Hot Water Immersion and Overtraining with Sam Oliver & Robbie McIntyre | KoopCast Episode 170

trail and ultra runners what is going on what's happening welcome to another episode of the KoopCast as always i am your humble host coach Jason Koop and this episode of the podcast is coming in with some new findings on hot water immersion for heat acclimation those of you training for the badwater 135 the western states 100 or even wasatch surely recognize the need for heat acclimation training in order to improve performance in those events however there still remains a chasm of practice among coaches and athletes as to what types of interventions to use whether that be exercising in the heat the use of a sauna or the use of a hot water immersion bath and even how long to use those interventions for in addition to this it has long been contentious amongst coaches and athletes about how stressful these types of interventions are and i have made my opinion very clear on this aspect that many athletes and coaches continually miss the mark when they choose to run around the mountains in their puffy jackets or use a sauna for months on end fortunately for athletes more and more research continues to point out that sensible heat acclimation protocols that last

days not weeks and interfere little or not at all with the training process continue to come out and this podcast is a further extension of that theme so enter sam oliver and robbie mcintyre whose recent paper which is titled a comparison of medium term heat acclimation by post-exercise hot water immersion or exercise in the heat adaptation overreaching and thyroid hormones and i know that's a mouthful but this research paper pits hot water immersion against exercising the heat in a control group and compare those modes effectiveness and if they have a difference in contributing to any of the ill ill effects of overtraining syndrome i love how the research like this can produce simple logical extensions into everyday practice and preparation for athletes so that they can perform at their best so with that as a bit of a backdrop i'm going to get right out of the way here's my conversation with sam oliver and robbie mcintyre i'm always really curious to talk about a topic such as this because it's so incredibly prevalent in ultra marathon running which is going to be our primary audience that's listening to this not only do we have like a number of uh a number of races that are hot weather races where the environment becomes one of if not the limiting factor but in addition to this and i make fun of the ultra crowd

about this all the time there's just this legacy of ultra runners doing all of these contrived and crazy uh methods and uh adjunctive types of training and interventions to try to overcome the heat and whether that's exercising in a sauna or layering up with you know 10 different layers or doing a combination of all of those and even more it just kind of gets more bizarre so those two things combine the fact that the races themselves or there are a lot of races themselves that have hot weather types of environments where it becomes a critical issue but also this kind of legacy of all this crazy type of training it makes the research that we're going to talk about today incredibly prevalent but before before we get into it just so the audience can kind of learn uh learn voices to names and to learn a little bit more about you let's take some time and just introduce you guys uh and and just generally what you do and what your research focuses on and i guess since my green box is around sam sam you can uh kick us off here oh thanks jason so my name is sam oliver i'm a a reader i guess associate professor on that side of the pond um in sport exercise science here at bang university in in wales in the uk um my work my research and teaching really centers around um exercise and environmental physiology um and a big part of this has been developing strategies to really improve people's um health as well as their performance operates that have to operate in these sort of extreme

environments so athletes for sure are a big focus but also some other active populations like soldiers um other allied health professionals that are working in like mountainous environments for example so yeah and looking forward i'm you know looking into the future i'm really keen to try and use some of the things we've learned um in these populations to try and help better prepare the general population for some more extreme weather that's likely coming our way so the heat waves and and cold snaps that are often in the news so yeah that's that's where we're at and here in the u.s we're trust trust me we are completely accustomed to using our military personnel for these types of uh for these for this type of research they're great guinea pigs and very willing willing guinea pigs to put them in extreme types of uh environments and just where i live in colorado springs colorado there's actually a kind of a plethora of that because we have the mountains and we have the cold and we also have the military bases here so a lot of that research tends to it tends to emanate just really proximal to to where i'm living so i'm sure you can you can appreciate that um uh so let's continue on robbie you want to introduce yourself real quick yeah thanks jason thanks for having us on um yeah my name is robbie mcintyre uh background in exercise physiology and uh last year i've completed my PhD which specialized in heat acclimation so comparing different strategies to prepare for exercise in the environments and that was partly funded by bangor university and the ministry of

defense i'm now a lecturer at st maire's university in twickenham london um where i lecture on exercise physiology so the paper that we're going to discuss and that'll eventually spider out into some conversation because it's always important to discuss the like literature the link to this will be in the show notes for the uh for the listeners but the title of it is is a comparison of medium term heat acclimation by post-exercise hot water immersion or exercise in the heat adaptations and the i think the critical piece of this that is unique in in this space is overreaching in thyroid hormones and i want to center a little bit of the conversation around that because as practitioners in the space one of the things that we are very consciously aware of is that whenever we put an athlete through a heat acclimation protocol there is this push and pull and give and take between the training load and the heat acclimation additional load that is put on that athlete and we're always searching for this goldilocks type of scenario to where we can maintain the training load as much as possible because we realize that that's incredibly important but we also want to add on some type of intervention that is going to have an effect either an altitude type of effect or in this case a an effect in in hot weather environments and i'm not i'm not aware of a lot of research that can kind of like quantify like how stressful

the heat acclimation part of it is we recognize that it's stressful we were either in a passive environment or an active environment and one of the unique traits of your research in particular was trying to kind of aim at like how it might be additionally stressful when you're just adding these types of interventions on and if and is there a way to actually do it more uh more effectively so either one of you can kind of take it from here i want to first just generally describe the study setup in terms of who you were looking at and the intervention that you that you were putting them through and what specifically you were looking at with uh with the subjects yeah i'll go for this um so we recruited recreationally active males and that was sort of um the equivalent to like a military personnel like military recruits who are often most at risk of exertional heat illness and these sort of uh performance decrements because they haven't maybe been exposed to that sort of heat before um so that was our uh study population and what we were doing was comparing uh conventional excise heat acclimation intervention with um a more novel post-exercise hot water immersion approach um we've previously seen adaptations from post-excise hot water

immersion over the short term so looking at three to six days um but what we hadn't uh investigated yet was extending that and seeing whether extending the six-day post-excise hot water immersion protocol to 12 days would lead to greater adaptations which is um often reported to be the case with uh conventional exercise heat acclimation interventions so we wanted to extend the protocol to 12 days and assess um heat acclimation adaptations and compare those between post-exercise hot water immersion and exercise heat acclimation and as you've said we wanted to also look into maybe some of the if we could elucidate some of the mechanisms behind the adaptations from heat acclimation so we set about uh trying to measure um thyroid hormones and we also were quite interested in looking at the overreaching element to it as well and comparing between those two interventions and for the audience just as a little bit of a clarification i think we need to be a little bit more specific on what the exercise heat acclimation or the traditional way as you're calling it of heat acclimation what that actually means like what were the athletes actually doing for that are they exercising in the heat are they overdressing like how did that actually look in the in this uh paper yeah so uh we wanted to sort of replicate uh normal guidelines which is just to

exercise in the heat um so normally what athletes would do is to travel out to hot country um and complete like a training camp there for a week two weeks and then travel back home um or they could also travel uh exercise in an environmental chamber which is like a hot box sort of idea and we can control the environmental conditions so increase the temperature of the room and exercise there um so what we did was uh the participants would exercise at a sub maximum intensity for up to 60 minutes in the first six occasions 75 minutes in the next six occasions 30 minutes in 33 degrees heat 40 relative humidity that's hot yeah a lot of sweat was a lot of sweat during that protocol okay uh sam anything you want to add to that no not really i think robbie's just done a really good job that i described in the uh trying to call i think the key the key message here is we're really trying to compare uh historically what people have um thought of as being the kind of optimal kind of prolonged 12 days two weeks of um exercise heat acclimation whether that be in a chamber or whether that be in a natural environment so this new form of this maybe more practical of

exercising in a cool environment but then taking that um hot hot bath afterwards um to try and act as a a heat additional or different heat acclimation strategy so that's the rule was there was there any reason that you guys were using hot water immersion as opposed to a dry sauna so it comes from uh background studies so mike zeralu and new walsh jessica me uh released a few studies a few years ago from 2016 2018 2019 looking at post-execisal water immersion so we knew from those studies that it was effective in recreationally active and endurance trained individuals so and the results looked really promising um so we thought that was a a good option to go with yeah i'd add on to that one there jason that um it's a really it is from that practical sense i guess a sauna you you need that sauna environment not many people are lucky enough to probably have a sauna at home but most people have a bath or something they could have a tub or something that they could fill with hot water and sort of recreate this in their own environment so um from a practical perspective it probably is more practical than like a sauna type strategy certainly much more practical than having a thermal or environmental chamber for you to to do this yeah excellent and i've seen you know we've used both of those methodologies in practice and i would say the balance of it always comes out on uh on sam just

what you were mentioning what's the most convenient for the athlete right because when you try to tease out the differences from a from a physiological point of view or from an outcome point of view between those two methodologies you kind of get into this hair splitting type of competition and you've got to go back to is it easier just for the athlete to fill up their tub with hot water boiling water some sort of combination of those two or drive to the gym get in a dry sauna you know go from their car to the gym get in the sauna come out and then kind of go on with their day that's a whole you know hour and a half right of additional time that they've that's kind of evaporated so i think your point to from from from a convenience perspective is actually uh is actually really well taken i want to get into some of the over training component of this uh of this particular paper that you guys wanted to study because i think this is one of the things that makes this relatively unique in this whole heat acclimation space and also brings us back to the question of from a practical point of view what intervention is going to be best what type of intervention is going to be best depending upon the situation of the athlete so what were you measuring from that perspective and why did you choose to measure those markers so we looked at a number of different measures uh including sleep uh cognitive function and um uh what was the three measures sam well you did the performance test itself

right so the exercise test itself is a it's pretty much considered one of the sort of methods to be able to try to sell whether someone's not performing as well um blood lactate is a sometimes kicked around as potentially as a marker in relation to the exercise capacity that was also assessed as well um and uh mood of course which is probably the um probably the most simplest right way and i'm guessing jason as a as a coach and yeah i'm guessing you probably get most from speaking to your athletes and finding out how they're feeling and probably that's the biggest indication if you've um you ramped up that training a bit too quick or it's been going on for too long at a high level and then really my my understanding of the over training literature not as not specifically of heat acclimation is that mood is probably one of the most sensitive markers so so um robbie did a good job in assessing that in in the participants in this study as well and that's the one that i wanted to pick on a little bit i'm so i'm so glad that you mentioned that sam because you you you you've already extrapolated what i was going to mention is is from a pragmatic uh point of view whenever i've put athletes through these protocols and you can talk to any coach out there they're just run down i mean their their mood is literally depressed even you can hear it in the tone of their voice when you get them on the phone or you talk to them after a workout and it's because of the stress of the heat intervention whether you're using whether they're exercising in the heat or you're

using a sauna or hot water immersion which is what you guys were using in this particular study and so i'm so glad that you guys tried to encapsulate that as well because it's a sentiment that we've had in the coaching world for a long period of time but we've had a tough time like scientifically explaining it or scientifically kind of like moving through is this actually is this actually something or are we kind of biasing it with our own you know through our through our own lens and through our own experience so let's start to move through through the results and i kind of you guys can direct on what you think were the most important things from and and the most powerful things from the actual research itself and then we can kind of discuss what those mean for the athletes so robbie i think you'll probably take the lead on on on this piece of it what within the results of the actual study did you kind of find like the most most important that athletes should actually start to pay attention to so for heat acclimation key adaptation would be a reduction in end exercise core temperature so that's core temperature we use rectal core temperature which is gold standard um but yeah core temperature at the end of submaximal exercise in the heat um and that adaptation really lends itself to performing in the heat uh because that tends to be the limiting factor and when you reach a core temperature of yeah 40 degrees then you're starting to go into heat stroke and

your performance uh heat exhaustion that sort of thing so um that's like a key adaptation to uh heat acclimation and it's yeah one of our key results from this study a reduction in end exercise core temperature and uh resting core temperature as well um so we saw quite large reductions um following six and twelve days of post exercise hot water immersion um and end exercise core temperature and resting core temperature and it was a significantly uh a significantly greater reduction in uh both of those from uh just the exercising in a temperate environment and then exercising in the heat as well um yeah so that'll be our main one i think sam do you want to tack on to that yeah only to maybe point something out which is maybe in comparison with some of the previous studies that as robbie rightly pointed out were led by professor neil walsh and mike zerala the early papers in this sequence of studies one of the additional things we did in this study is we started to look at not just core temperature but also the whole body's temperature using a metrical mean body temperature which is mathematically derived from the peripheral skin temperature and the core temperature combined and um in this paper we actually showed that that was also um reduced the whole mean body temperature of the individual more

after post-exercise hot water immersion in comparison with the um conventional heat acclimation strategy and the reason why i picked that up that might you might sort of say well sam you so it sounds like it's splitting has core temperature yeah yeah so i'll pick that up a little bit more as the way i i like to think about it is that if we just focus on core temperature we might be missing the the total benefit of interventions um whether that be heat acclimation or some other form of preparatory strategy to uh for people working they're going to go and exercise in heat so if we take another one say like um ice slushy is one that some people have knocked around so you take your ice slushy it drops your core temperature but i'm not aware of whether you know whether that's really going to have any effect on your periphery whether that's actually going to reduce the whole body's temperature and i think one of the really additional steps in this study is we've shown that post-exercise hot water emotion leads to a reduction in the whole body temperature which if you think about it when you start to exercise if the whole body is cooler you've got a great you've created yourself a greater healing heat uh greater ceiling sorry before you heat up to those higher core temperatures and it and there's some although it's somewhat debated some people actually argue that it's not really core temperature alone which is the limiting factor for exercise performance in the heat it's actually a combination and maybe just as much it's just as important to think about skin temperature and how hard our periphery is um when

we think about what causes us to stop um exercising so yeah like i said i think that that additional bit of information it might be missed when people read the paper because they don't quite get the subtlety between assessing the core versus the whole body temperature and but i think that that additional bit of information is really um suggests to me even greater benefits really of post-exercise hot water immersion than perhaps we've previously appreciated um in the in the earlier work yeah i think that that's super important because i remember when everybody jumped on the ice slushy bandwagon for it seemed like a six or 18 month period of time when that initial research came out and then we all took a big step back and said wait wait a minute maybe this doesn't have as big of an effect as we thought it did and then maybe in certain conditions you're actually being counterproductive to what you're trying to do because the cold that you're ingesting is so highly localized in one area of the body and not to say that you can't combine an ice slushy with other types of cooling uh interventions but it a lot of people in my in my opinion my professional coaching opinion got blinded to utilizing one as kind of the sole sword in that fight that they that they were having uh against the heat not realizing that there are other kind of other things at play so you're the the salient point though with this with this particular

study is what you're and what what you're trying to to communicate that i'll reemphasize is maybe with the with any type of heat intervention we should appreciate both the reduction in core temperature as well as the reduction in total body temperature and perhaps hot water immersion can affect both of those which is a larger benefit than just the core temperature reduction um i'm i'm gonna take a moment and let you guys regroup here and direct the listeners to a previous podcast that i did with the u.s olympic training center's uh lindsey golich who's been a colleague of mine for a long period of time and has done these core temperature uh studies on any number of different athletes we had a great conversation about that and the specific protocol that she uses there at the training center to test core temperature increases uh with all of these types of athletes y'all go and check that uh y'all go and check that podcast out if you want more information on how we how they actually test this uh in the lab and some of the protocols that are actually used which is slightly different than you guys's protocol but it's going to hit the general gists so we'll move back to robbie here we've got this core temperature change right which is to be not not to not to uh belittle the research paper but it's kind of a no duh right that's what you expect there's a lot of literature to suggest that any any of these types of heat interventions are going to have that type of effect let's roll it down a little bit more what else did you find that was that was interesting that might be important to athletes we saw also saw reduction and it's maybe another obvious one but also saw reduction in a

perceptual um or an improvement in thermal comfort in the heat after post-exercise hot water immersion um and so that's probably also so that's obviously with ultramarathon stuff and the mental game is a big part of it especially as distances uh increase it becomes more and more psychological right and so a reduction or an improvement in perceptual comfort is uh yeah is what we observe following post-exercise hot water immersion um and alongside that uh an improvement in rating of perceived exertions so the participants found it easier to work in the heat after post-exercise hot water immersion compared to just training in a temperate environment Sam do you want to tack on to that one at all well i think the the perception of effort is key right the thing that makes us stop exercising is when it cuts too tough that we decide to quit yeah um on my big one of my former uh mentors uh professor samuel and markora does all the work on mental fatigue and endurance performance um you know he he made that pretty clear and when i was uh when i was back in the student and i still hold on to that you know rpe it's a really simple measure just like we're talking about mood scales and things but it's really um it gives us some really good insights so i think again it could be really overlooked in this particular paper

it's just rpe but it's practically and for athletes and coaches it that date is really important that we're showing there that we're reducing people's perception of their their their exercising effort and and that means that they're going to be able to exercise for longer um at the same intensity and and clearly that's super important for for any um endurance athlete uh so yeah simple but uh really meaningful uh finding samuel's uh legacy has extended throughout the throughout this podcast probably in about a dozen different episodes so i'm sure you didn't know that beforehand but if you go back through the guest list they're just they're just kind of everywhere so yeah i mean i i'm i'm kind of on the same page as we can measure a lot of these end physiological effects from heat interventions but what might be the most important and probably performance powerful of all of them is just i feel cooler the heat doesn't affect or i feel that the heat doesn't affect me now whether that's who knows what that's due to right some sort of physiological effect that that is not kind of translating uh or is not as impactful kind of up the uh up the neural chain or just the fact that they have done it and they get a psychological boost from knowing that they've gone through that protocol and that they've done the work or a combination all those i kind of don't care if you feel like you're going to perform better in the heat because you've gone through the intervention great i'm going to take that win you know six ways from

sunday and we're going to just we're just going to absolutely absolutely run with it um so that's super important as well and we we hear that feedback from our athletes is they just feel more prepared and the the the important word that i'm trying to emphasize there is feel they feel more prepared after going through these types of interventions because you can't really placebo control it right you're either in the sauna or you're not you're in the hot water immersion or you're not it's kind of it's a binary thing right you can't you can't fake it you can't fake that type of work you're going to do it or you're not um so i want to move on to some of the like overtraining parameters that you guys measured because i thought that this was interesting and it's certainly a little bit more nuanced but as i mentioned in the very beginning of this podcast it's something from a from a coaching perspective and also from the athlete's perspective that we try to put a big highlight on because athletes don't want to stop training they just want to add on whatever intervention it is right whether it's you know a heat acclimation intervention or an altitude intervention or even a strength training intervention they always want to add and not add and subtract something else and we've tried to find this goldilocks scenario across the whole host of training interventions that we have in our toolkit heat acclimation kind of being one of them and you guys are trying to get a little bit at this answer in

terms of how impactful this this could be what did you find out in this in in this area because it is something that's subject to debate and something that's a lot more that's it's certainly a little bit less clear than some of the other uh and physiological goals that you can measure yeah i think it's a difficult one it's it's often overreaching is often overlooked and heat acclimation research literature you don't you don't often see um overreaching markers measured um there are a couple of studies that have looked at overreaching after like an intensified heat acclimation training program and shown that after a period of recovery there is an additional performance improvement uh so that sort of tells you that there is a bit of a decrement after exercise heat acclimation um but yeah to our knowledge i think this is the first uh study that's looked at overreaching markers after post-exercise hot water immersion yeah i think um a strength of studies we used the a lot of different measures to try and work out where the participants were overreached at the moment i'm not aware of a singular overreaching measure um in existence because there's a lot of ambiguity about uh when does a when's a an individual become overreached and how to measure that so we used a lot of different measures to track a lot of different aspects as i've said including uh mood cognitive performance uh endurance performance sleep and

also looking at end exercise heart rate and uh blood lactate um and yeah after 12 days of uh post-exercise hot water immersion 12 days of exercise heat acclimation and 12 days of exercise and temperate environment we found that there weren't actually any differences between those interventions in terms of overreaching markers so that sort of shows you that um even though that these participants had done 12 days of this heat acclimation that they weren't shown much sign of uh overreaching so i mean kind of what i take from that is is that either one of the interventions are tolerable and you know one of the one of the things that i think is really important to to point out to this is you're using a you're using a group to where the extra they're not trying to exercise at their absolute maximum right their training protocol is not certainly set up to their maximum like their maximum capacity and whenever that's the case you can layer on additional training some sort of additional intervention or in many cases both and it kind of becomes a nothing burger and so i'm always quite cautious to interpret some of these to a high performing athletic audience because this the important difference in my in my estimation and you guys can bat this around a little bit is the difference in how hard they are actually training compared to the

maximum amount of training load that they can actually tolerate during a training cycle and with high performance athletes they're so close to that ceiling that anything that you kind of layer on top of that whether it's an additional hour per week of training in whatever mode or some sort of intervention then that's when actually it actually becomes important because they're so close to that ceiling a lot of times when we're looking at other population groups and even though they're doing the same type of training some of those just things don't show up because they can tolerate the increase in stress because they're so far below the maximum amount of stress that they can that they can actually tolerate and so your point to where other studies have pointed this out that there might be some sort of contribution of a heat acclimation protocol to uh to any sort of over training or overreaching markers however we wanted to find it and yours didn't show that it quite as quite as powerful i think that a lot of the difference lies in who you studying and how hard are they training during the actual study compared to what their maximum is yeah i think that's a really good point um we were working with recreationally active individuals and um they were probably using this or they were using this protocol was their main training that week for example so they weren't going off and doing another session that evening and so it was probably uh they were probably able to recover during that time um adequately enough sam do you want to jump in and tack on to any of that yeah the only thing i would say is i i agree as

well jason i think that um uh understanding the uh merit of post-exercise hot water emotion in really elite athletes um perhaps we don't have the hard evidence on that but i think some of the um earlier studies by uh zarali the first author he did we you know in that study there is some data there and some people who are more endurance trained that the their vo2 max escapes me maybe robbie can remember what how how fit those individuals were in the in the endurance train group but they were pretty well trained and doing pretty reasonable number of hours so there is evidence that the post-exercise hot water immersion strategy is effective in um more than recreationally trained athletes not maybe in world class or super elite types we have maybe haven't got that evidence yet but um certainly in in fitter individuals and i think the only other bit i would tack on is that remember that um the the exercise intensities were individualized um in each of these studies so that they're they are a percentage of their vo2 max so um in application in really elite runners i i i don't see why we wouldn't think about prescribing it in that way i guess the only might and and then i would say that it might be effective and we would avoid the overtraining potentially in that group i guess for you jason it's about is that enough intensity are they happy with that or do they do that do the strategy and turn around and say i just didn't feel like i was

running as hard today i know it was in the heat but i kind of wanted to run harder is that starting am i losing something else from my training so i think having a look at the actual it could be individualized is what i'm saying and i think it could be done in it could be just as effective in more um you know in in higher uh higher level runners cyclists whatever you name it but um we probably just need to to keep that in mind really yeah because the tendency of most athletes i guarantee you this with 20 years of experience doing this stuff is they just want to add and not substitute irrespective of the intervention or whatever type of training that you're introducing they want to add it to what they're currently doing right i mean it kind of goes back to the original concept of progressive overload right you always want to keep overloading the body overload overload overload overload but with really good athletes or really experienced athletes you're kind of at the top of how much you can load them you're just in in a lot of senses training becomes a game of how you organize the the load throughout certain periods of the year in just a smarter fashion maybe not in a more fashion just in a smarter fashion and this becomes one of those elements where you're adding a particular type of load but in almost all cases except for the cases where your athlete is kind of like for whatever reason maybe they're injury limited right so they're undershooting their maximum load that would be a case where in in your research

actually is a really good would be a very good proof point of this to where you can just add the load on top of it and there's probably no consequence but it's when the athletes are at the maximum amount of their load that's when it gets really tricky in adding any additional load whether it's heat acclimation altitude strength training whatever you want to what kind of whatever you want to add so anyway i my encouragement to athletes is to just look at how close they are to their maximum and see how much they need to like take off the table almost nobody wants to do it it's like it's i could tell you from a practitioner's point of view it's a total arm wrestling contest to get to people to reduce like three percent of their volume to add on heat i mean it is a really really really big fight i think one of the things uh just coming in there just to sort of come to me whilst we're talking about that is one of the other really neat early findings um from 2019 one of again mike's earlier papers is he showed that this heat acclimation um effects from post-exercise hot water motion lasts for at least two weeks so i guess why why i'm um i'm putting that out there is just for people to think about when you time this and and maybe there's an opportunity then to heat acclimate increase that load that stress but not worry too much that you could actually then afford a couple of weeks of uh recovering before a major event and you're still going to retain that heat those benefits of the

heat acclimation two weeks after you've finished um your heat acclimation period so that might just allow some flexibility both for coaches and athletes to think about where do i put this in i know it's going to potentially increase my load i'm going to feel uh pretty crappy feel a bit more tired but i've got a couple of weeks probably we actually don't know how long it lasts that's a study for the future but um at least two weeks is our best guess at the moment so um yeah i think that that's worth bearing in mind for for athletes and coaches yeah to that point you see you guys have probably seen this work out in practice but many of the coaches and athletes in the space are starting to favor a two-phase protocol where they do like the heavier hitting or the more important phase like six or eight weeks out from the event and then have a two-week phase in between to where they're just training and then that's their highest training phase right so there's no heat acclimation they're just training as hard as they can that's the four to five or six weeks out from the event and then they come back closer to the event and then just do a little top off that's maybe 75 or 80 of the heat acclimation protocol that they do before and then leave a little space to to to the race and then that two what that two phase protocol it's kind of doing two things first off is you're getting the first major bump far enough

away from the event that if you screw it up which happens you know if you haven't done it before it happens you don't know how you're going to react to the heat right i mean that's there's a huge individual response and those of you guys that are watching the youtube version can see these huge nods from robbie and sammy you guys recognize that in the research right there's a huge individual variation in terms of how hard and how impactful these kind of things are so you do the first one far enough out from the event so if you screw it up you got a little bit of time to course correct but also you're not doing it at the same time as you're doing the heaviest load of training so you stop the heat acclimation then you do your heaviest load of training what in my opinion makes that more impactful because it gives you a little bit of a bump from that and then you come back not having lost much if anything to your point sam uh and you do a little bit of top off kind of coming coming back into the event so i've just started to see that being favored a little bit more in practice versus what we originally used to do which was just to stack it all at the very end and roll the dice and go to the casino and see if it actually ends up working a little bit of a reckless fashion but um so i'm glad that we're starting to see some of this research really elucidate that that kind of two-phase protocol and practice because i think the research and the practice that's one of those areas where they've kind of been running along the same tracks for a little bit and they're a little bit in agreement as the research starts to develop i'm gonna i'm gonna end this i'm gonna put you guys on the spot a little bit since we're talking about the pragmatic points of it and you guys can coin flip on who

who takes this one first if you had an ultra marathon athlete and an endurance athlete approach you on on just how to do this i'm training for a hot weather race hot weather marathon ironman triathlon they're going to kona or something like that the bad water 135 can you just give them a really high level overview of the protocol that you would use and be kind of specific i'm gonna i know you guys don't like this because it's it starts to get into the theoretical but try to be specific as you can on the duration of the exposure the intensity of the exposure and the duration of the entire protocol i think those are the things that the athletes are the most interested in when should i get in hot water immersion or sauna how long should i do it for on each session and how how many total consecutive days should i actually do it for are there any just generalized protocols that you can throw out to the audience based on your research and experience that that the audience can draw from probably robbie goes first yeah yeah so looking at like a single session um i think you'd start off with like an easy training session to get that initial rise in core temperature and then you're trying to get into the bath as soon as possible after you finish that training session um bath should be about 40 degrees c and you'll try and maintain that during the duration of the immersion and make sure you get up to your neck and fully submerged um and in terms of duration um starting off at around 20 minutes on your

first first immersion see how that goes but obviously listen to your body um if if you feel really uncomfortable then get out and you don't don't want to put yourself at risk because as soon as you stand up you know if you ever stood up quickly after if you're uh if after being in a bath you'll notice you get a bit of a head brush so uh be out be aware of that sort of thing um but yeah start off nice and easy 20 minutes and then next session maybe increase that by five minutes and then just see how that goes um and then in terms of the protocol duration and i think you're pretty safe going with six days we've got loads of evidence supporting six day immersion um we have shown a nice nice uh nice adaptations after three days of post excise hot water immersion but as you've said already it is very individual so three days might be good for someone but to um a higher chance of getting the adaptations that you want i would go with uh lower risk six days um and see how that goes sam anything to add to that no i think robbie's got that covered off really well i've really stressed the idea that because a lot of these people are really motivated individuals as you've already um indicated jason they kind of don't want to drop stuff and they may read well they may misread that these were 40 minute baths

and they have to do it for 12 days and and and although some people do get to those sort of lengths of 40 minutes after a number of days it's really important in that first couple of days um to to to to moderately exercise you're not coming in absolutely cooking hot after a really high intensity um session and jumping into a you know a bath which they then go yeah i'm gonna make it hotter still it was 40 degrees as good you know surely more is better so it's really a case of following the the advice of moderate exercise 40 degrees for the bath monitor it look for you know maybe up to 20 minutes on that first immersion but see how you get on if you're starting to feel like i can't stand this heat you need to be thinking to to come out even earlier than that and build it up over a few days and if you have somebody who's in and around supervising you know even if it's uh you know your partner or whatever at home i think that that's advisable as well because probably the biggest risk here is as you get up you you your um your legs are all dilated your your blood's in your lower leg especially fit trained um endurance athletes have got that you know that big vascular uh system in their in their lower limbs that you you are potentially going to you know just getting up with you get changing gravity and and pulling the blood in the legs and you're going to feel a bit dizzy and it's going to be slipping over in the bath that's going to be the be the downfall for people if they so getting out of the bath sitting down quietly for a few minutes afterwards because you're going to feel hot anyways you know just taking it easy since we have an ultra

marathon audience you have to indulge me with one final question or one final opinion i can get from you guys and and i'm sinisterly hoping that this also helps uh my conversations and the battles that i kind of have to fight when i'm when i'm explaining this particular aspect to athletes you both mentioned that six days is probably enough and that 20 to 40 minutes is probably enough not 60 days and 60 minutes which is what everybody wants to do when and the reason this is important for specifically for an ultra marathon audience and endurance athletes in general is they always think more is better right more miles more intervals more days training more weights in the gym more sessions more is better there's this like we think that there's there's this linear dose response relationship with everything so why six minutes sorry why six days and 20 to 40 minutes is there something deleterious or at least not as advantageous for going longer either in a session or longer for the entire protocol uh so per session i think um you'll probably be limited by like around the time frame of 40 minutes anyway um your because it's the bath temperature you want to clamp that about 40 degrees c your core temperature is

going to continue to rise until you get out so you can only take so much right um don't challenge these people because you know what's going to happen man people are going to email me after this podcast and say all right i'm taking that on don't don't do that don't do it you're i mean you're kind of taking it from a safety standpoint like people are going to tap out after after that period of time yeah just uh be be on the careful side i would say um especially in the first few baths like don't push yourself too much um um so uh our protocol was 12 days after the like um during the first six days we had a maximum duration of 40 minutes during the second six days so these uh so i mentioned seven to 12 we increased that maximum duration to 50 minutes i don't think any of our participants reached 50 minutes because their core temperature got so high um or they felt sick and had to come out yeah i think you're you're going to be limited by your core temperature and how you feel um but yeah i wouldn't i wouldn't push much much further than 40 minutes 45 minutes um from from a safety standpoint and and and i just add to that that remember um in this we were monitoring their core temperature during the moderate exercise that in temp in a cool environment before they got in so we knew exactly what core temperature people started

the hot water bath so that was my bit i was trying to make the point previous comment which is that if people do a really high intensity particularly high intensity short sessions where there isn't time for heat to dissipate away from the body they're actually the sessions where people's core temperatures are going to rise the most and actually you could be getting into the bath already with a very high temperature and then 40 minutes is definitely not going to be a good idea and 60 minutes is probably going to be dangerous so um unless you know your core temperature and you know your thermal physiology really well i think that um keeping with our sort of uh recommendations of building up slowly over a number of days doing moderate intensity exercise in a cool environment before you get into the hot bath remember and there's in the uk that's pretty easy it's pretty cold most most of the time but i know there's lots of places in the us over where your base where past the year is going to be really hot so people are going to be already really hot potentially before they get into the bath and i think the other bit i would just add on to this is that in the protocol after um uh four or so baths there was a rest day in this protocol so um in in the study that we're talking about so this isn't every single day without any form of rest so again it might be and this is speculative but if we tie this with some of the other papers that have shown some overreaching problems with heat acclimation um it could be that if you do this sort of thing every single day for 12

days or more and you're going up into sort of four weeks or whatever you might start to increase your likelihood of getting some form of overreaching etc so um maybe putting in a rest day isn't such a bad thing within even a six-day protocol where you just don't do one hot bath so um and at least we haven't shown that that having a rest day is having a negative effect on the the adaptations that are beneficially happening so i think that's important to uh to stress really yeah it's a relative the the hard thing that endurance athletes have a the thing that they have a hard time wrapping their head around is that most of the adaptations that they are seeking are chronic adaptations they take months to manifest you go and you do a training session and maybe that make most of those adaptations are going to show up eight weeks down the line right you have to train for months months and sometimes years to get better here the adaptations are very quick right they're a cute adaptations and so the tendency for endurance athletes is to think once again more is better longer duration is better if i do this more consecutive days it's better as well but all the literature is indicating that there might not only be a negative effect with doing it too many consecutive days or for too long of a period of time but also you can get like 90 of the maximum amount of benefit that you can study in a relatively short period of time and that's kind of what i come down to is like i'll leave the other 10 on the table because i don't want to spend another 30 days or however long that's going to take actually introducing this intervention and disrupting the training process and on and on and on leave

the last 10 on the table i can get the first 90 and whatever six eight nine days whatever you want to call it and just call it good yeah no that makes total sense um yeah i think you're uh the benefit you get off get from any heat acclimation protocol diminishes past a certain point so you reach a plateau in your adaptation and it doesn't matter how many more heat acclimation sessions you're going to do you're not going to get much of a benefit especially and it's not going to be worth your time not going to be worth the decrement in your training uh intensity and yeah could potentially lead to overreaching as well as we've talked about i think that that's a perfect way to to to leave it get enough dose and then just call it good at that point um thank you guys for this work uh like i said i've really appreciated it i i love it when i start to see like little nuances in the the acclimation interventions and also how we study the effects of those interventions and you guys did a brilliant job putting something together that's practical for a lot of people not just athletes that are undertaking these things uh we'll leave it with where can people find more about you and the work that you guys are doing sam you can go um well obviously just just google me sam oliver bangor university uk there's a there's a bio and and feel free to to reach out um the email address is there and um yeah

i'd like to particularly interested actually to hear like questions and things and from coaches runners and athletes because um i think often that that's those are the sorts of things that really stimulate um the minds of people like me that spend more of my time writing and doing science but actually you guys come up with some really good questions and um something you said earlier on there jason that there's this some of this research is starting to sort of support some of the thoughts we had and often i think that science was sort of we're always trying to play and catch up i think with some coaching uh ideas and things and eventually we helped to sort of support some of those things so we keep we need the questions from you guys um to keep us keep us in jobs i've always presented it as coaching we need to make reasonable extensions of the research because you know we're working with humans in an infinitely complex environment and science is trying to do the opposite right you're trying to take that infinitely complex environment and narrow it down to a few or several types of parameters and because of that conflict once again we're trying to logically extend what you guys are doing in the field great we've talked about this before in this podcast right you're studying non non-competitive non-elite types of athletes so we'll look at this and create a logical extension of what does this mean for an elite athlete if that's the context that you're that you're working with so absolutely i'm 100 on on board on this and i can guarantee you we're gonna have one of our coaching roundtables probably

in a few weeks on heat acclimation and we're gonna bring a study like this up as well as all the other you know supporting studies that have been out there and discuss what it means for athletes so 100 yeah definitely uh feel free to reach out i'd love to hear from any uh any anyone interested in heat acclimation want to know more you can find me on twitter at roly mac PhD or contact me via uh i'm at syd mary's university in twiccrum so yeah feel free to reach out and um great to hear from anyone links to both of those will be in the show notes appreciate you guys for uh coming on the podcast today thanks very much jason cheers jason thank you all right folks there you have it there you go much thanks to sam and to robbie for coming on the podcast today and also thank you for the research that you guys do i do continue to maintain the opinion that heat acclimation is one of the most effective interventions that we can use as coaches and endurance athletes and it also just happens to be one of the better researched ones and one of the ones that when you do right it can interfere very little or at all with the actual training process and one of the things that i hope the athletes and coaches appreciate about this podcast is the intervention doesn't have to be very complex it doesn't have to take a lot of time it doesn't have to take a long duration of days to actually achieve an effect thank you to all the listeners i hope you appreciated

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