Sports Science Dudes

Episode 100 - Sit In A Tub, Run Like A Rocket with PhD Student, Elliott Jenkins

• Jose Antonio PhD

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We talk with physiologist Elliot Jenkins about how passive heat acclimation boosts VO2 max, hemoglobin mass, and cardiac function in trained runners without adding mechanical training load. Practical protocols, safety tips, and open research questions round out a clear, actionable guide to using heat wisely.

• Elliot’s path from Otago to a PhD in the UK
• Why passive heat instead of exercising in heat
• Hematology: plasma volume expansion 
• Cardiac changes: larger end-diastolic volume and stroke volume
• VO2 max and speed gains in trained runners
• Practical protocol: time, temperature, frequency, hydration
• Safety: dizziness, slow exits, supervision, low blood pressure
• Dose-response unknowns and hot-climate athletes
• Heat vs cold and contrast for recovery and adaptation
• Where to find Elliot’s paper and social links (see below).

Follow Elliott Jenkins on X @E_J_Jenkins 

His paper is published here: https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP289874


SPEAKER_00:

Uh welcome to the Sports Science Dudes. I'm your host, Dr. Jose Antonio. And with me today is Elliot Jenkins. He is a Kiwi physiologist from I know I hope I'm pronouncing this correctly, Christchurch. Is that right? Yeah, that's fun. Christchurch, New Zealand. He completed his undergrad degree at the University of Otago, or is it Otago?

SPEAKER_02:

Otago.

SPEAKER_00:

Otago. Okay. With uh Professor Jim Cotter before moving to the UK to start a PhD at Cardiff Metropolitan University with Professor Mike Stembridge. Uh his work sits at the intersection of exercise and environmental physiology, exploring how heat and altitude influence human performance. And sort of what got me in peaked with your bio is that you're interested in altitude, but you're in the UK, which has like no altitude.

SPEAKER_02:

Yeah, there is, I don't think there's any uh mountains above a thousand meters here. Um but uh back back home in New Zealand, we have a few more peaks above that, uh about that above that number.

SPEAKER_00:

Do you suspect you'll be going back to New Zealand when you finish your PhD?

SPEAKER_02:

Uh long long term, I'm thinking yes, but um maybe there's a postdoc somewhere uh kind of in between and and the uh and the time being.

SPEAKER_00:

I know there's a lot of postdoc availabilities in the US, so that might be something for you to consider. And if you're interested in altitude, you know, we got the Rocky Mountains, which uh Yeah, yeah.

SPEAKER_02:

Uh one of my good buddies works in um in flag staff, like Arizona as well. So they know they've got uh a big kind of altitude community there as well.

SPEAKER_00:

Yeah, it's a beautiful area, absolutely beautiful area. Now, before we start talking about your paper, um, I do want to mention to the audience since uh let me just pull it up real quick. Um, the title of your paper is Long-Term Passive Heat Acclamation, Enhances Maximal Oxygen Consumption via hematological and cardiac adaptation in endurance runners. Obviously, for the endurance world, this is interesting. But before I get to that, I'm always interested in how you decided to pursue a PhD because when I talk to you know recently minted PhDs and how they made that decision, it's all completely different. Uh, versus like, you know, medical school. Well, my doctor dad was a doctor, so I thought I'd be a doctor, you know, that kind of thing. So how did you come to the decision of yes, I want to pursue a PhD, and yes, in this this particular area?

SPEAKER_02:

Yeah, so I think um back when I was an undergrad student, I had this kind of uh goal in mind of just working in high performance sport. I wanted to um to I wasn't good enough to to could be an athlete myself and kind of compete in that world. But um, if I could get a job working in the high performance uh kind of space, then um that that'd be something I could see a lot of value and kind of enjoyment in. Um but it was during my undergrad that I got uh involved in a heat acclimation study at the time as a as a participant. Um and in doing that study, that's when I met my uh who would go on to be my supervisor in Jim Cotter. Um, and he really kind of just uh hooked me on uh on uh research, kind of uh asking these these questions that um people uh may or may not have thought thought about before, but then kind of using that research to then inform what happens kind of in in the high performance world, right? Um so did did my undergrads um and kind of a year of postgraduate research with with Jim. Um and then during uh after that point, I wanted to um do some travel as well. So I'd plan to do a kind of uh gap year um in the year of 2020, which we all know um couldn't go ahead uh for obvious reasons. So um went back to the drawing board. Um, and then kind of when uh everything with COVID cleared up, um, I had a British passport um just by virtue of uh being born in the UK, despite being brought up in New Zealand. Um and Jim had worked with my new my now supervisor Mike previously, and they put me in touch and um yeah, kind of just never never looked back from the kind of research uh perspective. So where are you now in your uh doctoral studies? I've I've been telling people I'm one one year out from from getting my PhD.

SPEAKER_00:

Um I was doctoral students hate they always hate that question. It's like, well, when are you gonna be done? And it's like, I'll be done when I'm done. But but yeah, it's uh it's a long process, it's an endurance event, it's not really a sprint, that's for damn sure. No, absolutely not. Is this part of your dissertation, or this was just a fun process?

SPEAKER_02:

Yeah, this is uh this was study number one. Um so too more to come in this space, but um, this was the one that uh has definitely seen the most work go into it, kind of a big long intervention. Um, my next two studies won't won't be uh this this time intensive.

SPEAKER_00:

No, this is what I love about this study is that one, you you're measuring a lot of things, but two, there's a pragmatic application to it. And uh I assume you're an endurance athlete yourself? Yes, cane cane runner, yeah. Okay. So this has personal interest to you, obviously. My question is this if if you look at um in the US, because there's so many people who are in on social media and talking about exercise and fitness, the last four or five years has been this barrage of cold water immersion. You gotta get a cold tub and just sit in a in a in a tub of ice filled with water. And frankly, I've never been impressed with the data on cold water immersion. And frankly, part of the reason my wife and I moved to Florida is we like hot weather. We we we do not want to purposely sit in a tub of cold water. You know, we want to avoid cold at all costs. However, the argument always made against cold water immersion is I've never seen any direct effect on performance, even though people claim you perform better, there's none. Um some of my friends they do it because they say they feel less sore. Okay, maybe it decreases delayed onset muscle soreness. However, what piqued me about about this is that um the the change in MaxiO2 is interesting because these were trained runners, right? These are these are not you know slow pokes. So I guess the question is you're thinking about this before you do the project, there's some thought process in your head whereby you decide, well, maybe there's something to passive heat exposure that might improve performance or indirect measures of performance. So so walk us through that process.

SPEAKER_02:

Yeah, so um like I said, my uh kind of experience during my undergrad was and uh I participated in uh just what was a week, one week long heat acclamation um intervention, um and uh got the kind of the bug to research heat a bit more. Um so when I was thinking of of what to investigate during my PhD, I came across these studies by Carson Lumby, um, who has gone on to show in four or five studies now that uh exercise in the heat, so active heat acclimation, uh, for over the course of uh five weeks can improve uh or increase hemoglobin mass and improve exercise performance and VO2 max. Um and at that point it just seemed like kind of kidneck to the dots for me in terms of um it was being a no-brainer of okay, but do you need to be exercising the heat? But like I I knew from my own experience experience uh during that uh study I participated in that exercising in the heat is hard. Like it adds to your load, it um uh slows like decreases the intensity you can operate at. It's not overly comfortable. It kind of makes me uh compromise other training outside of that one heat acclamation session. So I thought, okay, can we use uh utilize a passive mode of heat acclimation? Um, and can we get the same benefits?

SPEAKER_00:

Yeah, well, obviously, living in South Florida, it's hot all year. So what's interesting is when endurance athletes compete up north, northern part of US where it's colder, um, they do a lot better in terms of times, just because there's no heat stress. And then vice versa, when cold weather runners come down to South Florida, they do very poorly because they just the heat the heat kills them. Your study didn't address this, but if you were to compare, get someone who lives in the northern parts of the United States where it's cold, they train the way they train, um, but they also sit passively in a hot tub. Would that be, and I know I don't know if you know the answer to this, or just speculate, would that be the equivalent of someone in South Florida just training in the heat? Is that sort of the goal you're uh you're trying to get to?

SPEAKER_02:

Yeah, so I guess the your your question is more around the kind of traditional or what we typically consider traditional heat acclimation outcomes, where um you intentionally exercise in the heat or you sit in a hot bath so that when you come to compete in hotter environments, you're better prepared. So uh looking at adaptations like a decreased resting core temperature and increased sweat rate, um uh your thermal tolerance is improved. Um and that has been shown from a from a passive heat perspective. Uh, I think the one one study that's coming to mind is uh post-exercise hot water immersion being this kind of uh complete uh or a more effective method to induce a more complete kind of heat acclimation profile so that when you come to exercise in the heat, you're you're um kind of better adapted.

SPEAKER_00:

So now you had mentioned uh post-exercise heat immersion might be the best um I guess protocol for this. Is that because well you're hot to begin with, now you're inducing more heat stress?

SPEAKER_02:

Yeah, I don't that's um just off the back of this study that I've I've read in terms of uh yeah, you're already uh raising your core temperature via exercise. Um obviously it depends on kind of the ambient temperatures you're working in, but um so even say even if you just complete a 30-minute easy run or easy bike ride, you're gonna have metabolically induced uh increases in your core temperature, whereby then if you sit in a hot bath after that, you're prolonging that increase uh without necessarily having to raise it from baseline.

SPEAKER_00:

Now, remind me, uh refresh my memory in terms of your data. You found, I believe, an increase in is it hemoglobin? And was it also hematocrit? I'm not sure.

SPEAKER_02:

Uh hematocrit follows a kind of a phasic response where uh initially, after one to two weeks of heating, you get an increase in plasma volume. So hematocrit decreases, um, after which point what we believe to be your crit meter is sensing that decrease in the hematocrit, um, which then causes an increase in your red blood cell volume. Um so hematocrit actually pre-to post is exactly the same, but overall blood volume and hemoglobin mass has increased.

SPEAKER_00:

So blood volume goes up, which ironically, um I mean, isn't that and you'll have to refresh my memory with endurance training adaptations. When you get untrained people who start to endurance train, is uh is the blood volume increase or plasma volume increase one of the initial adaptations?

SPEAKER_02:

Yeah, so plasma volume uh increase differently. Um it's we know that uh plasma volume fluctuations are part of the acute response to exercise. So uh during exercise, you undergo plasma volume contraction, subsequent to that you have an overshoot or a plasma volume expansion over time and an untrained cohort. Yeah, like you say, that plasma volume will increase and your overall blood volume will increase.

SPEAKER_00:

Now, what's the mechanism for getting that increase in red cells um from heat exposure?

SPEAKER_02:

Yeah, so this we we're not entirely sure of yet. My study can kind of partly address that uh that question, but what it uh our data indicates is um what's being termed as the crit meter hypothesis, where within your kidneys uh a um sensor called what's being called the crit meter uh recognizes or uh measures your hematocrit. And when it gets too low, it uh suggests to your kidneys to start uh increasing their e uh APO synthesis to increase your red blood cells. Um so after one to two weeks of heating, we've got this big placer volume expansion. Your uh crit meter is saying, hey, we need to we need to increase our red blood cell uh volume to get our hematocrit back up to kind of an optimal set point.

SPEAKER_00:

Interesting. Now looking at your Max VO2 data, and I like that you put uh individual data points here because I noticed with MaxVO2 the uh I think the control, basically nothing. I mean, slight up, slight down, no change, but everyone in the when they were exposed to heat, it looks like one, two, everyone improved except looks like one person did not. Um which is interesting. Do you think based on the actually some of these guys some of these guys have a very high max VO2? What kind of athletes were these? I mean, there's a guy here with 82. Holy geez.

SPEAKER_02:

Yeah, one of one of our participants is a two hour 12 marathoner. Um so it was really cool to get kind of uh someone that elite through through the study. Um say most people were were sitting around that mid-60s VO2 max kind of number, so 664, 65-ish. Um, and then yeah, we had one uh particularly elite, elite runner.

SPEAKER_00:

Now, what do you think this would translate to of let's say they'll run a 5k or a 10k um in terms of seconds off? Because that's a lot of runners or even cyclists would say, well, what's that mean in terms of seconds? I mean, you'd have to guess because you didn't do a time trial, but you know, what would you think?

SPEAKER_01:

Hmm.

SPEAKER_02:

Um we're probably in the in the realm of of two to four percent, I would say, maybe maybe slightly less than that in terms of a performance benefit. Um our uh VO2 max numbers increased by 2.7 absolute, which I think equivalent to about four percent uh uh from yeah, four percent increase from pre to post uh intervention. Um the only thing we can point to from an actual um uh speed perspective, uh, because we didn't get people to do a uh 5k before and after. Um the only thing we can point to is that the treadmill speed at VO2 max uh increased by almost a full kilometer an hour from pre-to-post um intervention. So um the speed that people were running at when they were maxing out is faster. So that itself would uh definitely help you in the long run of a of a uh distance running event.

SPEAKER_00:

I mean, that's really amazing, actually. Were you surprised that they improved that much?

SPEAKER_02:

Yeah, I like definitely I I had faith that this would work from the get-go. Um I knew we would see, I say new, I would, I was uh confident we would see increases in hemoglobin mass. I was somewhat surprised by the increase in um uh left ventricular and diastolic volume and kind of the cardiac adaptations.

SPEAKER_00:

Actually, let me stop you there. Explain that because a lot of the audience, they're not familiar with cardiac physiology. Explain the the importance of that.

SPEAKER_02:

So um when we talk about left ventricular and diastolic volume, we're talking about uh the size of the chamber of your heart when it's at its biggest. So when it's uh just be just finished filling. So you've got a filling phase and a kind of an ejection phase during um every heartbeat. Uh the left ventricular end diastolic volume is essentially when your heart is the biggest. You've you've just had the um influx of blood from uh your left atrium, uh, your left ventricle, your left ventricle is as big as it's gonna be, it's ready to shoot all that blood out um into uh the the rest of your body throughout your aorta. So um having a bigger heart allows you to pump more blood out per beat, essentially, and that's more oxygen being carried around to your working muscles. So if you can uh effectively uh increase your oxygen delivery by way of increasing that kind of stroke volume, um that's gonna serve you well kind of for for exercise and maximal exercise.

SPEAKER_00:

And that end diastyl volume is a function of blood volume since blood volume took. Yeah, interesting. Now let me ask you this. You know, living in South Florida, I'm I'm exposed primarily to endurance athletes. My wife's a competitive cyclist. Um, I know a lot of do athletes and and triathletes, but my main sport, the one I I say I compete in it, I guess I compete in the master's level, but um is outrigger canoeing and stand-up paddling, which are sort of weird endurance sports. They're not like running, I guess they're closer to rowing, um, where your body weight is supported. So you don't have issues per se with a heavier body weight, if as long as you can produce power. So my question is this training in South Florida, it's hot all year. I mean, oddly enough, we don't think we think it's kind of cool now, which if you can do the conversion to Celsius, it's about 78 degrees Fahrenheit, which is like, wow, it's kind of cool out, which I think to most Europeans are like, wow, it's kind of hot out.

SPEAKER_02:

Um but my question is UK right now.

SPEAKER_00:

Yeah, yeah, we we train outdoors all year, so we're always ex we're always exposed to heat while training. What do you think adding more heat, like because we're always hot to be honest? Now we're adding more heat, we do passive heat exposure, you know, hot water immersion. Theoretically, that should help as well, right?

SPEAKER_02:

Yeah, it's a really interesting question. It's um something that the current data can't really um give any kind of extra uh point to because every every lab that's done these studies, uh I say every lab, that's only three that I'm aware of, including our own. We're we're based in uh in pretty uh cool climates. It's us in the UK, you know, our our summers can get as hot as low 20 degrees. Sorry to the American audience who uh only knows Fahrenheit. Um but uh it's yeah, it's not it's not particularly hot. And then uh past in Lumby's lab is in Scandinavia, so uh even colder than where we are. It's it's very um it's in places where even in the summer, we're probably not seeing temperatures as as hot as you have in uh Florida in the winter. Um so whether you'd get you'd see these same adaptations in people who do train in heat all all year round is a is a really good question. And um something I don't think we have enough data to um be able to say outright uh yet.

SPEAKER_00:

Well, here's a here's more of a pragmatic question because athletes will try things before a lot a lot of times before there's data. Would there be any downside to passive heat exposure or hot water immersion in Florida where it's hot all year? You're an endurance athlete, you train, you're doing all the right things, you eat well, you're like, what do you know? I'm gonna buy a hot tub, I'm gonna sit in it. You I think your protocol was five times a week, 45 minutes. Is that correct? Yep. If I added that to my training, would there be a downside to it? Or is it it's either has no effect or a possible upside?

SPEAKER_02:

I I haven't observed a uh downside yet, um, kind of in all of uh our participants. Um one thing that we also did throughout the uh study was we got general uh perceptual well-being scores, kind of by virtue of asking people about their muscle fatigue, their overall kind of uh training stress, their uh feelings of soreness, their like how tired they are. And uh between across both conditions, so during the hot water immersion and the control, uh, there was no no difference in those kind of perceptual scores. So um people felt the same whether they were adding an extra uh you know, like say five by 45 minutes of of hot water immersion to their training versus no uh uh just kind of control, the control conditions, so not not doing those things. Um so uh it's not affecting them from a uh perceptual um standpoint. You are getting these massive uh benefits. They the only thing is kind of time uh how time consuming it is. Um there are um I guess I guess we might we might come to this, but there are potential um risks involved. 45 minutes in a 40 degree uh hot bath is a long time. Um and what happens during that time is uh your blood vessels vasodilate, you send a lot of um uh blood to your skin to try to keep you cool. When you come to hop out of the bath, if you immediately stand up uh and try to stand up too quickly, uh you you your brain, which has hasn't had as much kind of uh uh blood flow, wants to send the signal for you to get back to being horizontal as quickly as possible. So the way it does that is uh by essentially making making you fall over, or you might feel dizzy, you might uh um kind of black out in uh it's called heat uh syncope.

SPEAKER_00:

Um did that happen with any of your uh study subjects?

SPEAKER_02:

We definitely had people who were dizzy. Um we were pretty um strict around a kind of gradual um exit from the tub. So sitting on the side of the bath for a good five minutes before then drying yourself off and um move moving um or moving to stand and kind of walk around. Um but yeah, anecdotally I've heard of a lot of people kind of forcing the issue a bit too quickly and then um either slipping because it's you know the hopping out of water or um yeah, uh kind of having this uh orthostatic intolerance and going going down.

SPEAKER_00:

Would you um not recommend it for those with low blood pressure? Because we've had I mean in our lab, just as a matter of just being you know, thorough with athletes, a lot of times we'll just measure blood pressure. And a lot of female athletes, at least at the college level in the US, it's not uncommon for it to be 90 over 60, um, 100 over 70. I mean, low, definitely a lot lower than males. Would what concerns would you have for someone like that?

SPEAKER_02:

Yeah, I'd just be extremely cautious. I think um athlete kind of monitoring is is hugely important. I would never suggest for anyone to do this unsupervised. Um it's just something we you uh you want to know that someone's kind of watching out for you as you as you kind of sit in these environments. And for someone who was uh hypertensive um to begin with, I'd uh yeah, I'd suggest uh taking it extremely easy. Don't don't don't don't at all go for 45 minutes, right? Um or acquire acquire a bit more tolerance as you as you get on. But um the piece around um having a slow and kind of steady exit um is is more important for that population.

SPEAKER_00:

Okay, pragmatic question. Does it have to be 45 minutes? Could it be less? That's number one. 104 Celsius, 104 cells, no, 104 Fahrenheit or 40 Celsius, can it be lower than that? Or that's sort of the threshold? You have to be 45 minutes five times a week at 40 degrees Celsius.

SPEAKER_02:

Yeah, so um the your first question around uh 45 minutes as it does it have to be that long. I would say no. I'd say uh we don't know super well about dose response yet, but I would say um 45 minutes is probably at the longer end. I think you could probably see benefit from uh uh 30 30 minutes, doing this five five times a week, 30 minutes a day, or even uh dropping to three or four times a week. It's um if you're a serious athlete, this should be about supplementing your training. It's not as a replacement of training, it's it's there to uh serve to accentuate um uh your already strong training stimulus. Um and if that means you can only get fit in yeah, three or four uh heat sessions a week, um, then that's great. Um not getting to five isn't gonna isn't gonna hurt you. Um temperature. And then yeah, the temperature point, um we started people at 40 degrees, so 104 and uh degrees Fahrenheit, and then we kind of titrated or we uh set temperature for the remaining weeks, um, kind of basing it on thermal tolerance, so how or uh thermal discomfort, should I say? So how people were feeling in the tub. And because you acquired this thermal tolerance with typical hair acclimation, that meant we got up to almost 42 degrees by the end of the five weeks or roughly 107, 108 degrees Fahrenheit, I want to say.

SPEAKER_01:

So um I would say it's really hot.

SPEAKER_02:

It did it did get hot for people. Um, I would say start at what feels uh or start at what feels like you can sit in it comfortably for the first 10 minutes, and then it might start to feel uncomfortable. If you don't get beyond 15, 20 minutes the first time you do it uh at that temperature, that's cool. You hop out, come back the next day, you'll have more tolerance the next time you you go, you go for it. Um and you'll be able to kind of extend that time out. I'd say you you definitely want to be at least above um core temperature. Our rest in core temperature is about 37 degrees. Again, I'm I'm sorry, I don't know exactly what what that is in uh degrees Fahrenheit, but you want it to be higher than uh core temperature, and then I would say as a to keep it as a progressive stimulus, um, slowly dial up that temperature as as you go. Um don't at all feel like you have to go above 42 degrees because yeah, it was hot for people.

SPEAKER_00:

That is hot. So so 45 minutes is sort of at the top end, you can maybe drop it to half hour three or four times a week. Um do you have anyone who's who would want to do any of these athletes who said I want to do this more than 45 minutes? And is there a is there a diminishing return or is there no return after you know five times a week, 45 minutes?

SPEAKER_02:

The the um people were definitely not asking for more. Oh I was um I was definitely in the in the in the first instance, I was uh having to um really try to manage people's kind of uh feelings around uh wanting to wanting to hop out a bit early, which we were which we were fine with. We knew they would develop that tolerance. Um But the I guess the nice thing about uh doing these heat sessions in a in a bath is you have a lot of behavioral changes that you can do to get yourself through 45 minutes, so taking more of your body out of the water essentially just to uh get yourself a bit cooler, or any of these things to to get yourself that 45 minute mark.

SPEAKER_00:

Um how much water would you would you recommend while sitting here? Or because obviously the heat stress is less the more you drink, but yeah.

SPEAKER_02:

So we um we gave people 500 mil of water across the um the 45 minutes, so uh that being the upper limit. People could drink less if they wanted to. I don't think many people did. Everyone always had the the 500 mil. And the reason why we capped it at 500 mil is because there's research to suggest that uh dehydration additively enhances your plasma volume expansion. So uh uh if you get uh if you lose more fluid across the 45 minutes, uh that will give you a bigger bang for your buck in terms of uh the resulting plasma volume expansion 24 hours afterwards, say. Um so we we wanted to make sure people were finishing the sessions dehydrated without making it uh impossible for them to get through the the sessions itself. So that kind of 500 mil mark ended up working quite well. Um but in that I would say uh 500 mil is also just a number we've we've pulled out of uh kind of um necessity. Drink drink to thirst. Um if you're thirsty, drink. Don't uh drink more than you have to. Um but uh yeah, if you if you need to for uh to get yourself through those sessions, get have have some nice cold water nearby.

SPEAKER_00:

Okay, uh very good. Okay, uh just a few more and then and then you know we can wrap this up. You had one female subject, nine male subjects. And I know you can't really answer this based on a N of one, but would you expect any sex differences in terms of the internal difference?

SPEAKER_02:

Not based on the uh findings of so I I've mentioned Carson Lumbey's studies already. Um he has one that has looked at uh sex differences in uh long term hate training studies, um, and found that there there wasn't any, but uh it's worth, I guess, the caveat of that is um They were doing exercise in the heat and not the passive approach like we did. So can't really speak to it too much on our own data, like you say. There is another paper that's looked at acutely, kind of after following one hot bath, looking at sex differences and the EPO response to a one one session at 45 degrees, sorry, 40 degrees, 45 minutes. And they they do see a sex difference that and kind of the EPO response to that one to that one bath. But uh yeah, whether that then translates to across the five weeks, uh, we don't know. So it's it's still a question that's up in the air and um uh for unfortunately one we can't answer at this stage.

SPEAKER_00:

Interesting. Final question, it's really more for you to speculate. Not so much the differences between hot water and cold water immersion, but there are a lot of individuals, at least in the US, that basically do hot, cold therapy. They'll get in a hot tub, then they'll get in the cold tub, and they'll just sort of flip back and forth. Um, I would I personally just find it painful, so I don't do it. So what would be the adaptive response to sort of this extreme of hot and cold immersion? Um, what do you think would happen, or nothing happens?

SPEAKER_02:

Uh I I can't I probably can't speak to that from a long-term basis. I know that the um people do it for recovery, right? That they want it to let their muscles feel good. Um, and I I think I agree with you kind of the things you said off the top of the show in terms of um I've I've not uh been convinced by any of the cold water immersion data that's come out, and I guess that includes contrast therapy. I've not seen anything that suggests contrast therapy is any better than just hot water immersion on its own. Um I can't uh give any uh kind of additional thought to um or um credence to contrast therapy as a um as a mode of um effective recovery. I actually think I saw a uh a paper in the Journal of Physiology which suggests that uh hot water immersion is more effective for muscle recovery uh after kind of simulated musculoskeletal injury um than cold water immersion. Um so I think more and more of the data is backing heat over over cold from a acute recovery perspective and now from a uh kind of long-term um uh adaptation response as well.

SPEAKER_00:

There's certainly an irony to that, uh, you know, considering how popular cold water immersion has become. Um and anyone who's ever sat in a hot tub knows that it just feels a lot better. Even if it's really hot, it still feels better. So um, well, Elliot, I want to thank you so much for being on the podcast. Uh, I want to remind everyone who loves science. I mean, this is actually the science is great, pragmatic application. It's uh your uh study was published in the Journal of Physiology. Again, long-term passive heat acclimation enhances maximal oxygen consumption via hematological and cardiac adaptation in endurance runners. Um, I don't know if you are you on social media? Do you do you have uh uh X account on Instagram?

SPEAKER_02:

You want to follow my uh my upcoming research. Um, I'm on ResearchGate, just Elliot Jenkins, um, cut me. I'm also on uh Twitter or X E J uh Jenkins. Um you can find me on there.

SPEAKER_00:

Awesome. Well, thank you so much. This has been really eye-opening, and I think a lot of people will, you know, they're gonna be bugging you about this study because uh because the data's cool. And you know, I I applaud you. Uh this is actually one of the better PhD student studies I have ever seen. So congrats on that. Appreciate it.

SPEAKER_02:

Appreciate it.

SPEAKER_00:

Hey, thank you.