In this episode of the Flex Diet Podcast, I sit down with Dr. Cas Fuchs from Maastricht University to dive into the science behind cold water immersion. We discuss its impact on muscle recovery, protein synthesis, and overall performance. Dr. Fuchs shares his latest research findings, debunking common myths and providing actionable insights for athletes and fitness enthusiasts. Plus, we touch on the effects of different carbohydrates on glycogen resynthesis and liver function. Whether you're a gym-goer or a seasoned athlete, this episode is packed with valuable information to optimize your training and recovery strategies.
In this episode of the Flex Diet Podcast, I sit down with Dr. Cas Fuchs from Maastricht University to dive into the science behind cold water immersion. We discuss its impact on muscle recovery, protein synthesis, and overall performance. Dr. Fuchs shares his latest research findings, debunking common myths and providing actionable insights for athletes and fitness enthusiasts.
Plus, we touch on the effects of different carbohydrates on glycogen resynthesis and liver function. Whether you're a gym-goer or a seasoned athlete, this episode is packed with valuable information to optimize your training and recovery strategies.
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Speaker: [00:00:00] Welcome back to the Flex Diet Podcast. I'm your host, Dr. Mike Nelson. On this podcast, we talk about all things too. Increase muscle, increase performance, improve body composition, do all of it within a flexible framework without destroying your health. On the podcast today, we've got Dr. Cass Fuchs. He is an assistant professor in the Department of Human Biology at Mastery University over in the Netherlands.
Uh, he conducts research on the intersection of exercise, physiology, nutrition, muscle metabolism and recovery. And what he is really known for is a lot of cold water emergent, in addition to everything from carbohydrate intake to protein metabolism, and a lot more. So today we're primarily talking about the effects of cold water immersion.
Does it really kill all your muscular gains? If so, by how much [00:01:00] does it really improve recovery? What are some of the pros of it, and what are some of the cons? Um, even if you don't use cold water immersion, I think you'll find this interesting in terms of, uh, some of the mechanisms that we talk about, uh, different ways you can potentially enhance your recovery.
Podcast today is brought to you by myself and my newsletter. If you wanna hop on the. Fitness Insider Newsletter, go to mike t nelson.com, go to newsletter and you'll be able to hop on there for free. I've got daily content to going out to you there. I also wanna make you aware that the Flex Diet Cert will open February 9th, 2026.
So mark your calendars coming up soon, and be open for one week, February 9th through February 16th. So the best place to find all the information is to hop on to the newsletter. I'll have a bunch more information coming out there, [00:02:00] uh, very soon. So, uh, pretty short today. And enjoy this podcast with Dr.
Fuchs all about the effects of cold water immersion.
Dr Mike T Nelson: Welcome to the podcast. Thank you so much for being here.
Dr Cas Fuchs: Happy to be here. Thanks, Mike.
Dr Mike T Nelson: Yeah. I guess we have to thank our friend, uh, DC or Dr. David Church for the, the intro. I'm sorry. You know him. No, I'm just kidding.
Dr Cas Fuchs: No, you should be sorry. I don't know. Good guy. I, I like him a lot, so.
Dr Mike T Nelson: Oh, he is awesome.
He has always the best, uh, referrals to you for the, the podcast too. 'cause he'll be like, oh, you have to have this person. I'm like, done. Like, whatever you recommend. Like, I trust you. So, and it was funny, he mentioned your name and I was like, oh, that's awesome because you were on my list when I did the physiologic flexibility certification.
I cited some of the studies you had done, um, in relation to cold [00:03:00] water immersion.
Dr Cas Fuchs: Mm-hmm.
Dr Mike T Nelson: Which I still think some of the studies you did are really interesting there. What made you even look at cold water immersion? Because it wasn't like you just published this study yesterday. It's, it's been out for a while and you were definitely ahead of the trend if you figure out when you had to, start conceiving the study, do the study, get it published, you know, all that kind of fun stuff.
Dr Cas Fuchs: Yeah, so the, the cooling thing, of course one of the main reasons to study this because I'm really interested in recovery strategies. Mm-hmm. And of course one of the main recovery strategies you would see online and, and with athletes is cold water immersion or these cryo chambers or cryos these days.
So basically cooling. Um, and the main question is a little bit like people say, okay, it's good for recovery, at least it's good for muscle recovery. That's what you always hear. Even if you talk to athletes who, who use cooling, they say like, ah, it's good for my muscle recovery. And you know, if you really look more deep into the physiology, like.
Maybe, but is it really that good? Because if you really [00:04:00] look like, how, how does that work? You at least I had some question marks on that. And also not just me, like more, I know more scientists and also with, with my professor, I discussed this in the past, um, and even like before I did my study, uh, there was some work from, uh, Australia for example, where they also saw that if you do long-term cold water emergence, so for 12 weeks, uh, after resistance training, uh, that they found that you kind of, you still see gains in terms of muscle mass and strength, but not as much as if you would not do the cooling.
So it kind of seems to be this, this thing of like, hey, maybe it's not good for everything in terms of recovery and or adaptation. Uh, so we were like, okay, thinking about cooling the physiological response you, you expect, you want, we see a drop in muscle temperature that's maybe not exactly that good, at least not always because that's something you actually want to maybe have a little bit higher after exercise for.
Optimal enzyme activity, et cetera. And also the, um, the [00:05:00] vasoconstriction that you get. So basically following exercise, we always, of course, ingest our meals to kind of, use our meals as a recovery way. And if you lower the ability to get those nutrients delivered by the muscle cell, that could actually impair the, the recovery process.
And so kind of those two mechanisms were interesting to us to see like, Hey, let's see what happens in terms of muscle protein synthesis, which is important for recovery as well as muscle adaptations. You,
Dr Mike T Nelson: oh, repeat that part again. You froze for just a sec. You said those are interesting because.
Dr Cas Fuchs: Sorry. So, um, was it about the temperature and the delivery of
Dr Mike T Nelson: the Yeah.
You said, do we wanna keep temperature a little bit higher afterwards and this helps with recovery and then it lost you for a few minutes there, or a few seconds
Dr Cas Fuchs: I'll just, they say it again. So yeah, you basically have the, um, the increase in, in muscle temperature following exercises is important for enzyme activity, for recovery processes and adaptation, and also the, um, the delivery of nutrients, right?
So [00:06:00] after exercise we eat meals. The meals will be used for example, replenishing glycogen. I think also something we may discuss later. Uh, but also just to provide amino acids to, to stimulate muscle protein synthesis, which is important for both muscle recovery as well as adaptations. And so we wanted to really focus on, on that specific aspect to see like, okay, so if we do.
Cold water immersion after exercise. What does, what really happens on, on muscle protein synthesis And kind of in line with the expectations, we found that, uh, you indeed impair your ability of stimulating muscle protein since compared if you would not do cooling. So you kind of are, uh, not in the most, let's say it's not the best.
Um, environment for the muscle if you do the cooling, at least from a perspective of stimulating muscle protein synthesis. So I think the cool thing about that is, at least I find, is that, uh, it's very context dependent and we should not always say like, Hey, let's do a recovery. Let's do this recovery study because it's good for [00:07:00] muscle recovery.
I think it's really important to figure out what's the goal of the, the, the recovery, uh, what do we want to even recover? And based on that, you can decide if, if it's a good strategy. And again, with cooling, there may be some reasons to do it still, uh, but also certainly some reasons not to do it depending on the goal of your recovery.
Dr Mike T Nelson: Yeah. And for listeners, obviously muscle protein synthesis, we'll link to some other podcasts. We've talked about that too. You're just kind of taking the amino acids and stuffing them back into muscle tissue to make it bigger and stronger, which I know that's a, a vast oversimplification of the process, but.
And then That's correct. Yeah. And talk a little bit about the parameters of that study, because I think that's where people go a little bit crazy. They, they hear that which is a correct, synopsis of the conclusion, but then they're like, oh my gosh, if you know, did it four hours after training for 30 seconds, seconds, you're destroying all your gains.
And it just seems to be like everything online [00:08:00] gets taken to the extreme without looking at, oh, okay, well what were the parameters of which this were done. If you want to talk a little bit about that.
Dr Cas Fuchs: Yeah, sure. People always wanna have a black and white answer. Right. And it's never really case. Yeah.
Dr Mike T Nelson: It's good or bad. Tell me if cold water's
Dr Cas Fuchs: good or bad. Yeah, exactly. Do I Sure I do it or not? Yeah. Uh, so yeah, in this study what we did resistance exercise, uh, one, one session at least. We actually have an acute study and a more longer term study. I'll tell that in a, I'll explain that in a bit, but Perfect.
The acute study design was one session of resistance training of the lower body. So del. Mostly focused on the quad muscles. And then following that, we actually put one leg in cold water for 20 minutes, and the water temperature was in degree Celsius. I think. Mike, you guys use Fahrenheit? I actually don't know the conversion.
That's okay. But it's eight eight degrees Celsius.
Dr Mike T Nelson: Yeah.
Dr Cas Fuchs: Yeah. I think it
Dr Mike T Nelson: is like a 47, 48 Fahrenheit. Somewhere in there. I, someone will correct me online and send me hate mail, but We'll, we'll figure it out.
Dr Cas Fuchs: People can look it up. So, so eight [00:09:00] degrees Celsius. Yeah. So, so pretty cold, of course. And the other lag we put also in water, so we kind of had both legs in water to keep that consistent, but that temperature was 30 degrees Celsius, which from like, let's say a water perspective gives you like a bit of, in the area of turmo neutral water.
Yeah. Uh, of course what 30 degrees outside feels warm, but if you're in water, it's actually, let's say comfortable. Mm-hmm. Um, and in that lack, we actually also didn't really see much changing in, in, in things like muscle temperature. So kind of, it was a nice control like. Uh, what we then did, we, we measured for five hours following.
Um. Uh, the, the, the cooling intervention. Uh, and immediately after the, the water immersion, we provided the protein shake, which actually also contains some carbohydrates. So basically like a recovery shake you typically see that people ingest, uh, in, in the field or in practice. Uh, and that contained also specifically labeled protein.
And what I mean with that is that we labeled the protein in such a way that we could really see how [00:10:00] much of the amino acids that were coming from the protein were being used and incorporated into new muscle tissue. Uh, that's a technique that we use here in, in Matric a lot. And so the cool thing about this was that we could not only just measure over these five hours in recovery muscle protein synthesis, but we could also see how much of what you eat will actually be used by the muscle to incorporate into making new muscle proteins.
And on both those aspects, uh, to make it simple, uh, we saw like that's the protein synthetic response. So that muscle protein synthesis in the cold lag was lower compared to the. Let's say thermo neutral lag. So again, you impair that ability to, to to increase, uh, um, or like you impair the ability for protein syn compared to a control condition.
And also you, we saw that l less of the amino acids that you ingest were being used by the, the lag that was cooled compared to the non coup lag. So you also can actually use less of what you eat in these first hours after recovery. Now [00:11:00] you said ferry correctly, it's always important to look into the context.
And this was again, doing it immediately after access also for 20 minutes, and also pretty cold. So of course, from a scientific point of view, for us, important to get like a quite a strong stimulus to see if there would be something. Because you know, if you do like a very, if you only do it for a minute and that like said 15 degrees Celsius, you know, and you don't see anything and you, you still don't know if, if there is something going on, if you do it like in like a, like a more, let's say stretching the practical duration as well as tempera.
So it was still practical, but it was let's say quite relatively long and relatively cold. If you would, and many people, like after that study also said like, yeah, what if you do it like four hours later? And you know that that's always dependent on how long you do it for, what's the temperature? Um, but I still think this study nicely shows that if you cool the muscle and you definitely, and you reduce your muscle temperature, we also see with recent studies that you indeed, uh, reduce your ability to, [00:12:00] um, to deliver the amino acids to your muscle cells.
Um, it's not necessarily beneficial for your, uh, for your recovery. Um, and maybe to add on that, like the longer term study that we did as well, to also see like, hey, it's nice that we see it in the first five hours, but what if we repeat this for seven sessions over two week period? So we followed this up with two weeks by which we use a different tracer technique.
It's called, uh, heavy water D two O. And what we could do with that is we could have those seven exercise sessions over over the two week period after every session, we did exactly the same. So one lack in cold water, one lack in turmo neutral water. And then we again found that over those two weeks that the protein synthetic response and the cold lag was lower than the control lag.
So it does also translate into longer term, which also makes sense if you think back about what I said completely at the start that Australia study, uh, were did for 12 uh, weeks and they, with MRI scans, so the goal started to look at muscle mass and muscle volume. [00:13:00] Uh, they found also lower gains, so it kind of all nicely lines up, which is definitely not always the case in science.
But this really was a nice addition to each other to look into the mechanisms on that.
Dr Mike T Nelson: Awesome. And the two week study, if I remember it, that was the same parameters as you used before, right? The 20 minutes around the same temperature, everything else. Correct.
Dr Cas Fuchs: Exactly. Even the same participants. So it's kind of an extension on the acute, uh, study.
We did it together. Yeah.
Dr Mike T Nelson: And with the D two model, which I'm not super familiar with, what, what can you tell us from that? Is that actually looking at like changes in lean body mass or amino acid content, or what is the, I know the advantage of that, if I remember correctly, is it allows you to do kind of more longer duration type things, but what do you actually learn from that method?
Dr Cas Fuchs: Yeah. So in short, why it's beneficial is if we now look at the infusion techniques that we do. So just to make it simple, we infuse labeled amino acids and then over like some hours after, we can measure and calculate protein [00:14:00] synthesis. That's is of course great if you have people in the lab that we have them here internally.
Uh, but if you wanna say a bit more about longer term changes, let's say a couple of days or maybe a few weeks. Of course you cannot have people here on an infusion line, always in a lab. And then we can use this technique deto. Oh. So it's basically labeled water. And of course we all drink water every day and get it from in our bodies for our foods.
Uh, but this labeled water is, is a very cool technique because if you ingested it kind of will be used by everything in our body essentially. And it's also very stable in the way that it is being used to produce amine, which is an amino acid. And that amino acid we can, uh, see in our muscle if we.
For example, take a biopsy. And with that we can then actually do the same thing by calculating muscle protein synthesis by seeing how much of the labeled lumin is being incorporated into muscle protein.
Dr Mike T Nelson: Very cool.
Dr Cas Fuchs: Very simplified.
Dr Mike T Nelson: And yeah. Was, was there any [00:15:00] estimations you could do off of that short two weeks study to see any change in muscle mass?
Or is the study just very short and you can't really put a, so one of the hard parts I've had, 'cause one of the, I'd say at the top level practical question is, okay, so let's say I'm doing per most of the protocols, I'm going 20 minutes. I'm doing it immediately after training. I'm doing, you know, eight degrees centigrade.
I'm doing all the things that have been relatively well studied, that we have great data from your lab and others showing muscle protein, synthesis changes, all these things. If I do that every day after training at the end of a month, how much muscle is that costing me? Right. Is it costing me a quarter pound, half a pound, a pound?
And I've had a very hard time giving any estimate based on the research because there's different techniques. Like some of the changes you'll see like cross-sectional fiber surface area, CSA changes, but it's hard to scale that up to an actual human. [00:16:00] Even MRI is is sometimes hard to extrapolate because the average Jim, bro, that's usually the typical question, you know, is it costing me?
Yeah. Typical, you know, like, and I dunno, I dunno if you have any estimate on that. And I've, I've had a very hard time coming up with. Anything.
Dr Cas Fuchs: Yeah, no, that makes sense. So just in short, of course, protein synthesis for people. Okay. Many people have heard of it, but indeed it's not like really something that you can like see or you know.
Right. What I can say there, we found about 20 to 25% difference, which is a lot. That's su ob acute five hours. Yeah. The two weeks we found 12%. It's still a lot, if you think about it. Sure. But to make it very practical, I think then it's great to, to get back to that study from, um, from Australia, uh, from Liam Roberts, where they actually found that, if you look at quadriceps muscle mass I, I'm, I think I have the numbers correct, but they did.
They focus on the quarry eps. And while people know the [00:17:00] quarry eps and 12 weeks of resistance training, I believe they found in the control condition where they did active recovery after exercise. I think it was just like cycling itself, selected intensity. Uh, but they found 300 grams of gain. Uh, that's about a big stake, at least in Netherlands.
I'm not sure how it's in the, you know, well be in the states, but it depends on where you go, where if it's steak out or not, but like a big, let's say big piece of beef. Uh, if you look at the group that did the cold water immersion, it was only a hundred grams. So you still gain, of course, because you have, you do resistance exercise, you do progressive training, uh, but it's about 200 grams less.
So that's also here, if I go to the supermarkets about, I like a, like a stake and it's a stake. And I'm only talking here about your quad receptors. I have to check. But that's, I think, I think a great paper to, to look into if you really wanna have like some practical, um, more like. Takeaway from it.
Uh, but that's what they found. And that's definitely very substantial [00:18:00] and certainly if you want to gain mass for bodybuilding releases or whatever.
Dr Mike T Nelson: Yeah, no, no, that's awesome. I have to go back and review that, that paper again. So that's super, super helpful.
Dr Cas Fuchs: Yeah.
Dr Mike T Nelson: Um,
Dr Cas Fuchs: some j physiology, so
Dr Mike T Nelson: cool.
Awesome. And also I just wanted to highlight, we had, uh, Jean Rolan on here talking about a similar technique he used with the a hundred gram bolus. And obviously Dr. Van Loon is the one who came up with this technique. And to me it was super fascinating because like the stable isotope stuff I find just utterly fascinating, but it, it's hard to extrapolate that per se to the, the average gym goer where I think if you explain to them that.
You know, hey, we put this cool label in your protein and we track that protein of where it goes into the muscle. Again, this is highly overly simplified. Um, but it, I think it allows you with a fair amount of estimates to get at the number the average Jim Bro wants, [00:19:00] right? Of a, if I did this thing, like literally how many more grams of muscle tissue am I gonna have or not.
Again, this is a very hypertrophy, centered discussion. And I also found it hilarious that some of the, the comments early on were, oh, well, why didn't you use casing that night? We all knew, or Why did you use, uh, casing to not weigh? Because they're like, oh, well you read all the bodybuilding stuff, it says casings a slow release, and then you talk to him and he is like.
No, it was just economics. Like if we did this with way, which I think they, you might have done at one point, now the cost would've been astronomical already. I think the first study they ran, he said it was like the most expensive protein like ever made. 'cause it took, had to get your own cow and they had to, get the feed and it took like, what, two and a half years or something to even get the technique to be able to be used in a study.
Dr Cas Fuchs: Yeah, I think that's what you say now. Like people often don't realize and it makes sense that they don't, which is also, of course you can't. Oh, of course. Yeah. They don't realize what's [00:20:00] happening in other jobs, but they don't realize what's happening behind, like a paper that they see and they often just read the abstract from and try to get some advice, but it's so much work and so much money and so much also pain oftentimes to get stuff done.
But it's actually good that you say that, uh, that Jorn, uh, already explained the cow because that's exactly this, uh, where we got the protein from that we also use in the cold water experiment. Yeah.
Dr Mike T Nelson: No, I just always love highlighting that because the pushback you always hear is that, oh, science takes forever.
But I think people don't realize the amount of work that goes in, you know, just to try to get that, just that technique and then now, okay, now you have the technique. Like you haven't even started your darn study yet. Exactly. So now you gotta run the study. Exactly. To use the, the technique and it just takes a long time in a very slow like stepwise fashion.
Dr Cas Fuchs: Yeah, absolutely.
Dr Mike T Nelson: Yeah. Yeah. Any thoughts? I know we hear this like [00:21:00] mythical, like, oh, if you wait the magical five hours, then this doesn't really matter. I haven't seen any studies that have looked at timing yet, and I understand why. Right? Like so. Like you mentioned, if you're looking at a new mechanism, you're probably gonna take a very high stimulus to see does this thing do anything at all?
Exactly. Because if it doesn't, one, it's, it's boring and journals don't like boring stuff. And then you was it, you know, four years of your life to find something and then the peer review will come back and say, oh, you numb nuts. You used five minutes of cold water. Why didn't you use 20 minutes? Or some big stimulus.
And then you do that study and then everyone online is like, why'd you do 20 minutes? Right. Right. But you, you wanna see, like if it didn't move the needle at some high stimulus, then you're like, eh, we could try something else, but maybe there's not something here that we thought. Any thoughts on a window of time if you were to speculate?
Like, if I wait X many hours or anything in that area?
Dr Cas Fuchs: Mm-hmm. I can, as [00:22:00] you said, like by my knowledge, no studies, definitely not on protein synthesis.
Dr Mike T Nelson: I haven't seen
Dr Cas Fuchs: any yet. Uh, no. I always tell people because it's only speculation that we can do, but what I do know, yeah, if, if you have a strong cooling, cooling protocol, and by that I mean for example, you go into water for like.
10, 10 plus minutes. I think that even if you, let's say wait for five hours, you still have some, I call it negative effect. The reason why I say that, why I think that is that of course in your, if you do a resistance training session, uh, we know that the anabolic window, and least like that window by which your muscle is still sensitive to amino acids from the meals and still working on like, uh, uh, stim or stimulating protein synthesis, uh, by simply then reducing the muscle temperature.
And also if you have Eden in that period as well, uh, the, uh, the vasoconstriction. So you kind of impairing the delivery of those amino acids to the muscle. It's still gonna have like some [00:23:00] negative effect to that. I think at least physiologically. That makes sense. So it's possible that it's not necessarily the same.
Let's say atten, attenuated response or impairment in response. But I still think it's not gonna be beneficial. But having said that, I think a lot of people do, for example, cold showers and they get their cooling from those kind of strategies. There, I would not expect much differences as that's like, of course, you know, just some water droplets, which are maybe cold, but it's not the same as like being in, in cold water for like a specific, uh, like 10 plus minutes of time, for example.
Uh, so it depends on the stimulus, but still, if it's a strong cooling stimulus, even if you do it later, I still at least think it's not gonna be beneficial to you from this perspective. Again, I always have to be careful because, you know, you could have maybe some other benefits, but, but not for protein synthesis.
So I still think if that's the goal, I would not recommend it for muscle mass gains and muscle strength gains, even if it's a bit later. [00:24:00]
Dr Mike T Nelson: Awesome. Do you think on the end of the spectrum, I know you mentioned some of the studies have compared it to warmer water can is warmer water or things that may increase perfusion, give us a bump more above baseline than just protein.
And related to that, I think there was a followup study, I can't remember, that came out this past year showing that it was most likely blood flow being impaired in the cold water immersion. That might be the main sort of mechanism of what's actually causing this drop in muscle protein synthesis.
Dr Cas Fuchs: Yeah. Yeah. So that's also study that we did here, uh, where we found a need that profusion was like definitely one of the reasons to see this impairment in response, again, which I made, which makes sense. And I think it's the perfusion as well as the temperature drop, that kind of together gives us, let's say, in, in, at least from this perspective, an unfavorable environment.
Um, so that's true. That's the mechanistic, uh, uh, part of it, uh, regarding your first point with halt water immersion, that [00:25:00] was, or, or follow up idea as well. Okay, cool. If, if cooling is not beneficial, what about if we heat up the muscle? Uh, so we did kind of very similar experiments, actually the same, but just we changed.
Uh, cooling one leg for 20 minutes into heating one leg for 20 minutes. And there we, um, we used the 46 degree cells, so very warm. I piloted myself and I was kind of the max, what I could get from, for one leg. Don't even do this for your whole body. But I, I used that approach and the study, and then we actually did not see any difference at all.
Hmm. So to me that's at least how I interpret the data that we found was that okay. It seems, and we know that if you do exercise, of course, you heat up your muscle already. Uh, you kind of see this big increase in, in blood flow towards the muscle, right. The muscle pump. Uh, it seems like that, that your body knows quite well, uh, what it needs to, to, to have this optimal environment for recovery.
And by having, let's say, a relatively short. [00:26:00] Heat exposure. This was, again, 20 minutes didn't really further seem to benefit, uh, the, the process of muscle protein synthesis stimulation. Uh, so it's still a question to me, what if you do it for maybe a longer period of time with a different heating modality?
But yeah, we didn't really see the, the increase in muscle protein sensor, if you would, let's say, take it practically if you would sit for 20 minutes in a jacuzzi following a resistance exercise training bout, but also it was not negative. So if people like it, I always tell, just go ahead and, and chill in the jacuzzi.
But don't expect necessarily to see gains in your muscle mass from that.
Dr Mike T Nelson: Awesome. And one of my pet peeves, and I don't know if you would agree with this online, is that. Everybody seems to say that cold water immersion is anti-inflammatory and it's the anti-inflammatory effect that's dropping muscle protein synthesis.
But when I've read most of your work and even some other earlier work that was done quite a while ago, all the [00:27:00] data I've ever seen, with the exception of this, some, a couple data from cryo, which is just cold air, not necessarily cold water immersion. Almost all of it shows that it's not anti-inflammatory, at least in healthy individuals.
I'm not talking pathologies. Would you agree with that or what is your take? Because I know you guys measured that directly.
Dr Cas Fuchs: Yeah, no, I, I do agree on that. Uh, that's what you always indeed see online. Uh, oh, it's because of inflammation, blah, blah, blah. Uh, there is some, quite some studies that looked into, uh, plasma markers of inflammatory mm-hmm.
Uh, markers in the blood. But we, and also, uh, also from Australia they, and we u try to measure inflammatory markers in the muscle. And, for example, we did mRNA expression. So I, I by no means say that that's giving you the whole picture, but at least gives some indication. Right. And we did not see any, let's say effect of cooling in terms of lowering that inflammatory response.
Uh, so to [00:28:00] me it's like, it's definitely not. That we can say with certainty that it's causing it because of the inflammatory response that people are always talking about. Um, I really go always back to, I think that the main mechanisms are the drop in the temperature of the muscle as well as the, uh, lower perfusion.
So the lower ability of the delivering the nutrients to your muscle cells. And yeah, maybe future research will, will give more insights into inflammation, but at this point I'm fully with you that I'm not convinced that we can say that there is the mechanism that we should look for.
Dr Mike T Nelson: Yeah. And you think the lower cooling is also, like you mentioned, changing maybe some enzymatic reactions that are also potentially having an effect then too?
Dr Cas Fuchs: Yeah. Exactly. So you mean like the, the enzymatic response for like, uh, mTOR signaling and, and those, correct.
Dr Mike T Nelson: Yes. Yeah, yeah,
Dr Cas Fuchs: Yeah. So I, I think that's indeed all like aligned with the fact if you, if you reduce your muscle temperature, you reduce all this anabolic [00:29:00] signaling. And this is one of the reasons, again, together with the, the lowered, uh, delivery in terms of by which we see this impairment in the muscle protein synthesis.
Yeah.
Dr Mike T Nelson: Any thoughts on, and you may not have looked at this, but any thoughts on cold water immersion after aerobic training? Because I've seen some mechanistic data that, you know, may increase PGC one alpha in. Most of the data I've seen, my interpretation is it, mm, I put maybe be beneficial for aerobic work, but it doesn't seem to be as negative for that.
What are your thoughts? Yeah,
Dr Cas Fuchs: true. So if you look at acute signaling responses and if you focus for endurance more on PDC and alpha, uh, important for mitochondrial biogenesis or even vascular endothelial growth factor. So for capitalization, uh, there we see that acutely, there are quite some studies that show that this is upregulated so higher than if you would not do cooling.
So that [00:30:00] gives some insight that maybe indeed you are able to make more mitochondria or maybe more capillaries, which is indeed beneficial for an e endurance athlete. But if you look into like longer term studies indeed with. So, for example, if I go back to the resistance training study, we see clearly like a re uh, like reduced gains in muscle mass and strength.
But for endurance we don't really see much differences. So it's not necessarily negative, not necessarily positive there. From an adaptation perspective I would still love to see data and, and maybe if there's money at some point in the future to to measure mitochondrial protein synthesis, following endurance bandwidth with this technique, that would be great, uh, to get more insights into that.
But yeah, as you say, like acutely there is some, okay, maybe it's has some benefits even, but in the longer term so far, there's not like clear evidence to show that it's, uh, giving you. Benefits following, uh, repeated endurance exercise bouts [00:31:00] maybe on recovery as well. Then, uh, Mike, so, so this is more the adaptation side.
We also, of course, for endurance athletes always focus a lot on glycogen. Uh, definitely if you have back-to-back competitions like Tour de France, for example, by which you need, uh, enough glycogen in the muscle to, to support your exercise sessions or your races. Um, there we see that if you do a very strong cooling protocol, uh, then you actually see also this impairment in, in the repletion of muscle protein synthesis.
So you see lower increases in muscle protein synthesis compared to if you would not do this. Intense cooling protocol. Having said that, there is also data from the uk from Liverpool where they actually did only 10 minutes of water immersion for I believe 10 degrees cel. That was, I think was eight degrees Celsius for 10 minutes.
They did not, not see any, any, any changes. Hmm. So I think even there as well, there is like if you have a strong cooling protocol there, you could even also impair your rec acute recovery process of [00:32:00] specifically focusing on the muscle glycogen synthesis. Uh, so even there, it's also like you have to be a bit cautious about what's the goal of my endurance bouts and should I apply it or not?
Dr Mike T Nelson: Yeah. Awesome. And related to that, I've, I've seen some data on more, I guess I would've been in a more neuromuscular function that some of the data shows performance might be increased. Some of the data shows it doesn't increase, some of the data shows it gets worse. It seems to be a, just an absolute mix of whatever.
I just wonder, I was talking to someone the other day about this too, like how, how much the placebo effect and no SIBO effect affects this. Like, 'cause you talk to some athletes and they're like, man, I love doing cold water immersion. Like, I swear it's the greatest thing I've ever done for my, you know, recovery next athlete's.
Like, that's the stupidest thing I've ever done. I hate it. My coach makes me do it. It's dumb. Like, I [00:33:00] would love to see a study that used cold water immersion and literally just split 'em into like the placebo group who loved doing cold water immersion and the no cevo group who just absolutely hate doing cold water immersion.
And see if there's any difference between those two groups. I, my guess is I think there's a big difference, but again, I, I can't point to any studies on that.
Dr Cas Fuchs: So when you started, uh, talking about this, basically you give exactly the same kind. And so I would've given you that. So it's funny about, so what we, we do a practical as well.
And quite some years ago there was at least, let's say, it kind of shifted over the years somewhat with, with people not believing as much anymore, at least the students here, maybe because of what, you know, yeah. What they got taught here at the uni. Uh, but believing in cooling as a recovery strategy.
And also now if you look at like some, uh, some measurements on the bios by which, which we measure, uh, MVCs. So let's say [00:34:00] maximum muscle strength, we don't really see much, much differences anymore. I'm not saying that we saw big differences in the past, but it seems to be also if we ask people not, I said, nah, I don't think it does much.
And also my muscle, uh, my muscle soreness was not really changing the, uh, between like either cooling or no cooling and definitely this, this placebo effect. And there are studies showing that there is indeed a placebo effect on this recovery strategy. Yeah. Uh, but I think that plays a big role as well.
Um, and yeah, you're right. Also, I'm, I, I quite puzzled by all the studies that looked into cooling following exercise and some find benefits, some do not find benefits in terms of, of acute muscle performance. So yeah, even there are a lot of questions that we still, uh, could answer and could dive into, but yeah, I think such studies would be interesting to, to do.
Dr Mike T Nelson: Yeah, and I think even on the body count, if I remember correct, I think Dr. Greg half did one, I wanna say it was in soccer players and if I remember right, I think [00:35:00] they had a a cooling arm and a warming arm. And I don't remember that they saw much difference in lean body mass or fat loss or if I remember right, they didn't see much of any difference in it.
Like in terms of body comp. Yeah. I don't know if you are familiar with that study.
Dr Cas Fuchs: Yeah, yeah, yeah. I think it's also what shown s on that one, I think it was in elite rugby basketball players. Oh, maybe that's what it was.
Dr Mike T Nelson: It was in pretty high level athletes. I remember that.
Dr Cas Fuchs: I also think it was 50 minutes of either hot water immersion or, or cold water immersion or a control condition.
And they used DEXA scanning and looked at whole body. Yes. Uh, total whole body lean mass. And indeed they didn't really see much differences. That's actually one article I always, um, highlight as well, if I give this, if I talk to this student, master's students here and said, okay, there is like, you know, in the longer term 12 weeks, we see like some impairments.
If your main goal is, is, uh, gains in muscle mass, but you know, if you do it a few, like for let's say a shorter period in your overall training program by which you also do other [00:36:00] types of training sessions, you know, it's not something that you have to be like if you have sitting like a water bath for once and think, oh damn, now I have to ruined everything for the next.
It's kind of definitely more context specific. And I think that study at least for me, shows that nicely, uh, would be, yeah, would, would be interesting. Also, that was with DEXA scan. I would be, I would love to see what happens in the muscle. Because you cannot really measure that with Dexa, but still gives, gives an interesting indication on that.
Yeah.
Dr Mike T Nelson: Yeah, that was my thought too. Like if you did that exact same study and you did MRI or something that's a little bit more in in depth than Dexa and DEXA is good, but something that has a little bit finer limits a difference, like would you see a difference? I don't know, on some days I'm like, yes.
And other days I'm like, I don't know.
Dr Cas Fuchs: Yeah, no, exactly. I actually did also comparisons on like, uh, d and MRI scanning. And it really also needs, if you, if you look for example, at like, tissue [00:37:00] atrophy, uh, we found that if you have people very well standardized for two weeks in a bat, we know you lose a lot of muscle mass.
But we can actually also measure it with, with a DEXA scan, like a very similar decline in, in, in, in that, that sense than likely mass. Uh, so indeed it, it's, it's definitely a useful technique. And it's depending on the question and how precise, maybe you need to have answers of what you want to measure, if you can apply it or not.
But it definitely gives some interesting insights. Yeah. Yeah. And then much, much more easy to do than an MR MRI scan.
Dr Mike T Nelson: Oh, by far. And way cheaper. Not the dex is cheap, but compared to an MRI, it's cheap.
Dr Cas Fuchs: It's very cheap. Yeah. Yeah,
Dr Mike T Nelson: yeah. And again, you could argue with that study that. There wasn't this, this huge, massive difference.
And Dexa is good enough for, you know, what the question you're, you're trying to answer. So
Dr Cas Fuchs: Yeah. No, absolutely, definitely is is a very interesting insight from that study that we can, uh, take away. Yeah.
Dr Mike T Nelson: And do you think cold water immersion is magical [00:38:00] for fat loss?
Dr Cas Fuchs: No. No, no. That's, that's also sometimes that I've heard people talking about, uh, no, I, what, what, what did they even say?
I actually forgot was maybe with the, with the cold shock response or something that everything gets activated and all of that stuff. No, I, I don't see how the only thing, maybe it could have like a very small effect. Uh, if you, if you put people in like maybe, uh, cold suits or something by which they shiver.
Mm-hmm. Right? They have all these contractions. Yeah. And therefore you expand something. But if you compare the people like that actually do like. I would now call it the optimal way of fat loss. So watch your diet carefully and not together with exercise then. I think it's very minor. And I don't expect, this is definitely not a magical way to to lose fat.
Definitely. You have to first of all look into your diet and eat less than, than what you would expect on a daily basis for a prolong period of time to get, uh, to see what's happening or to, to actually lose fat. [00:39:00]
Dr Mike T Nelson: Yeah, that, that's what I got from the literature too. 'cause I initially started pulling all this years ago and my first thought was, I'm like, I was cautiously optimistic.
I'm like, okay, like if you do the physics and you do the thermodynamics, like, uh, it might kind of work out and then you start looking at all the research and basically no, like the only study I could find is the one you referred to as super old study maybe 50, 60 years ago from the military where. They stuck people in a pair of shorts, like literally in a, a freezer, and they left them in there for I don't know how long it was, hours, and they were just sitting there, just shivering.
And they did see some fat loss in that study, but no one's gonna do that. That is absolutely horrible. Nor would I recommend anybody do that. I mean,
Dr Cas Fuchs: you know, if, maybe, I haven't really thought about this now, but if you have people that for some reason cannot do exercise and they still need to lose some, some, [00:40:00] some body fat, then, then maybe like some such extreme strategies could help something.
But again, if you look at the norm, the, the healthy person that can do like, you know, watch, watch their diet and do exercise, then it's very minor at best, I would say. Yeah.
Dr Mike T Nelson: Yeah. And if anyone's done enough cold water immersion to get to the point where your teeth are chattering and shivering uncontrollably, which again, I would not recommend anybody do this.
I may have tested that in my garage freezer full of water. It is miserable. Not only is it potentially bad for your health, like you feel miserable for hours after, like you just cannot physically get warm. Like you can't focus on anything. It, even if that was a thing that ripped fat off my body, I still don't think I would do it.
Dr Cas Fuchs: Yeah, no, that's another thing. Yeah. Yeah.
Dr Mike T Nelson: Awesome. Any the other thoughts on cold water immersion or stuff you see going around that you wanted to comment [00:41:00] on?
Dr Cas Fuchs: So yeah, I think what I still find interesting is to, what I already mentioned, look more at maybe at the endurance, uh, side of things. Mm-hmm. So if there are benefits there that's still some questions that I have.
I think for resistance training, I mean, you know, we are scientists, we're always interested to get more data on like similar topics. Uh, but to me it's, it shows quite nicely that lines up that, that it's not, not going to give you the benefits of gaining muscle mass. So, but like for the endurance part of.
Side of things, I'm, I'm still interested in, in some questions that I would like to be seen answered. Um, and then maybe not so much the cooling or because cooling, you can also think about other thread, like the cryo saunas, the cryo chambers. That's like very popular now. And a lot of sports teams that have a lot of money, they have these, uh, um, things installed at their facilities.
Um, but I think heating is also something I'm, I'm still very interested in to see like, Hey, what happens with sauna? What happens with, if you go actually for, uh, in hot [00:42:00] water, do hot water immersion, go into a jacuzzi, uh, or even these devices by which you can do very localized heating, which is, uh, something you can do with diathermy, for example.
Mm-hmm. I still think there is quite some, some interest in seeing like, Hey, how does, what's happening with these strategies in terms of muscle physiology, what is changing or not? And maybe how could we use such tools to, to improve yeah, muscle, muscle mass or muscle strength or just general health in general.
That's, those are still, I think, quite some questions that are, that can still be answered. And that's more, maybe not so much just the cooling, but just cooling and heating or just temperature in general. Still very interesting to me.
Dr Mike T Nelson: Yeah. The one thing I've done, which I call like poor men's contrast therapy, if you only have cold water immersion, you live in a hot environment is, and this is more of a eustress model.
So I'll drag my rower out in the middle of the street, do a bunch of rowing on that, uh, especially on hot temperature days. And then I'll get in the cold water immersion for maybe one or two minutes [00:43:00] dry off. And then I'll go back and do the rower again. So I'll go do intervals back and forth. And what I found was the cold water immersion to basically.
Dump all the heat that I generated. My performance on the following intervals was actually quite a bit better. I don't do it a lot because in all honesty, like it sounds stupid, but like toweling all the way off and putting all your clothes back on, it just gets to be kind of a pain in the ass to do.
But the handful of times I did it, I, it was quite interesting of how much of a difference that made and that kinda makes sense. Looking at the literature that, you know, if you can't dump heat, that is probably gonna be a limit to your exercise performance. I don't think there's gonna be any benefit to that if you're in a thermal neutral or probably not a hot environment.
Dr Cas Fuchs: Now if you can get rid of the heat from your environment, indeed you're right. But exactly. If it's already very warm and also humid outside and you even like with sweating and the evaporation from much of difficulties to get rid of the heat, then [00:44:00] that could indeed be like, or a cooling vest you see people applying sometimes, you know, uh, or like even have these gloves that you see, something that people put like, uh, cold
Dr Mike T Nelson: Yeah.
Dr Cas Fuchs: Water around to kind of get like help your body to get rid of, of body heat and therefore still be able to perform for longer in like warm environments. Yeah.
Dr Mike T Nelson: Any thoughts on that? Cool. Mint? Like I've seen, I've tracked that thing for God. I first saw an article on it 14 years ago, I think in Wired magazine, and they were saying like, oh my God, my endurance went crazy.
And then I checked on it and someone did file a patent and then someone else sold the patent. I think the university had the patent for a while and now supposedly somebody else has the patent and. It's basically cooling device under vacuum through the hand. And they claim that even at like thermal neutral type environments, that because muscle activation requires heat, that if you can cool it, that the heat dissipation will make a big difference in [00:45:00] performance.
But I, I can't find hardly any literature that's been reviewed. I can't find anyone who's used it and tested it. It just seems like this mythical thing that keeps showing up every few years with these crazy claims that I can't. Verify. I want it to be true, but I, I don't know any thoughts.
Dr Cas Fuchs: Yeah, I actually, I'm not a hundred percent sure if this is related to the cooling glove, but I even once read this also a long, a long time ago that there was even like, maybe it wasn't even like a news article based on a scientific article, and it was even in the discussion of the article, but they said like that the, uh, the gains that you could make by your exercise were like the same as using anabolic steroids.
Yeah. In terms of like doing pullups or something, if I recall. Yeah, it was pullups is what they used. Yeah,
Dr Mike T Nelson: yeah, yeah.
Dr Cas Fuchs: I'm like, yeah, you can, you can't make that this, but you know, I mean, if you, if you are able to, to help your body by. By getting rid [00:46:00] of heat in a warm, humid environment. Uh, yeah. Then maybe you could do some more pull-ups.
That, that, that didn't to me make some sense, at least if you do it for, you know, more prolonged types of exercise sessions. Uh, but is it more like beneficial than than other ways of cooling? I'm not Maybe. Depending on the type of activity you do, like you go, of course, if you, if you, yeah. Now you can go into so many different topics, but for example, sprinting, you don't want to go into, like cooling your legs off because you know, you need warm legs to be able to sprint and it's not even like a limit limitation, uh, necessarily like the heat that you build for a very short period of time.
So, yeah, I think it's, it's also something I, I, I re I recall, I haven't looked into this for a long time. I'm very interested in it and I think water or like hand cooling can have a place as a way of a cooling strategy. But being it's something magical, um, doubtful.
Dr Mike T Nelson: Or, uh, I'll tell [00:47:00] this is about one or two years ago my buddy coach Cal Dietz had, uh, cold, uh, soda cans.
He was testing with his athletes as a way of dissipating heat. So I took my freezer with a cold water immersion and may have put cans of soda in there. And in the summer to use that to just basically hold 'em in between sets to see if I noticed a difference. I thought, I don't know, maybe this is like the $2 version of a thousand dollars device.
It seemed to help, but I, I, I couldn't notice like a huge difference. And then, you know, the people who sell the device would argue that, well, because it's not in a vacuum, you've got local vasoconstriction and you're not really getting the heat dissipation that you want would be their argument. I don't know.
I guess if people want to try it, that's like a $2 way they could try something and let us know if there's any difference.
Dr Cas Fuchs: No, and, and even like, um, putting like a, like a hand in, in, in cold water for a longer period of time. Mm-hmm. I have heard people and also that it could [00:48:00] maybe be beneficial again in some settings, but Yeah, like to, to call something magical.
I'm like, uh, always skeptical.
Dr Mike T Nelson: Yeah. But
Dr Cas Fuchs: yeah,
Dr Mike T Nelson: and if you, you also have a pain response too of, you know, sticking your hands in cold water and that can definitely inhibit performance too, so that, you know, it could go both directions depending upon, I could, I could give you some physiologic mechanism of how it's the worst thing to do for your performance.
I could give you a mechanism, but it's the best thing to do. And yeah, it's probably new neither. Yeah. Cool. Last question on the cold water stuff. I appreciate all of this. It's super interesting. Any thoughts about doing it before exercise? It seems like that's sort of the new trend. And I, I talked to, uh, Dr.
Tom from Morasco Forge, uh, about this too. And you know, he cited some older literature that there's these increases in testosterone if you're doing it before exercise. And we do know there is increases in epinephrine, norepinephrine, and dopamine. There's one study that's been published on that, whether that shows up chronically over time [00:49:00] is probably up for debate.
Mm-hmm. And obviously you'd wanna warm back up so you're not going into exercise completely cold because we know that can affect performance. But any thoughts about doing it before, like a lifting exercise?
Dr Cas Fuchs: Yeah, I think again, indeed, you don't want to have your muscles necessarily cold. Right. So, but having said that, uh, if the environments you're doing, you're exercising is very warm and let's see, also humid, so more like the extreme conditions by which it's difficult for your body to get rid of the heat.
And then there are some studies that nicely show that if you do pre-cooling, that it can help you performing.
Dr Mike T Nelson: Yep.
Dr Cas Fuchs: But again, it depends on the type of activity. If you do a sprint, it's not really, you don't wanna cool your body, uh, and certainly not your leg muscles. Uh, so then I would say don't do it.
And even there are studies by my knowledge, that actually showed that there was also impairments in, in that performance. But if you, let's say, okay, I'm gonna go for like a five hour ride on the bike, uh, as an example, [00:50:00] and it's, you know, it's very warm outside, you also see like. Athletes, um, you know, having cooling vests or like, do some kind of pre-cooling measurements in those situations, it could make sense to, to improve that performance or at least start off your body not already too warm by which you, IM impair your performance quicker during exercise, uh, for weightlifting.
Um, yeah, I mean, I think it also depends on where you're doing it. I think in the USA, you guys have some beautiful beaches where you can, uh, do, do weightlifting. If it's warm there, then maybe you could even have some benefits. But then, you know, the gym's, the gym that I go to, like your, your inside there's is air conditioned no benefit of, of pre-cooling on that.
So I think it's really dependent on what's the limiting factor and if that's becoming that your body cannot get rid of the heat, uh, then there are settings or situations by which, and context by which I think it could have some benefits. Yeah. But not always.
Dr Mike T Nelson: Cool. Awesome. Uh, we transition a little bit [00:51:00] into different things related to, uh, glycogen resynthesis, and I know you've done a lot of work on that.
I mean, no temperature can affect these. Correct. You had mentioned that if you're staying cold, that's gonna affect how well your body can basically stuff these carbohydrates back into muscle. And I assume that's probably just due to enzymatic changes again, because of the colder temperature.
Dr Cas Fuchs: Yeah. And, and also the delivery again of the, uh, carbohydrates.
Dr Mike T Nelson: The blood flow's gonna be less too, so your perfusions gonna be lower.
Dr Cas Fuchs: Yeah, exactly.
Dr Mike T Nelson: And you also talked about using different types of carbohydrates, uh, I think using like fructose and some other forms. Yeah. Do you wanna explain a little bit of the theory behind that? And there's been a couple of very cool studies on that, that have shown that to be beneficial.
Dr Cas Fuchs: Yeah, sure. So that was actually one of the first studies that I've, that I was doing. So just, um, again, if we go to glycogen repletion following exercise, and this [00:52:00] is of course can be relevant for all, all athletes, intermittent, even sometimes resistance depending on your training program, et cetera. But it's mostly used and really focused on for endurance athletes.
Again, to put it in context, things like Tour de France, they have a very limited recovery time between two, uh, two races, two stage races, and they wanna really increase glycogen, repletion as quick as possible and the muscle, and actually also in the liver. 'cause the liver supplies your muscle during exercise with carbohydrates, by breaking down the glyco stored locally in the liver will be transported to the muscle.
And then what we did is we wanted to know, okay, what if we look at different types of carbohydrates that we give following exercise? And we not only measure the muscle because muscle, uh, since, um, the sixties, and then a lot of Scandinavian researchers and a lot of people now from all over the world who will take a lot of muscle biopsy, including in our lab, uh, to measure muscle, muscle glycogen, uh, but with, with nice techniques.
We can also measure in [00:53:00] the liver. We know the liver is important. And again, we wanted to combine those two together. And what we did, we, we provided participants or cyclists following a depleting bout of exercise on the bike. We provided them with either glucose or with sucrose. And sucrose is basically 50 50 of glucose and fructose.
So those are two different monosaccharides. And the id, why we wanted to test those two was that from like decades ago, we have like mostly focused on, uh, providing glucose or glucose polymers in recovery or during exercise. And over the last, yeah, already quite some years now, but there is more focus on like looking into different types of carbohydrates such as glucose and fructose.
And this fructose component is interesting because it's really used and, and metabolized predominantly in, in the, in the liver. We wanted to know if you provide both of those, so glucose and fructose, is that better for liver glyc [00:54:00] pleasing compared to just glucose? So we did that study five hour recovery period, and I talked a lot now already, Mike, I'm sorry, but, uh, you're good.
Five hour, five hour recovery period. And then providing in that study, 1.5 gram per kilogram body mass per hour of either glucose or sucrose. And we found that for muscle it didn't matter. So you saw the increasing glycogen resynthesis as you would expect because you give the, uh, substrates to be used to, to build lyin there.
Uh, but for the liver, we saw big change. It was almost doubling. So by having more fructose in your, in your post-exercise meals, you kind of can support your liver more than if you would say. Or predominantly stick to glucose based meals. Um, so that was the first study by which clearly we showed that, that was beneficial for the liver.
And there's actually studies before that that showed the same thing, uh, but that they only measured the liver. So we now measured muscle and liver and now we found, okay, muscle doesn't matter, liver. It does. [00:55:00] So if you look at overall total body gly, repletion, it would be great to add some fructose in your diet.
And that was kind of the first, and, and now I'm like also doing more studies on like, um. Looking at how quickly can deliver replenish. A recent article published, uh, we also provided, uh, sucrose over the first six hours. And we actually also then measured the whole 12 hour period, uh, in terms of muscle and repletion.
And we kind of found in that study, and maybe just again to tell the, explain the design a little bit. So we, we scanned people before and after a, a bleeding bout of, or like an exhaustive bout of exercise on the bike. And I say scan because with scan we can non-invasively measure gly and liver and the muscle.
And then afterwards we looked for 12 hours. At six hours and 12 hours we scanned them again. And we either gave them absolutely nothing. So that was, uh, the remaining facet for like a long period of time. Or we provided like, uh, the [00:56:00] first six hour sucrose based drinks and then the last. Six hour window.
We provided two carbohydrate rich meals to make it a bit more practical. And we actually found that muscle was, uh, in those, let's say, optimal carbohydrates conditions, uh, not replenished within 12 hours. Not very surprising because previous studies have shown you probably need around 24 hours for that.
Uh, but the liver was already like above baseline, so before the cycling within six hours. So again, showing that if you give sucrose, uh, we didn't compare it to glucose there, but if you give sucrose or you give a mix of glucose, a fructose, that it's really beneficial to give. I have like a big stimulus on stimulating glyc repletion in your liver.
And again, to make it practical in the long term you want, in those settings, you want to have high glycine availability in muscle and in liver. So that's very beneficial to focus on different types of carbohydrates.
Dr Mike T Nelson: Oh, that's cool. [00:57:00] And this would be obviously super important for people doing back-to-back exercise or they're doing extremely intense demanding exercise one day and they gotta come back and do it again the next day.
Correct.
Dr Cas Fuchs: Exactly. So if you have to train twice a day or you, let's say, okay, tomorrow is an important match, and then the day after again, then it's really important if you say, I'm gonna do a marathon run, uh, marathon and like for the week after, I'm like, more, yeah. Not maybe some, let's say, um, low intensity training session, but nothing important then it's less of a, less of a, um, yeah.
Less relevant to focus really on those different types of carbs. So you can just have like some, some good meals with enough carbohydrates to restore it. Uh, but for indeed, the back to back, um, sessions is very important.
Dr Mike T Nelson: What are your thoughts about that seems to be any. Uh, I'd say more elite endurance world.
This pushing of how many grams of [00:58:00] carbohydrates can we get in per hour during exercise? It seems to be like this escalation war of, it used to be like, ah, you know, 60, you know, and then, ah, no, we, we went over a hundred and now it's like one 50. And it seems like every time I turn around, someone else is claiming that they're at like, the next highest number.
Dr Cas Fuchs: Yeah, yeah. Yeah. It seems to be a thing now. Yeah. Yeah. That's actually, that's actually interesting because it relates also to the fructose, what I said, it's like,
Dr Mike T Nelson: right
Dr Cas Fuchs: as you say, like in a days it was always like the max was 60 gram per hour during exercise, and that was of glucose. Uh, because if you give higher amounts, we, we didn't measure a day because back then I wasn't even in science, I wasn't even old enough.
Uh, but they, they found that you know, you can give more glucose, but it didn't. Didn't benefit you because you didn't oxidize, so you didn't use it. But then, and this is a nice work from, you can rep, uh, back then, uh, he was also a matric doing a PhD in the past. Uh, but they kind of figured out like, Hey, if we [00:59:00] combine glucose with fructose, you can actually increase that amount that you can oxidize during exercise.
And then they, it led to like, oh, we could actually go to 90 gram per hour. If you mix, of course, then it's still important to look at the, if you need it during exercise, depending on the intensity, the duration, et cetera. So that was prolonged, like the, the advice, if it's like a longer intensity or like higher intensity per longer duration go for 90 gram per hour.
Now there are studies showing that 120 grams per hour could even lead to a bit higher or actually quite some higher oxidation rates. Uh, the question still is, is that going to benefit your performance? They found like no further sparing on endogenous glycogen stores. So there's, that doesn't really seem to be the mechanism, but yes, you can oxidize more and as you said, like now in practice, they even go higher.
So, um, I also, uh, work, uh, with the team vma, Lisa Bike professional cycling team, and they are even going, uh, higher some of these riders. And, you know, [01:00:00] it's, it's a matter of like. Carefully seeing how do they respond, um, what do they say? And a lot of it now is like, you know, they, some of them just try to increase it.
And as you said, like I, I've read stories about triathletes that even go, I think even beyond 200 grams per hour. I'm like,
Dr Mike T Nelson: right. I was like,
Dr Cas Fuchs: what? Could you, how, how, how, and if so, is it gonna benefit? Can you tolerate more or can you actually use more? I am, yeah. Let's say I'm at, I'm, I'm, I'm a bit skeptical on these high numbers.
I'm definitely open-minded because I think I sh we should be but we are definitely not there with science to say like, oh yeah, that makes complete sense and we need definitely more research to see if that's even going to benefit you or not. And then also, yeah, the, the, the placebo effect can play a role if you think, oh, I can actually ingest more and it feels good.
I'm, I'm performing better. I don't know. If it's really benefiting them physiologically or not, but definitely interesting to just to research [01:01:00] this more. And I think one more point that is important in practice is definitely if you think about, for example, tour of France, you can increase more and more during the race.
But it's really important that we figure out if we can use it as well because if it's just a matter of toleration and not using it, you kind of take away some room for like a recovery meal for example, which is also really important as we discussed about the glycogen that you want to re restore.
So there's a lot of factors that people have to, should take into account before just saying like, ah, let's just try to get us in as much as possible for trying, because it can actually be detrimental for other meals that you also want to use or need to use for, for other reasons like recovery.
Dr Mike T Nelson: Yeah, I mean, if you.
If you look at the data from even some of the testing that's been done with, uh, metabolic Cart, and you look and say, okay, even at high, high intensities, you're a hundred percent or close to a hundred percent, you know, carbohydrate oxidation, to me the numbers just don't add up [01:02:00] unless there's a bunch of freaks who just haven't been tested.
But you can kind of infer it based off of their power output as to theoretically about where they would be. And to me, like these 180, 200, like I don't, the math just doesn't add up to me unless there's some other central mechanism going on where you're, you're sensing carbohydrates coming in. So it's the whole, the nos, potential governor theory that maybe you've got a little bit less of that and your perception is like, I'm good to go even though my output isn't, and I don't know anymore.
Dr Cas Fuchs: No, I, I, I think we, we need the data, we, we should study or, and, and just see if it's for sure has benefits. And I fully agree on that. Yeah.
Dr Mike T Nelson: Awesome. As we wrap up, like what are some recent studies you've done or other studies you've got coming up that your stuff you're like super interested in?
Dr Cas Fuchs: So, yeah, actually like the last few days, so it's now impressed, but, uh, published an article now where we looked into, um, so it's now online, uh, where we looked into [01:03:00] breakfast and just look if, if the breakfast that, uh, in this case also well-trained cyclist.
How much of that would lead to more liver gtin?
Dr Mike T Nelson: Hmm.
Dr Cas Fuchs: Because of course, if we, we all, uh, like a well-known strategies, carbohydrate loading to kind of make sure your muscles are loaded and the day or days before, uh, leading up to exercise. But of course also people say, okay, then you have your overnight, if you do the day before you do loading, but then you have your overnight period by which your liver glycine is going to be reduced because of course you need to have energy for the brain and the cytes, et cetera, that require that that glucose.
Um, so liver glycine is reduced. And then the advice is always, okay, have a breakfast containing sufficient carbs to kind of top up that liver glycogen that you need to optimize than your subsequent performance. That makes sense. And there are studies showing that liver glycogen concentrations are increased.
We measure that as well. But what's interesting and what's fascinating to me is that if you [01:04:00] measure liver volume. Uh, in the morning and then in the early afternoon it actually reduces in size and we found that in this study as well. So yes, you see that over. Uh, and again, maybe just the design briefly, we give three grams of carbohydrate per kilogram body mass, and then we measured for three hours post ally.
So we wait for three hours and before and after we again took the scan to measure liver and muscle glycogen. And we found again, liver GTIN concentration increase, but the liver volume declines. And if you then look at the total storage, there was actually no change. So you don't really store necessarily more liver glycogen in, in, in grams.
Um, you, you do, and we didn't have a control condition there, but I do expect that you don't see the decline that you would otherwise see if you would remain fasted. Uh, but you kind of do not see the top-up that we always think happens because of that changes in [01:05:00] liver volume. And that seems to be very consistent.
Even if you eat that, you still, uh. Probably a circadian effect, but that your liver or your body decides that your liver, like during the day after you wake up, it actually reduces a bit in size and then it will come back up again. But that's kind of a fascinating thing that I, uh, I found, and that's actually quite interesting that we don't really see that the grams of glycogen in the liver are actually increased following a big breakfast with carbohydrates.
So that was something very recent. Now you asked me the question. Uh, and yeah, at the moment, a lot of things with the scan, I really like, uh, the, the MR scan because you can do great measures on on body composition, muscle mass and fat in different locations. So do research on that. Uh, also the research on bodybuilders to look at, uh, what happens to their muscle volume, uh, but also organ volumes, uh, that's not published yet.
And also now like doing more work with like, um, non-invasive waste. So again, with, [01:06:00] but then MRS, so magnetic resonance, not imaging, but spectroscopy to look more into, um, metabolites and changes with exercise with nutrition and all of these things. So a lot, uh, still a lot going on.
Dr Mike T Nelson: That's awesome.
Is there anything you can say that's public about the bodybuilder study or we just have to wait and read it once it's out?
Dr Cas Fuchs: That's hopefully won't take necessarily very long, but, uh, cool. I cannot share too much. Uh, I think from the muscle volume perspective, it's kind of expect expected, but some cool stuff on the organs.
But what we essentially did is we had like control conditions, so let's say recreation active meals that we took, natural bodybuilder and also bodybuilders using, uh, appearance and performance enhancing drugs. Uh, so amongst others anabolic steroids. And just look at what are the differences there when, when, when we scan them and do a lot of measurements on.
That's some, uh, some cool stuff that will come out as well. But I'll share it with you, Mike, as soon as, as I, as I, yeah,
Dr Mike T Nelson: no, that's great. Share
Dr Cas Fuchs: more
Dr Mike T Nelson: on that. That's [01:07:00] super interesting because they've had that one published study, uh, looking at, I think it was a case study on a single bodybuilder, maybe they had a couple that showed hyperplasia.
After many years of training and use of peds, which was I think one of the first times that hyperplasia had been demonstrated in humans, I don't wanna say conclusively, but at least in terms of a case report, which was pretty interesting.
Dr Cas Fuchs: Yeah. Even there, there's so much to learn and yeah, it's kind of, it makes complete sense, of course, but sometimes you think, ah, it'll be cool to do these and these studies and give, like, I know I'm certainly I'm certain that I can get a lot of guys interested in like, Hey, let's, let's give you some steroids for a prolonged period of time and measure you very carefully.
Yeah. Of course, ethical reasons, uh, restrict us in doing these things, so we are like stuck to people that are already doing it by themselves, which to some extent makes sense. But it's, it's interesting to dive more into what's happening there, uh, exactly. In the muscle cells and, and yeah, [01:08:00] a lot to learn still.
Dr Mike T Nelson: Yeah, I feel like a lot of those studies just haven't been done. I mean, what was it? Was it Bain? I think that did a lot of those in the nineties. Yeah.
Dr Cas Fuchs: Yeah,
Dr Mike T Nelson: he had a couple of studies and since then, like it's just been like, yeah, you can find stuff in health areas, you could find just kind of anecdotal stuff, but in terms of like, you know.
Hardcore meathead. There's just not much.
Dr Cas Fuchs: No, exactly. I think the, by my, uh, back in the days it was strict again, before I was there, they did some studies on, uh, on steroids. Also self-reported, but also they sometimes injected for like some weeks. And ever since I'm in the lab here with, with Luke, you already mentioned there was a study where we, uh, could inject a single bolus of Lon but that wasn't like issues because then, you know, yeah.
You can kind of more argue, it could be beneficial if people are injured or like lose a lot of muscle to kind of maybe see if we can help them. That was a, from let's say, I think for a lot of bodybuilders, a relatively low dose. But yeah, it, it's [01:09:00] very difficult. It's, you cannot really do many of these studies, uh, with like a lot of restrictions on that.
Yeah.
Dr Mike T Nelson: Yeah.
Dr Cas Fuchs: So we,
Dr Mike T Nelson: That's cool. Yeah, last question. If you were to give a rapid fire, like your top four things, the average gym goer should know about cold water immersion, what would you say?
Dr Cas Fuchs: So the guys that, or girls go to the gym, like for resistance training?
Dr Mike T Nelson: Mm-hmm. Yep.
Dr Cas Fuchs: Or just general? Um, for cold water immersion, I would maybe, let's say cooling, uh, if you really like cooling for specific reasons.
So people I know say like, could I take a cold shower? Yeah, of course you can take a cold shower. Uh, maybe it's some people report I dunno if this is, if, if there's solid backup for this at the moment, but they report sleep better. You know, by all means if, if you have ways by which you can sleep better.
We know sleep is so important for recovery, so to do it, uh, but then. If you say like, I wanna make gains for strength and mass [01:10:00] and I'm considering cold water immersion, like an intense protocol, I would say don't do it, uh, because it's not gonna help you from that perspective. Maybe if you go as, is it called Muscle Beach?
Is it right, Mike and, uh,
Dr Mike T Nelson: yeah. Yeah. Venice,
Dr Cas Fuchs: If it's very, if you wanna train there and it's very warm and humid outside, I dunno what the temperature's there, but I, I, I suspect it's warm there. Uh, then maybe before you could do like pre-cooling, uh, as a strategy. Uh, but like it's a bit context dependent.
I think mostly if you look at cold water emerging as opposed to exercise recovery strategy, I would say don't do it if your goal is to gain muscle mass and muscle strength,
Dr Mike T Nelson: awesome. Cool. Well, thank you so much for all your time. Where can people find out more about you if you want to be found outside of the lab?
Dr Cas Fuchs: Uh, I don't, no. Yeah, I, I share most of the work on my LinkedIn, uh, page these days. Sometimes still on, on x, formerly Twitter, uh, sometimes on Instagram as [01:11:00] well, but I, yeah, it's you know, Mike it's as a academic with also teaching a research is so busy that I, I am active on it, but let's say passively active, it's just sometimes you watch, it's not like that.
I'm a big, uh, social media guy. I do have the accounts. I do share my research so people can find me there. Just type in my name and you'll be, you'll be able to find me. Uh, and of course, if there will be specific questions, you can always email me as well. You can also find everything on the Mastery University website, uh, in terms of my email address, et cetera.
So I will be, uh, you can find me relatively easy. So that's the good news. I think. Uh, if you have even one to five.
Dr Mike T Nelson: Yeah, I always feel go back and forth, even asking researchers that question. 'cause part of me is like, I don't want to do anything if they're looking to get more exposure to hamper their exposure.
And then the other, like more sinister side of me is like, no, don't pester these people. They're doing like really cool research. Like, just let 'em do all the research.
Dr Cas Fuchs: No, and I, you know, [01:12:00] so I, I, I'll be honest, if people, sometimes people may ask like so much, they're like, yeah, it's not possible. But, you know, everyone can really ask, uh, ask questions all the time.
That's also, I think, what, what's cool about what we do. We love to share even what we did. Now, today we talked about research stuff we're fascinating about, fascinated about. So definitely ask questions. I'm always open to that. And maybe another reason, if you want to find me or Mike, you always ask Dave Church.
He, uh, he is like a, a good person to uh, to, to, uh, to contact as well. And he also has all my, uh, my contact details. So. Yep. Any questions
Dr Mike T Nelson: at all? Send them to dc.
Dr Cas Fuchs: Exactly.
Dr Mike T Nelson: Cool. Awesome. Well, thank you so much. I really appreciate all your time. This was great. Thank you so much.
Dr Cas Fuchs: Thank you for having me, Mike.
Speaker 2: Thank you so much for listening to the podcast. Huge. Thanks Dr. F for all of the amazing research he's done. Uh, I do reference a lot of it in the Physiologic Flexibility [01:13:00] Cert. Uh, that'll be open in probably around April-ish of this year. Um, really, really great stuff that he's done, um, in the lab over there at marick and just a wealth of great information and.
It's always wonderful to talk to the people who are doing the direct research and get all the info directly from them. So if you enjoyed this podcast, you'll enjoy my Daily Fitness Insider newsletter. Go to mike t nelson.com. You can hop onto the newsletter completely free. And we do have the Flex Diet Cert opening again February 9th through the 16th of 2026.
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But we do talk about a little bit of recovery. Neat [01:14:00] fasting, micronutrition. Some basic exercise and then of course, proteins, fats, carbohydrates, and much more. So hop onto the newsletter, mike t nelson.com and thank you so much for listening. We really appreciate it. If you can do us a favor by sending this to someone you think may enjoy the podcast do the all wonderful things of, give us some stars, drop a review, download, subscribe, all that great stuff helps us with the old algorithms to keep getting amazing guests like this.
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Speaker 3: Well, that's talent. An opera singer who tap dances and sings cowboy songs. I wonder if there's anything she isn't good at. Yes. Choosing what shoe to be on.
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