece of the puzzle to kind of think about when you're working towards your own event.

Paul Warloski (13:13)

Thanks for watching!

Marjaana Rakai (13:30)

For sure. My next event is this week, Saturday. And weather report is a little scary for me, plus 31 degrees as I come off the bike and during the first hour of my run. So I have been doing my workouts in the heat. Is there...

Like for others who are coming from cold climate, is it too late to start heat acclimatizing right now?

Paul Laursen (14:04)

No, never too late. Just, yeah, really like even like training too, right? Like it's never too late to get a little bit more training. You always, you don't wanna cook yourself, but yeah, there's, it's never too late. So yeah, you wanna give that stimulus, but what we have to realize with the heat stimulus is that it is a stress, it's a heat stress. So you're gonna give your body stress when you give it heat.

And that's part of the juggle of the, and that kind of goes into the whole cluster of training stress along with all the other different stressors. That's why you really have to be careful if you're ever doing anything high intensity in the heat. That can really be way too much stress. And that's probably the majority of the best, typically best practice is to do your aerobic sessions in the heat, not do HIIT sessions in the heat.

Save your HIIT sessions for the trainer and the cooler kind of climate to get the specific stimulus peripherally in the legs while you can kind of control the central stuff. Because if you're gonna go outside and do HIIT work in really hot conditions, you're giving yourself a double whammy. So you really have to be mindful of the added stress that you get with heat and work towards kind of balancing that.

Marjaana Rakai (15:27)

So you would stop, like if somebody is trying to do heat adaptation this week with the race Saturday, you would probably stop day before, two days before, for not doing your...

Paul Laursen (15:39)

Yeah, I mean, I just wouldn't do, it'd be like the taper, right? Like you want to gain freshness in that taper period. So, one or two days before you just, I wouldn't stay indoors all day, but it's like you wouldn't wanna go, maybe be outdoors the whole day. Like, you just give yourself a small heat window sort of stress. And again, the more acclimated that you are,

Paul Warloski (16:09)

Thank you.

Paul Laursen (16:09)

is a stressor to you. So yeah, it's just like training too, right? If you're at really high training loads, which I think we're gonna talk about next week, then you can probably handle a larger acute dose. So it's the same thing with the heat. If you're well heat acclimated, you can really handle these times outdoors. It's just like, it kind of doesn't phase you too much. You're like a Mia and your egg doesn't get fried.

Marjaana Rakai (16:43)

I love that.

Paul Warloski (16:43)

Just for clarification for our listeners, it's not just any old race that Marjaana is doing this week and it's Ironman Texas. I mean, she's doing an Ironman, which is no joke. And so it's a lot of intensity in the heat. It's not just spending a couple of minutes out there. So how long if Marjaana

for someone to get heat acclimatized and what factors influence this process?

Paul Laursen (17:17)

Yeah, so we already spoke about the genetic factor. Well, that one's always there, but who knows what everyone's at. And then also the recency of your exposure is gonna be also an influencer there. But if we look to the academic research papers, they typically show a period of anywhere from five to 14 days. Individually, you get a kick in your

you know, in all these various different responses. One of the big ones, actually, other important adaptations that I forgot to mention was the plasma volume response. So plasma volume is the water componentry of your cardiovascular system. And this is actually kidney driven. So your kidneys start retaining more salt, water follows salt into the blood compartment and your plasma volume expands.

So when your plasma volume expands, that lower, like increases your stroke volume, the volume of blood pumped each beat by the heart, and of course lowers the heart rate. So that's all kicked off by the, you know, we might've asked ourselves, well, why is heart rate lower? It's because, well, the kidney kind of kicked everything off. So that's really important to.

to realize ADH and aldosterone are the hormones that are involved that are creating that adaptation. But yeah, and this response, you are gonna get something certainly after probably three to five days in terms of that starting, the start process of the plasma volume expansion and the lowered heart rate. And then everything kind of just keeps going as you continue to give this stimulus, this heat stimulus over.

anywhere from five to 14 days and onwards. Now, this is a real passion topic for me, being in the high performance space that was with so many Olympic games in hot environments. This is something we really needed to research. I had a PhD student, Julia Casadio, who came in and did a whole PhD on

ways that you could go about from a high performance setting to heat acclimate. And she came up with these really cool models where you can actually like periodize the heat stimulus. In other words, you could come in just like a training plan where you do, you know, you periodize an endurance phase and just like the athletic plans, you know, you periodize a high intensity phase. The same sort of thing. You can come in and just do like three days of, three or four days of heat.

and then pull that out and then you could do some other things and then do another couple days of heat. So as long as you're continuing to give that heat stimulus, Julia showed in her research that you can maintain a good level of heat acclimation but still getting the other componentries of your training plan that you don't want to lose, right? For example, Marjaana has been training for Ironman. We've just been talking about that. She doesn't want to miss out.

on her long ride, irrespective of whether it's a hot or cold day, that's mint and super important for her success and performance in Ironman Texas. She needs that. So you wouldn't, even though maybe she's concerned about heat, you wouldn't just do a heat session on that day in light of the long session. So...

It's kind of cool because that means that we can use other methods like sauna or hot water immersion, like a spa or other means of getting that heat stimulus. So I'm all over the place again, Paul, as per usual. But basically, I'm kind of saying, I think the question was how long? Five to 14 days. And plasma volume expansion is a key adaptation physiological mechanism that we need to consider.

Marjaana Rakai (21:36)

So say somebody's aiming for hotter than their normal climate race, and they have two weeks to prepare themselves. So they could use sauna or make themselves something hot at home, like, you know, use a space heater or whatnot in a small room while they're biking. Do those like...

three days and then do long biograd the key sessions on a separate days that are not heat adaptation days. Would that work? Yeah.

Paul Laursen (22:17)

Absolutely, exactly. So as we always say, lots of ways to skin the cat, right, with our training and our training plans. But that's a great method. So you've got this repeated exposure. You've done three days of where you're in the heat of at least some duration. And yeah, we all have this context that we live around, whether if we're, say, in a cold environment or we're looking at the...

the travel plan and we can see that we're gonna be landing in Hawaii for, you know, six days in front. So we know we're gonna get, probably have the opportunity to get six days of heat acclimation, you know, when we land at the race, say for example. But maybe prior to that, coming from the cold climate, yeah, I've got a, you know, I've got a sauna available, I've got a hot tub available, and I'll do different means of actually being able to.

to get into that hot environment. The principle is, and this is really important, key point here, Paul, is that you have to get hot. Like very simply, you gotta get kind of uncomfortably hot a little bit. Just beyond uncomfortable in the heat for a given duration of time. How long is that duration? Well, how long is a piece of string, right? Like it's individual to your own tolerance. So, and like,

Marjaana versus Mia, right? Marjaana is probably not gonna be quite as tolerant as that of that time under heat as Mia is gonna be, right? But it's something that we definitely lengthen out. And I think of a classic Athletica example, and I believe this is Cindy wrote about this in her blog, but when Cindy did Kona and killed it there, she was doing, she was coming from September, late September, early October.

you know, late fall cool temperatures here in Revelstoke. And we, you know, we had to get into the sauna for that. And she was hating it. Kind of like you, she was like, oh! You know, she definitely had a Marjaana response. She was not enjoying her time in there. And she was starting like 15 minutes, kind of tolerant, but toleration time. But she progressed that out to, you know, 30, 35, 40 minutes by the end. And she was...

So again, you wanna just lengthen that exposure time within your own tolerance level. Don't be crazy, but you know, this is time being hot and uncomfortable is the stimulus that's going to adapt everything from the plasma volume response to the heart rate to the heat shock proteins eventually as well.

Marjaana Rakai (25:00)

So time for a fun fact.

There are 3.5 million saunas in Finland and a population of 5.5 million. I grew up in sauna basically. So you would think that because I, like, growing up, we had sauna almost every day we went to sauna. But I also enjoyed, you know, the tradition of jumping into a cold lake or...

Paul Warloski (25:08)

Ha ha

Marjaana Rakai (25:32)

making nude snow angels in between. You know, like you would go in sauna and then go out, cool off. That was my favorite part. It still is when we go to Finland, like just cool off as soon as possible. I can't stay there for too long, but I do enjoy sauna. I guess that's the only heat I enjoy.

Paul Laursen (25:54)

Yeah, well, I think that's what you should work towards. Maybe in the future, Marjaana, I love my sauna as well. That's been my greatest investment here in Revelstoke is that. But yeah, it's a great one to work on your own sort of tolerance. And there's so many benefits, right? From getting hot and getting too hot and getting too cold. But you know, I believe you want both

stress factors to be periodizing in your human physiology for your health.

Paul Warloski (26:36)

So my Garmin gives me a percentage of heat acclimatization based on, I'm not sure what it's based on, but how long I've been riding outside I assume. Is that an accurate number sort of?

Paul Laursen (26:54)

You got me, Paul. Honestly, I don't know what Garmin and the First Beat team are doing over there in that one. And it might be something that's good. I honestly haven't explored it. But yeah, that'll be something that, you know, us in Athletica, we do our own thing. And we'll be working on that one a little bit in the future for sure with the tools that we can leverage out there. But I don't know what Garmin

Paul Warloski (26:55)


Paul Laursen (27:22)

does for their heat acclamation.

Paul Warloski (27:26)

So we have five to 14 days that it takes to get heat acclimatized.

we need to increase our, this is kind of my three things in the middle here, but you know, we need to increase the bouts, but are there, is it enough to simply go ride or run in the heat doing our aerobic? Do we need to be in the sauna? Do we need to have other protocols that accelerate this process?

Paul Laursen (27:56)

Yeah, that's a really, really good point, Paul. And one that I probably didn't make very clear, but it's like if you had to pick a exercise mode like passive versus active that's going to be, is one gonna be more beneficial than the other one? It's certainly the active one. So active heat acclimation is more powerful than just passively sitting in the sauna.

or any other hot environments. So if you have an option, then definitely go for the moving one. And then, yeah, you want to, you know, again, I think it's anywhere from, if you're moving, anywhere from 30 minutes to 90 minutes is great. Of course, if you can go longer, like if, you know, I'm thinking when you arrive in Kona, if you've arrived 10 days before,

It's great if you can preview the course on a nice long slow ride, even like a modified version. And if you're going to do that, and I've done this many times, you're getting likely five to seven or eight hours out there kind of thing, just riding really slowly in those hot temperatures. So yeah, again, there's...

There's a bit of an art and science kind of thing here. We've been talking very a lot about the science, but at the end of the day, it's what, you know, it's the art that you can apply that science in the field when you get to your place like Marjaana's about to do here in Texas. So go Marjaana.

Paul Warloski (29:33)

Are there any risks that we need to be aware of in terms of

getting used to the heat?

Paul Laursen (29:38)

Yeah, for sure. And we did briefly touch on it, Paul, and it's just the fact that we have to recognize heat is a stress. And yeah, and it's just, and doing like HIIT training, there's, you know, there's a study, Chris Taylor, I think did it in the UK, and he, you know, he looked at doing HIIT in heat. And yeah, it's just a disaster, ultimately. It's like, cause it's just...

Paul Warloski (29:45)


Paul Laursen (30:05)

High intensity exercise, remember that when you're exercising, you're producing heat. And so imagine if you're producing heat, you're not able to rid it, and you're actually gaining more heat. Like your core temperature soars in high intensity work. So caution around high intensity work, and then caution with the progression of that as well. Like don't go big on day one, right? Day one of heat acclimation, and it's like, oh, I'm gonna have a monster heat session, right?

You really got to be in tune with your feel, monitor your heart rate, make sure that water and cold water is your friend on these sorts of sessions, so have that available. And again, as you become more accustomed to it, there is a way to augment the response, but it should only be used in well-conditioned athletes, and that is you can actually refrain

from drinking and you'll get a larger plasma volume response that's been established too. But this is only in the very experienced and already well heat acclimated individuals. Like if you're already up towards seven to 10 days kind of thing, you could abstain from drinking a little bit and then have a little bit more later. And then, yeah, in the post exercise period, that's when you need to replenish with both water and salts.

salts come in, you know, all meat, right? Remember all meat is like skeletal muscle, so it's going to be laden with all the salts that you want. So consider that as a post meal. You know, bacon is a classic one. Healthy, free range only if you can, but it's like, you know, salt and water. How are you going to get that back in you in the post exercise period?

so that you can rehydrate and that plasma volume is going to be repleted for the next time. That's the goal of the session. So give yourself the stimulus, but also give yourself all the tools to put back to make you more bulletproof for the next one.

Marjaana Rakai (32:14)

Is there differences in like a fitness level like VO2 max or gender? How well?

Paul Laursen (32:20)

Ah, yeah. Let's just start with fitness level. And this is, again, so glad you brought that up because that is another big co-founder. Fitness level itself is a way of heat acclimating. If your VO2 max is already high, if you're exercise training and trained, you already are partially heat acclimated. That's been shown in all the different studies. So that's, keep that in mind. Like fitness always rules. That's the number one sort of factor.

Paul Warloski (32:42)


Paul Laursen (32:49)

Gender, again, I always kind of think of the individual. I can, you know, potentially, I'm trying to think. Yeah, there may be some gender differences in terms of tolerance. Like, you know, females are typically, you know, rock stars and very tolerant to stress, but it's always the individual, right? So I'm only just reflecting on my...

Paul Warloski (33:04)

Thanks for watching!

Paul Laursen (33:18)

I'm reflecting on my own, the individuals and whatnot that I train. And, you know, I've had lots of Mias and stuff that just handle that heat quite well. And, and, but yeah, then there's, there's Marjaanas as well. So I really think it comes down more to an individual level. Um, you know, I maybe thinking about water components and men generally have more fat, uh, fat free mass fat free mass is going to have a larger water component to it than fat mass.

But again, I think these are really kind of come down to the individual as opposed to just blanketly saying, you know, females X, males Y. I think it just comes down to the individual. But fitness, no question. Fitter you are, the more heat acclimated you already are. But we still see an effect of this, right? So Alistair Brownlee...

Athletic ambassador, classic example. And he'll admit it as all itself. He saw him in the T100 in Miami and he was coming from the UK. He was leading that race, but the heat got to him in the end, right? Coming from that cold climate. And then, yeah. And we also look at the pros in those T100s in the Singapore race. This was a cooking hot race with that high humidity.

And you could see everyone just pouring everything on top of them in terms of the ice buckets and stuff. It was fantastic to watch. So, yes you will. Yes you will. Yeah.

Marjaana Rakai (34:47)

That's what I'm going to do. Ice, ice everywhere. And I was going to, because the lake temperature is probably going to be pretty hot. I'm dropping my, I'm going to do a swimsuit instead of tri-suit or wetsuit. I'm just going to go with the swimsuit and do full chains in the first, because I don't want to heat up during the first hour. So.

Paul Warloski (35:07)


Paul Laursen (35:10)

Yep, perfect. Yeah, and that is an interesting one too, right? So in warm temperatures, you don't get that evaporative sweet sweat loss that we let off the podcast with. So the only way you can rid heat is through conduction and convection of that water, the transfer of heat from your body to the water.

Paul Warloski (35:24)

Thanks for watching!

Paul Laursen (35:37)

but you don't get any sweat evaporation. Sweat evaporation is what cools. So that's why you won't get cool until, you know, you can, you build up all this heat in the swim sometimes in hot swims if you ever had those before. And then, yeah, you need to get rid of it when you, when you, you know, the cool air is passing through you on the bike and then you're able to sweat. And hopefully it's not, I don't know how humid it's going to be for the race, Marjaana have you looked at that?

Marjaana Rakai (36:05)

It could be pretty humid, like 60 to 80%. Typical. Yeah, typical Texas. But a lot of athletes, they want to wear wetsuits because the buoyancy effect, and they feel like they're faster on the swim. But I always think like if it's close to non-wetsuit legal, you should really be

Paul Laursen (36:12)

Oh yeah, that'll be a good test. Nice.

Paul Warloski (36:12)


Paul Laursen (36:17)


Marjaana Rakai (36:35)

Is it smart

cook underneath that wetsuit even if you're five

faster using the wetsuit than if you just swim with your dry suit or

swimsuit? Because at least if you're wearing a swimsuit, you're not cooking. You don't get the pre-cooling effect, which I would like to, like if it was nice and cool, 18 degrees Celsius.

for the rest of the day, but at least I won't be cooking.

Paul Warloski (37:02)

Thank you.

Paul Laursen (37:04)

Mm-hmm. Yeah. And another thing to keep in mind, Marjaana, as you go into, um, when you're preparing for the race and the in, make sure that, um, the, the drink that you're consuming is cold, ice cold, um, in that, you know, before you get in. So, and if you're feeling a little cold, a little chilly before you get in that water, don't like, don't worry about it too much. You don't want to be ice cold. You don't want to have cold.

cold muscles that are preventing you from going, but it's just a little cool and stuff. You want a cool core and warm muscles is the ideal sort of recipe for success, because that core is going to get a lot warmer later on during the day. Ice slushy is another great one you can use.

Paul Warloski (37:44)

Thanks for watching!

that actually brings me to my other question. Are there nutritional strategies? You know, ice cold food, but I mean, any supplements, anything that we can take before or during to help this process, or do we just need to keep cool?

Paul Laursen (38:03)

The only thing that's really important to note, Paul, in the heat, or the science says, is that you'll burn more carbs in hot conditions. So there's this... I don't know what happens. It's like... I don't know if it's... Basically, the data shows that you burn more sugar when the muscle is hot.

So, and why is that occurring? Well, not really sure, but glycolysis, for whatever reason, spins faster in hot conditions. And then, so if that's the case, it probably gives a bit of

Paul Warloski (38:33)


Paul Laursen (38:41)

a tip of the hat for, you know, consumptions of carbohydrates during exercise. But we're, you know, you're, that's going to be limited, you're going to be consuming, you know.

probably carbohydrates to the level of your tolerance during anyways. So, how much that's going to be, what we've spoken about this before, it can be anything from 50 to 120 grams an hour. But yeah, I guess just knowledge that glycolysis is sugar burning is happening a lot faster in the heat, well, then that's good to know. It's probably as important that I consume carbohydrates

during my race in the heat.

Yeah, and of course ice cold, ice cold fluids all the way. And anywhere you can put ice down your chest, under your armpits, in your hands or other great places, over your head, in your cap, whatever you can do, any place you can put ice. To get that added cooling effect, to keep the core temperature cool is...

is a bonus. Again, remember the number one factor is your brain is going to lower its exercise performance because it doesn't want you to turn into the fried egg, right? It doesn't want to denature that protein. It's going to do everything it can to protect you. So you're kind of in this whole battle throughout your race between your desire to go forward and your body's desire to protect itself.

This will be the tightrope that Marjaana walks as she goes through her Ironman Texas. And every other athlete that's out there that's listening to this, they're going through that same battle in their mind. And

that's, yeah, it's the fun part of endurance sport.

and this really comes down to the mind, being aware of that, right? Because the mental component is just so critical, right? Like you've got that, you know, Marjaanas you're getting ready to do this, right? Like you gotta almost rehearse in your mind going forward. There will be periods of heat in there. So mentally, you know, get used to that, condition the mind to accept that will be part and pace accordingly too, right?

If you're going out of the gates, remember every time when you're exercising, you're adding heat to the system. So, you know, because that's what happens when there's a, the metabolic byproduct is when we burn calories, fat and carbohydrates, it's an inefficient process. And, you know, 75% or thereabouts of the energy that's burnt goes as wasted heat.

And that creates our warm bloods. That's why we're sitting here as warm blooded animals right now in this podcast, which is fantastic. But unfortunately, when we're going in the exercise context, that's gonna really push our core temperature skyward. And when we increase the intensity, it's gonna move it even faster. So you've got to really pace and keep exercise intensity at bay and your mind knows what it needs to do.

to control all these sorts of factors. So trust it and yeah, and good luck.

Paul Warloski (42:05)

Yeah. The next podcast we do, not the next, but maybe in two podcasts, we'll see how the schedule turns out, but we're going to do some race reports of Marjaana's Texas Ironman and some of my gravel races. And we're going to get some response from Paul about how we did and some feedback and see if we can learn some things about our training program. So listen for that podcast.

adaptation, heat acclimatization. One is that it's not the sweat that's cooling your body so much, it's the evaporation that is cooling your body. And so therefore the humidity makes it harder to evaporate. And this is something that has got a biological component in terms of our historical roots chasing down animals. Number two,

do your aerobic work in the heat. It is better to be active than passive. I mean, saunas are great. There's a lot of different ways to skin a cat in Paul's terms, but doing the active work is usually better and more efficient than passive work, but you might consider doing the intensity work inside because that is a double whammy in the heat. And finally,

you need to get uncomfortably hot. You need to continue to lengthen your exposure to get heat adapted. Heat stimulus is, that's how you adapt to everything. It takes five to 14 days to get fully adapted and it just takes time in the heat. So get out and ride your bike and run. That is all for this week. Thank you for listening and join us next week for the Athletes Compass podcast. You can help us by asking your training questions in the comments.

liking and sharing the podcast and giving us five star reviews and engaging with us on our social media. From Marjaana Rakai and Dr. Paul Laursen I am Paul Warloski and this has been the Athletes Compass Podcast.

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