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Antoine Jolicoeur-Desroches on Heat, Omius, and CORE
870 Plays1 month ago
Former pro triathlete and PhD candidate Antoine Jolicoeur-Desroches speaks with Andrew and Michael about training and racing in hot conditions and his two studies on popular devices: the Omius headband paper and the CORE Body Temperature sensor paper. We cover:
- advantages and limitations of the Omius headband and potential use cases
- combining pre-cooling and per-cooling strategies
- combining internal and external cooling strategies
- advantages and limitations of the CORE body temperature sensor and use cases
- influence of motivation on response to increased core temperature during exercise, especially in elite athletes.
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Transcript
Finding OMSN Band Content
00:00:00
Speaker
I just wanted to to see if there was any, if there were any information on the OMSN band, like if there was any ah podcast interviews. And I think it's the only one that that I've seen. And I actually didn't know it was ah your podcast. So that's quite funny.
Podcast Introduction
00:00:22
Speaker
Hi, everyone. I'm Andrew. And I'm Michael. And you're listening to the Endurance Innovation Podcast.
Introduction of Antoine Jellicher de Roche
00:00:39
Speaker
Hey everyone and welcome back to Endurance Innovation Podcast. Continuing ah with our theme of cooling, joining us today is a almost former pro triathlete, an ultra distance runner, um a PhD student at the University of Sherbrooke in Quebec in Canada here.
00:01:00
Speaker
ah studying thermal regulation and cooling strategies in endurance sports.
Research on Cooling Strategies
00:01:05
Speaker
I'm very pleased to welcome Antoine Jellicher de Roche to our show. Antoine, welcome. Thank you very much for taking the time. ah Yes, ah thanks for having me. Yeah. And it only ah listeners it only took me two takes to get Antoine's name mostly correct. Yeah, that's pretty good. yeah it's listen It's always tough for Anglophones.
00:01:24
Speaker
Yeah, yeah. So Antoine, as I said in the intro, where' we're really... having ah having a deep focus into into cooling in these last, well, in the last episode we published in the next couple that we will we will as an anticipation of a product launch that is relevant to cooling. And you were kind of on my radar as ah as a Canadian pro, as ah most Canadian pro triathletes would have been. ah But recently, your your name came up in ah an article that I read on the the sweat signs column that Alex Hutchinson's write.
00:01:55
Speaker
Alex Hutchinson writes for Outside Magazine. Really struggling with names today. um And there was a paper of yours that he cited where you looked at the the the efficacy of the Omias headband, who we've talked to the founders on past shows, or a past show. And this is ah this isnt definitely an interesting topic of debate. So I want to start there. So maybe if you'd like um take us through the findings of that paper, and then we can dive right in and pepper you with some questions.
00:02:25
Speaker
Or maybe even a little bit of background to to start, just so people know exactly where you're coming from. ah Yeah, so, well, I've known about, like, basically, I think the the first time that Omias had been, like, came into the world of triathlon, because ah recently we've seen, ah like, Kipchoge and Asan ah use it at the Paris Olympics, which was pretty cool for me, because my article, which was just published so it increased the visibility of the the article quite a lot to see ah Kipto here use it. But firstly, as a ah a lot of things, I feel like two athletes like to to test stuff and like to geek out that stuff. So and john ah so the cooling event really entered this
00:03:16
Speaker
the the sports in Trotland and it was at the 2019 Kona, so the Ironman World Championship. so ah And the the cooling at Ben is ah It's basically 20 cubes of made out of graphics and each one has nine little ah sort of towers which is made to sort of increase increase the surface area of your forehead and the goal of it is to to cool your head.
00:03:51
Speaker
and basically to to reduce your percentage of eat and hopefully ah improve your performance. So that's why, yeah that's what we wanted to to test out. And ah it was the first study to just test test it out. And for us, was we we actually wanted to publish it before the Paris Sonic game, because we knew that some athletes were going to use it. ah Because ah as as we know, like, ah with the climate change and ah everything there's a lot of more heat waves and the temperature is always increasing and there's also a lot more events happening like in Qatar and Dubai and really warm places and it's only always going to increase the the issue of ah performing in the heat so that's why for us I think there's
00:04:40
Speaker
yeah It's already a big field of study to study a cooling strategy, ah but it's just going to continue to to be become better because it's going to be
Impact of Climate Change on Sports
00:04:51
Speaker
a big issue. And when you're competing in the eat, ah that's the main factor that's going to impact your your performance, ah no matter how fit you are.
00:05:00
Speaker
If your core body temperature goes close to 40 degrees Celsius, it's going to be really hard to be able to push your body. ah So that's why there was there's ways our body tries to dissipate ah your body by sweating, ah by ah cooling your body by the blood is going to go to the to your skin to try to dissipate the heat. But sometimes that that's not enough. and That's why a lot of people use pre-cooling. So to cool your body before the exercise, poor cooling to cool their body during exercise and also post-cooling well to to try to cool yourself after after the race. But personally what I study more in my my thesis and my PhD, it's more ah
00:05:44
Speaker
pre and power cooling strategy, so things that can actually help you to to improve your performance. The Omius is a power cooling strategy, so cooling during the exercise, so to try to to cool yourself while while you while you exercise or
Innovative Cooling Methods
00:06:00
Speaker
compete.
00:06:00
Speaker
And per cooling presents a really interesting challenge because you know you it can't get in the way of the of the exercise or the competition. right In pre-cooling, you have all sorts of all sorts of strategies that you can employ that that are not feasible in in per cooling. And that's why that's why we don't see that many you know as many solutions, as ah as obviously, as there are pre-cooling solutions. And we've covered them quite a bit, Andrew and I, and with with other folks. so But this is this is a really interesting one.
00:06:29
Speaker
Yeah, and I mean, there's a lot to unpack there. You're you're really easy to interview because you do all the yeah the technical stuff without without any problem. But yeah, you you brought up a lot of good points. So first of all, the Omias headband has been everywhere. um If you watch any kind of hot race coverage, whether it's triathlon or like you said, the Paris Olympics, you will see people wearing it. And for me, it's especially interesting that Kona was one of the places where it debuted.
00:06:58
Speaker
um And that's because it's such a humid environment. So the ah purpose behind it or the the science behind it is it's trying to increase the rate of evaporation of sweat by increasing the surface area. And there's no question that that part of the science works. um Just whether it has a notable impact on your core body temperature or ultimately on your speed is the is the real question that you set out to answer.
00:07:21
Speaker
um So, I think there's i mean there's a a huge amount to discuss there. That's a great point that you that you said. It's like when you try to cool yourself, the the bigger the surface area, the better it's going to be to to cool yourself. That's why the like the best post-coaling strategy is to to go in ah ice water or really cold water because all your body is being cool. And one of the best pre-cooling strategy is to use an ice vest because the torso is such a big ah big area to to cool yourself. But like you can't you can't stop doing an environment to to jump in the in the water. like Some people do it in ultra marathon like ah because it takes so much time. It's not a big issue to to waste two, three minutes to to cool yourself. But when you're doing a marathon, you you need to be ah
00:08:14
Speaker
you can't lose time and also the the weight of a vest, it's maybe like two to three kilos. yeah that's That's too much and that's gonna affect your running economy and your your performance. So you need something that you can actually wear, something that's not too heavy.
00:08:30
Speaker
ah And, uh, that's not going to affect how you, you perform. Uh, that's why the the idea of the home use is quite interesting because the, the ed is an area that's available. Like while, while you run, there's, there's nothing that's like you've maybe have a headband or a hat, but you can still put the.
00:08:50
Speaker
Yeah, you're wearing something on there anyway, most of the time. Exactly. And it doesn't wait a lot, so it doesn't affect your running economy. And the end is actually a really interesting place to call yourself, because ah There's a different factor but basically ah your your brain and more specifically the hypothalamus is basically like your thermostat of your body and it tells you if you need to to warm yourself or to cool yourself and in our body there's quite a lot of like thermo receptors we're going to notice if you're eating up.
00:09:30
Speaker
Basically, if you're eating up ah your core bodies increasing or your skin temperature is increasing, it tells that to to your to your brain. And during exercise, here your your brain ah actually increased temperature and that's a big issue to ah that can cause a stroke or basically there's also like the the central government theory that basically your brain is telling you to to slow down before you actually go go into a stroke. So basically by cooling your brain that could actually be ah quite useful to maybe help you to to push yourself more or basically if you can actually
00:10:12
Speaker
ah tell your body that you're actually cooler, even though your core body temperature hasn't changed, that can help you to actually go
Cooling the Brain: Benefits and Risks
00:10:21
Speaker
faster. ah Maybe you're actually going to finish ah the exercise at the higher core body temperature, which can maybe be dangerous. And that's one of the, ah that's similar to mental, which is like what we use in, ah in gums, that some people drink mental,
00:10:41
Speaker
A lot of people have used it during the Tokyo Olympic Games. ah So that has like no effect at all on your core body temperature. But it has a refreshing ah feeling, like you you see when you brush your teeth. It's refreshing. And everyone smells really good, too. yeah So you're running, you're suffering, but you smell good. And that actually can help to to feel a little bit cooler. So that tells your brain, oh it's even though it's like 35 degrees outside, it's not that bad. So you're you're basically tricking your your your mind, your body to to push harder so that you can maybe ah run faster ah and improve ah performance. ah So that's why like cooling the end, it's actually ah
00:11:31
Speaker
Either the forehead or directly ah the head is a nice place to to cool yourself. and there is no ah like The adipose level is really low on the head, so if you put ice or cold water, ah well, there's no ah insulation from the adipose tissue. ah the vazo There's not much vasoconstriction happening in the head contrary to the the arms or or the ends.
00:11:58
Speaker
ah which I see a lot of athletes putting ice in our indoor ads in their end, which might be useful, but there's a lot of vasoconstriction on the end. But in a hot environment, would you see vasoconstriction in the extremities? Because it's it's hot and you're probably going to be pretty dilated even even in the extremities. I totally hear what you're saying. In cool conditions, yes, you would have vasoconstriction in your hands and your feet, but when it's hot... It depends if it's really, really cold. ah like super cold ice, there's still going to be some vaso countries. Actually, it's still a beneficial. ah But that's why ah you've probably heard about the it's a Stanford researcher who've developed the end cooling device, which is actually really cool. It's ah basically there's some cold
00:12:48
Speaker
You put your end inside a box. There's some cold air, but there's also some suction that's happening, which helps to refine your vasoconstriction. So your end is still vasodated. So there is a cooling happening, but it's it's almost like ah a suction happening at at the same time. and that's supposed to cool yourself quite a lot. And ah some people have i've used it in like, ah I think in full football match, they've used it. In other research they've used it, but I've seen some like research trying to do it on the like running, but you do it on a treadmill and you have to put your end at the stationary, which is not a little bit invasive at that point. Yeah. yeah
00:13:37
Speaker
And that's that's a perfect example of why the per cooling methods are so difficult. Yeah. Because you you can come up with these really clever things that kind of bypass the body's own mechanisms, but you have to be able to take it with you. You have to be able to. Exactly. Yeah. That's why it's a well and an issue a little bit in the sports hands. Like there's quite a lot of ah research on ice vests and we know it works well.
00:14:04
Speaker
But if nobody's going to ride, like there's a lot of like site in stationary cycling with an ice vest, but nobody's going to ride their bike with, uh, with an ISIS.
Pre-Cooling and Per-Cooling Strategies
00:14:14
Speaker
So that's not like the external value of the study is not really interesting because it's not, uh, it's not something you can actually use, uh, in the actual world in a competition. you know Yeah.
00:14:26
Speaker
You can pre-cool with it quite effectively, and I think pre-cooling is an effective strategy for shorter events. Yeah, pre-cooling with the iZvS is really good, but not the pre-cooling, and that's why the best strategy is to use a combination of pre-cooling and pre-cooling, because usually pre-cooling is going to last about 20 to 25 minutes, maybe 30 minutes, but it's quite short. So if you do a pre-cooling strategy before a marathon,
00:14:52
Speaker
you You also need to do a percoding strategy if no it's not really going to matter. and especially it's not The first 20-25 minutes are not the most important part of the ah marathon.
00:15:03
Speaker
ah and actually As I explained, there are different types of like cooling strategies, depending on the moment. But there are also different types of cooling strategies, depending on the strategy of the cooling. So there is external cooling, which is like ah the omias. It's external because you put it on your end.
00:15:22
Speaker
and water immersion is external but there's also internal cooling which is ah drinking cold water or drinking sludge so if you during exercise if you can combine both ah that's the best too so you you cool yourself from the inside and but also from the the inside ah the outside and that's the the best way to actually cool yourself the the most efficiently And we had actually spoken to Paul Larson, who had come up with a bottle. ah I don't know if you've seen this, Antoine, but it's a bottle that allows you to drink slush more effectively. um So it's basically a way of supercharging brain freeze, which it's it very effective. If you can pallet the extra slush, it will cool your body very effectively. and And that's one of your studies as well, I think.
00:16:12
Speaker
looking at the effects of cold water on on performance.
Methodology of Omius Headband Study
00:16:16
Speaker
but um yeah I feel like we've there's so much to cover here. yeah where we i think we need to I think we need to zoom back into the and into the actual study. yeah so yeah Maybe I can talk about the my ah protocol for the OMIU study and what we what we found. Yes, please. ah so Basically, the instead of doing and We wanted to replicate a long effort, so that's ah beneficial to actually actual ah condition like in marathon, half marathon, or a triathlon. But what I find really interesting is is to do a combination of a submaximal effort and a time trial. Because basically, especially for a device like that, because
00:16:59
Speaker
Uh, we want to see if, uh, so what, what they did is they did 70, 70 minutes at 60% of door view to max and then, uh, five kilometer time trial. So for most people, and this is running, of course. Yeah.
00:17:15
Speaker
and Running, yeah. And for most people, that's about like one hour and a half, 90 minutes total effort. And that's at 35 degrees Celsius and 65% humidity. So hang on, were they stacked? So they were 70 minutes submaximal followed immediately by the time trial?
00:17:30
Speaker
ah Yes, yeah immediately. they did There were some 45 seconds ah stops at every ah five or 10 minutes, ah just to because we were actually also measuring overall the temperature. And ah and ussh we had to stop the participant participant to spread our head on the door for Ed to make sure that the the cooling had been was always ah wet. Okay.
00:17:58
Speaker
ah so So, the participant came, they did the VO2 max test, all the testing, then they did the familiarization, and then there were two conditions. And because we knew that there might be a big possible effect with the OMSet band, we actually developed a 3D printed ad band, which I think was pretty cool. It was pretty cool, yeah. I saw photos of this thing.
00:18:25
Speaker
I like the description of this, especially the name of the sham head. I could work with ah with a guy who did it, and I was super impressed by it, because that was, ah so the it did, it 3D printed it, and then it it was like, ah oh, I've got a nice spray that can put it on it, and it's going to look like exactly like it. And even for me, who were manipulat manipulating the bolt, sometimes I really had to like touch touch them to make sure which one was them. So I think it was good that people couldn't see a which headband was what, because that was really important to take out the placebo effect. And on top of that, you put it in the fridge as well, just to... ah Yeah, for the cham headband, we have put it in the fridge to make sure that as soon as they put it, it would feel ah feel cool.
00:19:15
Speaker
So I wanted to see so all the measurement that we took. for for ah at At first, we determined if the they arrive at the laboratory ah in the same hydration state. So we measured or analyzed their blood and we all analyzed their urine. And during that third test, ah we measured our carbon body temperature. ah So we measure it rectally. Then ah skin temperature at different places ah on our body. Also forehead temperature with ah infrared thermometer. ah And then oral canal temperature as well. ah And we also measure perceived exertion ah overall temperature. overall thermal comfort and also forehead thermal comfort. ah And so we measured that throughout the test. And what we've seen ah
00:20:17
Speaker
And our our hypothesis was that it would help to to improve perceived exertion, thermal comfort, and per ah forehead thermal comfort so that people could ah run faster during the the five kilometer time trial.
Omius Headband Findings and Applications
00:20:34
Speaker
But we didn't expect to have any effect on the core body temperature.
00:20:40
Speaker
ah but what did actually happen is ah it only reduced the forehead temperature during the submaximal running but not during the 5K and it reduced the perception of forehead temperature only during the submaximal but not during the 5K temperature but it had no impact on like core body temperature ah Even for a temperature after the 5K and thermal comfort and for a temperature during the 5K, it had no impact, but it still had some impact on the perceived exortion ah perceived yeah temperature of the forehead. So there's still some cooling effect with the Omi-Sal-Ben.
00:21:28
Speaker
but it has no impact on actual thermal regulation, and it had no impact on the time trial performance, so they didn't run faster with the OMIUS event.
00:21:40
Speaker
So that's really interesting that it it did affect the submaximal effort, but not the, not the time trial. So do you think there's a, there could be a use for this where for a longer race, a lower intensity race, like ultra running, um, where that may be a useful intervention? Yeah. And that's, um, not sure if I talk about it like in the discussion or maybe it was when I was talking, uh, to Alex attention, uh, when he was writing this, uh,
00:22:08
Speaker
this ah article. I think that a 5K time trial is quite a hard ah effort. And as we've seen, like this device is mostly used in Ironman racing or in marathon, ah where the intensity is is quite a lot lower than and a 5K race.
00:22:27
Speaker
ah So my hypothesis why it reduced the forehead temperature and the perceived temperature on the forehead only during the submaximal is that maybe during the 5K, the heat is way too way too high and the the effort is way too high for...
00:22:49
Speaker
like the cooling effect is not that strong to have an impact on when the the effort is almost maximal like a 5k it's really hard but ah maybe on a marathon ah if it can reduce slightly or perceive ah temperature on the forehead ah maybe slightly or overall cooling or overall temporal comfort ah maybe it can actually help to yourself to to push ah to push harder. But like that's why it was interesting for us to to do both ah the submaximal and the 5K. So we could see that at 60% of our V2 max. So
00:23:31
Speaker
It's quite a hard running, especially when you're running at 35 degrees, but it's not like a maximal effort effort. And it's lower than a marathon pace. ah Well, it had no impact on the dark core body temperature. ah But what was so surprising, it didn't have any impact on perceived exertion, even during the submaximal effort, which as I hypothesize that it would have an impact because most most cooling strategies have an impact on perceived exertion at a lower intensity and maybe not at a 5K time trial intensity.
00:24:12
Speaker
That is an interesting finding. And that's kind of what we were we were trying to tease apart with our question to you is, ah is um you know can there be a benefit um just from the just from the perceived exertion ah or the perceived thermal comfort versus ah an actual ah reduction in in core body temperature?
Athletes' Heat Tolerance
00:24:31
Speaker
Yeah, I think that well, at athletes can actually tolerate all your core body temperature than regular people. And that's why some time, well, I don't know if you've seen the the core body device ah article on the blue man felt at the the that not this year Kona but the previous one, ah like for at least 30 minutes it was running at over 40 degrees core body temperature which is quite quite insane. yeah So athletes can actually push themselves to so much higher levels of
00:25:11
Speaker
Well, pain and actual critical, like for, for most people, 40 degrees, uh, is a critical level and they would probably not be able to to run, but I don't be running at that that speed. yeah and So people can actually at least can actually push themselves ah higher. And if a device that doesn't have any impact on core body temperature, but tells yourself that you can push yourself even more, it can have, uh, maybe a slight impact and.
00:25:42
Speaker
As in any sport, we're always looking for like marginal gain. sure ah So maybe it can help. That's why even though mental doesn't have any impact on the coverage body temperature, a lot of athletes ah still use it.
00:25:56
Speaker
ah But for sure, personally, I would prefer to like use a hat that I just put on with lots of ice, cold water, and I put it on my my head. ah And that's what Manus de Clef used at the corner. I was about to mention that. Personally, um I was really happy when I saw like he executed like a really good race, but as especially a really good cooling strategy during his marathon. He was taking his time during the the A station to really
00:26:30
Speaker
put ice in in in his body, in his try suit, ice in his head, ah especially like the the the the hat that he made or something like that. the super nices I was going to say, yeah, maybe maybe the best innovation is just a a roomy hat.
00:26:46
Speaker
Yeah, it's actually like it's new in the Toronto world, but like in ultra marathon, like other some people use it like in the Winston state when it's really, really ah warm. And I don't think it could be useful like in ah actual marathon, because they're running so fast that I think that much ice moving around in your on your head is not useful when you're running at over 20k per hour. But like for amateurs or for like during an hour man or doing an ultra marathon, I think that can be Yeah, useful to to cool yourself like that. the The other thing I think I saw of Magnus doing was taking a stocking. and So a woman stocking, filling it with ice and putting it down his back. ah I've done that for cycling before. I've never done that for running. um But that's really neat because the ice melts and it just all this cool water drips down your body. So you get all the the phase change. You get the the cool water on you through a big surface area and then the evaporation. And then it's small thing to carry with you. and that's and yeah That's why like the the type of race you do, it's important like to consider like what coding strategy you can actually use. because
00:27:55
Speaker
ah Like in in a marathon, you can't really maybe slow down to put ice in a stocking. But in an Ironman, you have more time than that's become. And the issue of it is a bigger factor than the issue of losing 20 seconds to to slow down. you know So it's always about like trying to find what's the better option in the specific circumstances.
00:28:21
Speaker
So there's one other point I wanted to bring up, and I'm sure you're aware of this study, but I think it was in 2016 in Doha, Qatar, where the the UCI i World Championships were held, and they actually had a bunch of the time trialists instrumented, and they took the core body temperature measurements. And they found exactly what you were saying before, that trained athletes can go above and stay above 40 degrees Celsius for quite ah quite a long amount of time, much higher than anyone it had expected before that study.
00:28:49
Speaker
Yeah, I've seen that that study and sometimes in my in tradition of articles or even my thesis, I i plug ah plug that and that's quite interesting and especially like there's some study also just measure measure the core temperature, the temperature of athletes at the end of a marathon. it's Quite a lot of time it's over 40 degrees. And sometimes what's pretty crazy is that ah the temperature outside is not that warm, but people still ah reach really high carbony temperature. So yes, like external factors like solar radiation, the temperature outside is a big factor, but the biggest factor factor is actually your temperature. your metabolic heat, and that's why sometimes, the especially amongst amateurs, the biggest issue of heat stroke is not during the marathon, but it's during shorter races when people actually push themselves ah much higher and produce a lot of heat. It's a good perspective to look at, and it's something that we've been saying for a number of years, but just the heat is one of the major limiting factors for performance. yeahp And I think people are starting to realize that. And like we said in the introduction, the world is getting hotter, races are getting hotter, the weather is getting more extreme. So we're going to see this more and more often. And it's, I think it is the path to faster performances is better thermal management of athletes. And it's actually quite well it's quite simple. It's not like the the amount of like of money and time and investment that you to improve like your your bicycle position. is like you You see like people putting like thousands and thousands of dollars to and to maybe gain two, three watts. But the amount of, like if you see Kona,
00:30:37
Speaker
except maybe Patrick Lang, like the running times are not that fast. And that shows you how much the ETH has an impact on on running performance. And that's ah pretty that's why if you can in if you can improve your coding strategy, or if to do like, well,
00:30:59
Speaker
a good acclimatization, like the, the Norwegian do really well and improve your performance in the eat that can have and a big factor. And that's, that's why like, uh, Blumenfeld did so well at the Tokyo Olympic games, which was quite surprising for like, uh, no Norwegian to, to win at the warmest Norwegian to like, he's not a small human. So his surface area, the volume ratio is pretty low compared to some of his compatriots.
00:31:24
Speaker
Yeah. And I've heard something about their like acclimatization protocol and I've like, it's, it seems like quite, quite intense, but that's all the saunas all the time. Right. Yeah. Yeah. Yeah. That's what's required to, to perform at the ISO like that. Yeah. And now it was really cool. It's, we see people using it acclimatization, but for not to, to race in warm environment, but just to improve their like plasma volume and just to become better, uh,
00:31:50
Speaker
in any races, whether it's cold. It's the new, are it's the new altitude training. Apparently. Yeah. Easier to do. I remember hearing stories about so some of the National Cycling Federation's where when they were traveling to an event, they would basically lock themselves in the bathroom, turn on the shower. This is in the hotel, turn on the shower, get it really steamy, and they'd have their bike set up on a trainer or something. And they would exercise under this really, really hot condition to help with the blood plasma volume. um So it's it's a neat adaptation ah or a neat strategy that people have developed in in response to that. So it's definitely a performance improvement. Yeah, for sure. yeah and doesn't take like As you said, it doesn't take that much. like and Especially just just cycling without a fan, you your core body temperature is going to reach 39 degrees like pretty easily at the end of your session. yeah
00:32:40
Speaker
Yeah, yeah. So I'm going to move us on, if that's okay with
Core Temperature Sensors: Study and Use
00:32:44
Speaker
you guys. um just I think we we did a ah real good job of covering the your findings on the Omius headband. um There's another piece that you wrote ah that I'm very interested to learn more about, and that is ah uh, your study on the core body temperature sensor, um, which is, uh, as we mentioned in the intro, uh, something that I've used a fair bit and Andrews used in the past. We've had them on the show, I think at least once, if not twice, it's been a little while, but, uh, you see them, you see the little, little white rectangle, white square underneath jerseys all over the, all over the place. That's just like the old me his head band. You, if you know where to look, the OMIUS headband is probably a little bit more obvious, but the course answer, if you, if you look at the, at the, at the kits of the, uh, the pro cycling teams and the pro triathletes, it's usually in there, uh, on the, the left side of the chest. Well, especially when they're on the bike, when you, you have the moto's video recording, everything, it's just put right out in front of them. So it's very visible. Um, so yeah, I'm very curious to hear what you found and, uh, what you, why don't we start with, uh, with kind of what, what it purports to do and what you were trying to learn about, uh, about it.
00:33:56
Speaker
Yeah, actually, yeah, I learned about the the core, like when we just came out and I was doing my my master and actually wrote to to the guys at Core just, or could you send me a device just to try it as more like as an athlete and stuff like that. And when I did my ah my PhD, I was curious to try to test it. And we actually tested it at the same time as we did my hyperhydration study, which was basically the protocol was a two-hour hydration protocol, and then at five kilometer time trial at 30 degrees Celsius and 50% humidity.
00:34:43
Speaker
But the validity of the core we tested it during the control part of the the study. Oh, okay. Interesting. ah We actually have our also results of the when they actually did the operation that maybe we'll publish another article to validate when the people actually consume a lot of of fluids. But but for this this study, ah basically,
00:35:07
Speaker
ah So the hydration period was ah two hours, but for the the control, ah people drank ah some ah some fluid based on their body weight under the first five minutes, and the the water was at four degrees Celsius, so quite ah quite cold. ah so how How much water are we talking about? like So you said it there was pegged to body weight?
00:35:36
Speaker
Yeah, so I can actually tell you a bit around here. So it's a 7.5 milliliter per kilogram. So if you're like, I can actually do the calculation right now. It's like, if you're 70.
00:35:50
Speaker
70, that's about a little bit more than 500 millimeter of water. But when they did the actual like hyper-hydration study, that they were the in average, day they drank more than 700 meter of water, just quite a lot.
00:36:10
Speaker
and So what was interesting is that we had, and to compare, ah people ah ingested a gastrointestinal pill ah the night before, so at least either 10 or 12 hours before the the beginning of the experimentation.
00:36:29
Speaker
to make sure that the pill was actually low enough so that the measurements were not affected by the liquids. The pill is a little just gastrointestinal thermometer, right? Like it's a little... Yes, exactly. Like it's a core COR. Yeah. And I think it's the same that you use in your study as well.
00:36:50
Speaker
Oh, yes. Yeah, it was probably very similar to that. Much easier to swallow than the actual core body temperature sensor. Do not recommend that. Yeah. And that's that's why I think like that's a good point. that That's why I think that ah I think companies that develop things like the core car sensor, it's really important because anyone who have like ingested a core pill which costs $80 or $80 to $90, it's quite expensive. It's really hard to get. ah So it's not accessible to to athletes.
00:37:20
Speaker
especially now it's a lot harder to to get. ah the The other strategy is what we use in our other studies to to take the the pill, which is the gastrointestinal pill, but we put it in ah in a preservative, like ah a con condom. yep So then they use it rectally so that we can use it a few more times, but it's quite an invasive ah technique. So that's why different Different barrier to entry, but probably still a little bit of an issue. exactly Yeah, exactly. You need to be really motivated to know the temperature to do that. ah like for ah For science, like for research, it's it's useful. but like
00:38:03
Speaker
you won't be able to to ask a lot of athletes to do it, especially when you're a lot of people. That's why the the core sensor that you can, it's not that expensive. You can use a lot of times, like as many times as you want. That's quite quite useful, but it needs to be precise. It needs to be valid. And that's what we wanted to to measure. ah So we compared the the core temperature with the gas intestinal during a sitting period, but also during the 5K time trial.
00:38:30
Speaker
okay and the When they did the 5K and it's the same for the the other study, ah they don't see the their dashboard. They only see the speed. So they're not influenced, but they i need I should be running at like 16K per hour. They just go, oh, I'm feeling how I should go.
00:38:51
Speaker
ah And ah just to talk about the the core core sensor, as you said, ah people usually put it on the earth-rate strap, usually on the left, like ah slightly ah on the left of the the chest. ah And it measures two two things. So it measures skin temperature and also the heat flux. ah So there's a skin temperature sensor and an heat flux sensor. yu And it's connected to your ah approach rate and with an algorithm, ah it estimates your core body ah temperature. yeah That's an important distinction. It's not a direct measurement. There's nothing i see yeah inside your body cavity measuring the actual temperature. That's that's why ah I think it was our other study that maybe is going to be published
00:39:43
Speaker
ah It's really interesting because a lot of people are using internal cooling strategy like drinking cold call fluid or drinking slush before an event. But because the core sensor only measure the skin temperature and drinking cold fluid or drinking slush has no impact on the temperature of the skin. ah as As we saw in our in our this study, ah the core body temperature after drinking a small amount of of water dropped a lot, but the
00:40:19
Speaker
The estimated core temperature didn't change at all. So that was the first result of the study. And also the second finding was that it underestimated by about almost 0.5 degrees Celsius, so 0.47 degrees Celsius, also during the So the, sorry, the course, the external, we got to use, because they're both course and they're measuring core temperature. Yes. Okay. And then let's say skin sensor and GI sensor for the sake of listeners. So the skin sensor, if I understand correctly, underreported the findings of the GI sensor by almost half a degree. Is that right? Yeah, almost half a degree, which is, was just quite a lot. And as we saw like during the,
00:41:14
Speaker
Uh, when they drink, they drink water, their, their GI temperature decrease, but the the skin temperature didn't, didn't change a lot. Uh, so in actual like competition, uh, condition, like people would maybe if they, they, they followed or the skin sensor, the estimated temperature, reture they would think that, Oh, the cooling strategy is not really working pretty well. So, uh, that's an issue. And during the.
00:41:43
Speaker
the 5K, there was a mean ah estimated temperature difference by almost 0.5 as well. But there was a good correlation. So when when core body temperature increased during the 5K, the estimated temperature, the skin ah base estimation also increase. So that's why our fighting and why what we talk about in our discussion is that people can still use the the sensor knowing that there's a slight underestimation.
00:42:19
Speaker
yeah the The problem is that at really high temperature, like maybe if you're at 39 degrees or over that, 0.5 degrees is a big ah big d difference.
00:42:31
Speaker
and maybe so if your actual temperature is 40 degrees but you're the you're estimated what you see on your computer it tells you 39.5 that's a huge difference and that can actually push you to ah to eat stroke if you continue if you your only feedback is from your It's from the estimated temperature. We've also got our answer our own internal temperature sensor. so your Your body is busy. Exactly. I don't care what my garment says. if i'm If I'm dying, I'm dying. yeah there there was um There's two instances that come to mind for bypassing that thermal thermal limit thermal governor. um so One was, I can't remember the athlete's name, it was a pro-female triathlete who basically collapsed.
00:43:17
Speaker
Sarah True, yes. She collapsed right before the finish line, I think within a kilometre of the finish line um on an Ironman. So very close to the end, but she overran herself. And then I think during the Commonwealth Games actually in Australia, there was a Scottish marathoner who was leading the marathon and he fell, just collapsed due to a heat stroke right near the end of the race as well. so There are some people in the rare case who who can push themselves to that level, but I think it's it's very uncommon. Most people, will their bodies will tell them to stop before, or they won't physically be able to push themselves. The the rate of perceived exertion is too high to to be able to to push yourself beyond that. yeah like what we so like There's ah some studies like in
00:44:07
Speaker
in the laboratory and like with regular people and like the people would stop the like the time trial for exertion at like 38.7 degrees Celsius. So their thinking was that the critical temperature was maybe like 38.7. But then when your actual athletes competing for to win a major competition, first of all, you want to win.
00:44:33
Speaker
There's the spectators cheering for you. There's also money involved, the sponsors. like There's quite a lot of external factors that push you to
Using Core Sensors in Extreme Conditions
00:44:42
Speaker
push even more. And athletes, if you're at the eye level, or are used to push, like to not listen to that to that voice that tells you to to slow down. So that's when thats that becomes an issue. And that's... ah Yeah, it's not the... like Even if like blue man fell one, the Tokyo Olympic games, we also in cro finished across the finish line, uh, fall down collapse. He had to be taken care of in a wheelchair. It was like, it shows like I'm curious what his core body temperature was, but it was definitely over 40. I'm pretty sure. So yeah, that's a, that's an issue. And that's, that's why I think that, uh,
00:45:24
Speaker
for long-duration ah competition ah like a marathon and an hour man it's quite useful to to know your your temperature when you're racing because you act, you can actually gauge your effort, maybe slow down a little bit. Whereas like during the Olympic games, especially for like ah a 10 K run, he's still going to push himself. Even if it's a temp core buddy estimation tells him it's a, he's a 41 because he won wins. But we, we see that, uh, in a, especially our men, the, the American is,
00:46:02
Speaker
is the the time is fast, but it's not that fast. There's there's a lot of ah pacing involved ah dealing with the eat, and especially if you can make sure that for the... us the first 30 kilometers of the marathon. yeah You don't run, maybe ah you always keep your body under 29 degrees Celsius. And maybe you can tell yourself like for the last 5K, it doesn't matter. I'm just going to try to maybe push to the finish ni and we'll see what happens after that. I'll just take a i called ah cold bath after that. But to to pace yourself, that can really
00:46:42
Speaker
help yourself to to make sure you so you stay in the right zone the same way that ah when you're cycling, you stay in the right power zone. I feel like more and more with the device that are becoming more ah reliable ah for ah core body temperature estimation, a lot more people are going to use it.
00:47:01
Speaker
and In our computer, when they're cycling or when they're running, there's going to be their pace, their power, and our core body temperature. And they're are always going to look at the all three to make sure that the they don't push their body too too much. And personally, I think that would be the that's in warm condition. that the one measurement that's the most important, even more than like Earth rate or or your pace, you know? Yeah, you can design a pacing strategy for sure around that where you can say, you know, you can set limiters, like that's a common thing to where you will say, okay, this is where your target power is, but if heart rate is above this, then you got a throttle or in the in this case, it would be if
00:47:40
Speaker
um temperature, core temperatures above this, you can throttle. But I want to spend a bit of time talking about that, um sort of the the the concept you brought up about absolute accuracy versus repeatability. Because you were saying earlier that the court the the external core sensor, the the skin sensor tracked um it ain't the The value increased um you know of it correlated well with the GI sensor when they during the 5K time trial. So um in a sense, my my question with this technology is always, is it useful and how can I use it?
00:48:16
Speaker
And it sounds like you can make a use case for this external core sensor, even if the absolute reading is different. and But maybe sometimes it fails, like when you were talking about absolute temperatures, when you know you have to stop at you know ah temperature X. So um in your in your opinion, having used this, can you can you make a use case for it where ah knowing your core numbers right versus maybe you don't know what your absolute numbers are because you can't afford a pill. You can't get a pill. But you know what you know how far you can push yourself ah you based on the numbers that you see from your the the skin core device. um Can you come up with a pacing strategy based on that? Because you you whether if you believe that it's repeatable, if you believe that the data um correlates well with your actual internal core temperature.
00:49:10
Speaker
Well, my my opinion is that, well, then the longer the duration, like our study was quite short because it's a five kilometer time trial, you know, and the increase in temperature is super, super high. You know, I feel like, uh, like they,
00:49:28
Speaker
The beginning of the effort and the core body temperature is quite low, like maybe closer to like, well, the resting core body temperature, like closer to 37 and it increased super fast in a short amount of time.
00:49:42
Speaker
Let's say like 20, 25 minutes, but for, if you're like a lot of cycling class cyclists use it for like five, six hours duration races. Uh, and our core body temperature is going to, is not going to fluctuate that much. Uh, so I feel like when there's not that much rate of change, uh,
00:50:04
Speaker
ah So what we've seen is that the problem with the device is when our actual core body temperature or GI temperature has changed a lot. ah It takes a bit of time for the the skin temperature to adjust itself. But when there is not that much fluctuation, is especially especially if you take ah like ah the the medium for a six hour race is still going to be pretty pretty close and that can still give you a good idea. But as the the duration is shorter and the rate of change of temperature is is a lot bigger, ah that's when the the issue of ah correlation is becomes harder.
00:50:45
Speaker
ah because the the change in temperature is quite quite a lot. Interesting. So I feel like for longer events, when there's not that much change in pacing, there's not that much change in so in temperature, it's still a good ah good device. ah But the problem is like in a cycling race, even though it's a five or five or six hour race, there's still going to be some attacks. There's still going to be some climbs. And that's when the the court body temperature fluctuates a lot too.
00:51:17
Speaker
And I think I've seen some data from races where everyone's cruising along. They're going quickly. you know Their power output's still high. But then they get to a climb. And all of a sudden, you've got reduced airflow. You've got slightly higher power. um So all of these things happen at the same time. And then your core body temperature shoots way up. um But according to your study, as long as you're not ingesting a huge amount of cold water, that should still be tolerable from the sensor. It should still be able to provide a good representation Yeah, because when you're you're drinking during the race, your goal is mostly to hydrate yourself. It's not like you're doing ah a pre-cooling strategy before a time trial. Our issue or more, like if before a time trial, ah people were ingesting
00:52:06
Speaker
sludge, which ah quite a lot of cyclists do. Well, the core well the sensor is not going to well estimate the real temperature. Then is that again because that that that core temperature changes very quickly when you ingest sludge? No, it's just because the The sludge reduces your internal temperature, so your temperature in your actual core around your stomach, but it has no impact on your your skin temperature. No, but eventually that's going to you know it's going to diffuse through the body, right? Yeah, it's going to take some time, that's why. Yeah, so it's similar to your working muscles producing the heat when you're when you're exercising intensely, and then that also takes some time to diffuse, I guess, to the skin.
Future of Core Temperature Monitoring
00:52:52
Speaker
And I feel like what's interesting now with those type of technology is that the algorithm always changes. And so at first there were there was the same algorithm when you were sitting versus when you were doing a physical effort. okay But now they've changed the adapt. So there's two different algorithms. So when you're sitting and when you're doing a physical effort.
00:53:19
Speaker
And I feel like, because at first, you didn't need to have the to connect your heart rate when you were sitting. and Now, it's in our study, we use the heart rate all the time. But I feel like ah if the device becomes smarter or and the company grows a little bit, there there might be some option to to specify maybe to specify what's your weight, what's your surface area of body.
00:53:45
Speaker
ah what type of activity ah you do, ah because some studies that that were done ah to validate the ah device were done in cycling, but it's not the same when you're running. ah So if you could specify, oh, I'm cycling, maybe the algorithm is going to be slightly different than if you specify that you're running.
00:54:05
Speaker
ah Also, and there might be like an option to to say, oh, I'm using a cooling strategy. I'm using an internal cooling strategy, or I'm using IZVES. And that's another issue. If you have the the sensor and then you're putting an IZVES on the it, well, that's going to skew all the resolutions. It's going to cool down.
00:54:26
Speaker
but ah That's what's interesting with those type of devices. Without the the device actually changing, that the algorithm and all the different options can improve ah so that the accuracy can and and improve.
00:54:43
Speaker
As you were saying that, there are things going through my mind like, oh, you could hook it up to your bike computer having the environmental temperature feed into it. You could have your power your bike power feed into it. yeah um Things like that that could help their algorithm. so And because Ironman is largely a steady state event, you're not you're not surging, you're not having big attacks or anything like that. They could probably really fine tune that algorithm for a specific trajectory. There you go with sensor integration stuff again, Andrew.
00:55:10
Speaker
And I know if you've seen, Alden Norwegians are using the those sensors, and they they're working closely with the the company Core Green Tag. And Norwegians are putting like a core sensor on their forehead. there They have a few on their arms, some on their legs, so and obviously on the chest to see a different... because One of the issues, like we we think our core body temperature, but our body is not the same throughout our yeah our body. like If you take your core body rectally versus isophagus, it's not going to be the exactly the the same temperature. So ah that's interesting to to have like those type of device at different places. But I feel like the way they use it is they don't really use the estimated body temperature.
00:56:01
Speaker
They mostly only use the heat flux and the skin temperature, ah which is something that's available when you have like the i think its the scientific scientific version of the of the device, not the one that most people purchase. Yeah, not the commercial version. And because they they work closely with with them, they ah they can have access to everything. Because if not, people could actually try to to see what's the actual algorithm that they're using and just copy their their product. But that's kind that's actually interesting interesting to no ah ah to know that it it flux at different places on the body. That's why they they use it to to test the thermodynamics of their trisuit. They're developing with Surpass. So yeah, that's that's really cool. Yeah.
00:56:49
Speaker
Yeah, I think there that that there was ah this was a long time since I spoke to the core folks, but they were they were talking about how when they do product development, like and I think they were specifically talking about Surpass then, is that they do use an array of sensors. They're not using a single sensor. So to your point, and what we see the Norwegians doing is using that array because they must have they must have ah an algorithm that is that takes multiple data points and gives you maybe a better ah big picture than a single sensor would.
00:57:17
Speaker
And i've I've actually taken some thermal images of myself while I've been exercising. And it's amazing to see the variation in temperature over the course of your body. And it's with sweat and evaporation, your skin surface temperature changes significantly depending on where you're looking at. Especially because also your muscle is the the muscle that produces the heat. So if you're cycling, your quads are producing tons of heat compared to maybe or your forearm or doing basically nothing. Every part of your body is at a different temperature, but the mean is that yeah your overall temperature is quite warm.
00:57:56
Speaker
Yeah, and like you were saying before, if you're generating a thousand watts of waste heat for 300 watts of ah mechanical energy, then that heat has to come out somewhere and it makes sense that the muscles are generating the vast majority of that. For sure. um So Antoine, this has been great. Thank you very much for for coming on the show and spending some time with us and and and sharing the information from your studies. It's a pleasure to meet you too. Like I like i said in the intro, I followed you for a little while now. um Appreciate it.
00:58:24
Speaker
I can't believe we haven't spoken before, to be honest. um We are so similar. Yeah, especially like, you know, ah somebody at that at a very high level in the sport who's also studying the sport. That's always, that's like a very good, you know, Venn diagram intersection of who who we want to be talking to.
00:58:41
Speaker
And now that I've discovered a podcast, I'm definitely going to listen to a bunch of them, too. Yeah. Nice. Awesome. Well, thanks so much. And listeners, um you know keep coming back. We're still going to talk about cooling for a couple more episodes, and then we'll be back with a regular mix of of nerdy endurance topics. And I suspect at some point, Antoine will make a second appearance here. Yeah, it'll be a pleasure, yeah. Thanks for listening, everyone.
00:59:11
Speaker
but That's good. I'm rusty with my English for now. soon Better than our French. Oh my God. Heaps.