The Time-Crunched Cyclist Podcast by CTS
Coach Adam Pulford delivers actionable training advice and answers your questions in short weekly episodes for time-crunched cyclists looking to improve their cycling performance. The Time-Crunched Cyclist Podcast (formerly The TrainRight Podcast) is brought to you by the team at CTS - the leading endurance coaching company since 2000. Coach Adam pulls from over a decade of coaching experience and the collective knowledge of over 50+ CTS Coaches to help you cut throught the noise of training information and implement proven training strategies that’ll take your performance to the next level.
The Time-Crunched Cyclist Podcast by CTS
Drinking to Thirst vs. Following a Hydration Plan, with Dr. Alan McCubbin
Join Coach Adam Pulford and Dr. Alan McCubbin, a sports dietitian from Monash University, to unpack the complexities of hydration, particularly for those balancing tight schedules. We discuss the essential strategies for pre-exercise hydration, managing fluid loss during workouts, and effective rehydration post-exercise. We also tackle the debate on whether to drink based on thirst or follow a pre-set plan and learn how to create a comprehensive sweat rate profile for varying conditions.
IN THIS EPISODE
- Hydration needs for time-crunched vs. time-rich athletes
- What does 'optimal hydration' even mean?
- The problem with 'overdrinking'
- Practical methods of hydration assessment
- Drink to thirst or follow a hydration plan?
- Putting sweat rate testing data into practice
- The truth about "losing 2% of bodyweight due to dehydration"
- How much fluid should you replace during exercise?
LINKS
-Podcast: Fueling Endurance: https://podcasts.apple.com/us/podcast/fueling-endurance-nutrition-for-runners-cyclists-triathletes/id1542030768
Twitter: https://twitter.com/nxtlvlnut
Instagram: https://www.instagram.com/fuelingendurance/
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HOST
Adam Pulford has been a CTS Coach for nearly two decades and holds a B.S. in Exercise Physiology. He's participated in and coached hundreds of athletes for endurance events all around the world.
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From the team at CTS. This is the Time Crunch Cyclist podcast, our show dedicated to answering your training questions and providing actionable advice to help you improve your performance even if you're strapped for time. I'm your host, coach Adam Pulford, and I'm one of the over 50 professional coaches who make up the team at CTS. In each episode, I draw on our team's collective knowledge, other coaches and experts in the field to provide you with the practical ways to get the most out of your training and ultimately become the best cyclist that you can be. Now on to our show. Now onto our show. Welcome back, or welcome to the Time Crunch Cyclist. I'm your host, coach Adam Pulford.
Speaker 1:We all know hydration is vital for performance in endurance sports, especially the longer we go or the more extreme the environment is. But what does optimal hydration look like for an endurance athlete? Should we be slamming handfuls of salt tablets? Should we be drinking to thirst or should we drink to our plan? Should we try to guzzle as much fluid as possible at any moment, or is there a better approach? Here to discuss all of those questions is our very distinguished guest, dr Alan McCubbin. Alan, welcome to the show.
Speaker 1:Pleasure to be here. Yeah, so for our audience, who may not read a ton of research or have heard of you all the way across the world, could you tell us a little bit more about yourself?
Speaker 2:Yeah, sure, so I'm based in Melbourne in Australia, so it's evening here as it's morning for you and obviously winter for me as it's summer for you. But I work in multiple sort of different areas. So I'm a sports dietitian by trade. I've been doing that for about 20 years now and I sort of do a combination of things. So I work in sort of the research and academic space at Monash University here in Melbourne and sort of do a combination of things.
Speaker 2:So I work in sort of the research and academic space at Monash University here in Melbourne and sort of do my research there, primarily around hydration and electrolytes. But I also work as a practitioner. So I work with a bunch of athletes, a lot, historically speaking, throughout my career in cycling, with triathlon as well. So I did some work with what's nowz triathlon with their high performance program in the lead up to the tokyo olympics and paralympics, and working with a few of those guys and girls still in the lead up to paris. Um, and then, yeah, a whole bunch of different consulting and media bits and pieces, uh, all around a bit of writing for escape collective and then have my own podcast fueling endurance as well. So keeps me busy.
Speaker 1:Lots of different things, but it keeps it interesting as well yeah, no, that's it, and I think, too, like having that the blend of like research and um and practitioner is a really cool way to keep learning and keep evolving with it too, and that's that's what I see out of your work, which is no, I totally agree.
Speaker 2:Yeah.
Speaker 1:Yeah Well, so for our audience, you can tell that we're we're in for a good conversation today. Uh, this is actually going to be a two part um podcast, so be sure to tune in um next week for the part two. Um, but let's just get right into it. What do you say, dr McCubbin? Yeah, sounds good, let's do it All right. So, since a lot of our audience are crunched on time, which could be training time, recovery time or just like I need more than 24 hours in a day, first question to you is are there different needs for time crunched athletes versus the time rich athletes when it comes to optimal hydration?
Speaker 2:Yeah, well, there's probably a couple of different paths to that answer, which is not very time-crunched in itself, but I'll try and explain. So, when we think about hydration, I guess there's a couple of aspects to this. There's being quote-unquote optimally hydrated, and I'm sure we'll get to that shortly in terms of what that looks like just day-to-day and prior to exercise specifically. So that's kind of the pre-exercise side of things. Then there's the you know what is the fluid loss during exercise and how much of that do we need to replace. And then there's the post-exercise side of things. So looking at rehydration after exercise, assuming we've gone into some sort of deficit.
Speaker 2:So, for the time crunch cyclist, that optimal hydration of you know, starting a session well hydrated that's going to be the same. It's pretty well universal. And, yeah, we'll talk about some of the controversial areas around hydration recommendations and research over the years. But one thing that that all of those different camps agree on is what sort of optimal pre-exercise hydration looks like and that you should be trying to achieve that.
Speaker 2:The during and after stuff is a little bit different. Obviously, if you're doing really long training sessions, then there's a chance that you go into a bigger fluid deficit, depending on how much you replace and then post-exercise. It may also depend on how long you've got to replace that fluid before you have to go again for the next session. So again for the time crunch cyclist, if it's maybe two sessions in a day possibly not, but if it is the case, or maybe the triathletes listening then you've got a shorter window of opportunity to actually rehydrate post-exercise as well. So they're probably the key differences, I think, but the overall. I guess what is optimally hydrated is kind of universal.
Speaker 1:Yeah, well, let's speak to all of those, because I do think, in the unique nature of being a time crunched athlete, is sometimes you just a ride and a run, or a ride and a strength? Yeah, I think a lot of our athletes are doing double days that are just a little bit shorter, so we can speak to the hydration um in between as well. Yeah, so, yeah. So we were talking about optimal hydration. I would say, let's, let's pick the doctor's brain. And what is Alan McCubbin's definition of optimal hydration?
Speaker 2:Yeah, it's a really tricky one, to be honest. There was a really famous paper published it was a while ago now, about 15 years ago but it was sort of said measuring hydration, the elusive gold standard, and what they meant by that is there's lots of different ways that you can measure different aspects of hydration, but it's very difficult to define what optimally hydrated actually is or what it looks like. So I guess, at its at its most basic, hydration is the water in our body, and we can describe that in lots of different ways. We can think about the total body water, which is literally called total body water from a scientific perspective, and then we can break that down. Where is that water in the body? Is it inside our cells or outside our cells? We call that intra and extracellular fluid and then the blood volume. So they will all have different volumes, those compartments, but they'll be different for different people. Obviously, if you've got someone who's 6'6 and 180, 190 pounds or something like that, they're going to have a lot more body to fit that water into, and so they're going to have a lot more litres of total body water in each of those individual compartments compared to someone who's maybe, you know, 90 or 100 pounds, something like that.
Speaker 2:So I guess that's the first thing which makes it harder to find. You can't put a litre number on it because it's going to be different depending on the size of the person. So then you think well, do you put a percentage on that? What percentage of your total body weight is water? Generally speaking, for females this will sit around sort of the mid-50s, for males maybe the 60s. For super lean people maybe up towards 70 as well. And so again, even body composition, how much body fat you have, changes what that number looks like. So you can't just pluck a number out of the air and say everyone, all males should be 60% or 62%, because depending on body fat, that may not be the case necessarily. So that becomes a challenge as well.
Speaker 2:So then we start to look at okay, well, can we look at some other aspect of this? Can we look at what's going on in the blood? So not just the volume of the blood, but how concentrated or diluted all the other things are in the blood, and we call that plasma osmolality, all the dissolvable particles in our blood. How much of that is there relative to water? And we can measure that. But it's not a perfect reflection of hydration either, because you can have the same osmolality in different volumes or different volumes and the same osmolality, so that's not perfect.
Speaker 2:And then at the end of that, a lot of people would be probably familiar with using urine either urine color or something like urine specific gravity, if you want to quantify that scientifically. But that's not really measuring how much water is in the body or the concentration of all the fluids versus the solutes in the body. It's actually measuring the kidney's responses to that in terms of what it's doing by either concentrating your urine or making it more dilute to try and bring everything back into balance. And in some ways maybe that is a reasonable reflection. But what's been proposed over recent years has been this model which combines some of these different methods to get a bit of an overall picture of what's going on.
Speaker 2:And the most practical one is what's called the WUT or the WUT method, which combines your daily body weight and urine color and sensation of thirst, because obviously that's our feedback mechanism to try and get more water into the body.
Speaker 2:And so the idea behind this is, if your weight has dropped more than about 1% from its typical sort of daily baseline in the morning and your urine is sort of a darker yellow color and you have a sensation of thirst, then probably you're not optimally hydrated. But if your urine is a relatively clear colour, your weight's kind of what it normally is each morning, and you're not thirsty, then you're probably doing pretty well. Now that doesn't seem all that scientific necessarily, but it does seem to be a cheap, practical method that tends to work pretty well in most circumstances, particularly first thing in the morning. You know we'll get into it, but after exercise there's shifts, rapid shifts when we drink things and when we exercise and sweat. That throw that out of balance. But first thing in the morning when you get up and you want to know, am I well hydrated, that's a pretty good method.
Speaker 1:Yeah, so I mean we're trying optimal hydration, is trying to achieve the optimal, what that's?
Speaker 2:right In the sense of what you're saying.
Speaker 1:Yeah, Exactly, yeah, okay. Well, I would say as the practitioner, without doing a bunch of research, my observation is we know a few things, and that is in life and in training. Drinking nothing is bad. Drinking a lot typically good, but over drinking is also bad. Would you agree with that genre of things? Yeah, absolutely, good summary. Okay, so if? If that is the case, maybe let's go with like almost over drinking first, because a lot of our athletes, a lot of athletes I work with, they're type a individuals and so if coach says good and bad to something, they're going to go with the good and just overdo it. So what is over drinking and what is the problem with over drinking?
Speaker 2:so, yeah, day to day, outside of exercise, if we drink too much, probably not a lot is going to happen. Apart from, we have to pee a lot, we have to go to the bathroom, and it's pretty inconvenient. There are examples, and there have been circumstances where things have gone wrong. There's been a couple of American, I think college American footballers who actually died from water intoxication. Basically, they were given a message that I think they'd been had a history of cramping and someone had told them that they were dehydrated and they need to drink more, and, as you said, they went to the extreme and drank some ridiculous amount of fluid in a very short period of time you know, faster than the kidneys could flush out the excess, and they actually died from, from what's called exercise associated hyponremia, the great irony being that they never got to the exercise part in that particular case, but that is extremely rare, so I won't really spend much time on that.
Speaker 2:What you're referring to, though, is more so what happens during exercise being overhydrated there, and that's going to be when you drink more fluid than what you're actually losing in sweat during exercise. So you would typically see this play out if you were to weigh yourself. You know body weight before and after exercise. If you're gaining weight, that's probably an indication that you're over drinking during exercise. I mean, there's obviously some other ins and outs in terms of weight or weight gains and losses from eating food, opening your bowels, that kind of thing, but they're usually relatively minor. So if you're gaining weight from the start to end of exercise, chances are you're probably over drinking.
Speaker 1:So we're making a nod here to weighing before, weighing after exercise in order to see if we're getting to that optimal hydration or even like over drinking in that way, um, we should probably talk about, uh, like the, the, the fluid loss assessment that you use and fluid loss assessment that really anybody can use in order to distinguish that. So let's talk about that. I mean, what is a good, practical way of a fluid assessment, knowing if I'm drinking too much, if I'm drinking too little, if I'm right in the sweet spot? How would a listener on this podcast do that in their daily training routine?
Speaker 2:Kind of pretty much what we said before. So weighing yourself before exercise, weighing yourself after exercise, the change in weight, if there are no other ins and outs, will be sweat loss. So if you drank nothing during the exercise, you didn't have to pee or open your bowels or anything like that, you would expect you would lose some weight and that will be essentially sweat loss. That relationship is pretty good up to about three or four hours of exercise. Beyond that that relationship between weight change and reflecting fluid change starts to become uncoupled a little bit. But for most people, most of the time when you're going to test sweat rate you're going to be doing sessions of less than probably four hours anyway. So within those scenarios, yeah, that's absolutely fine.
Speaker 2:You can obviously then correct mathematically for you know solid food intake, which is obviously going to be a weight gain. That's not fluid. And depending on what you want to measure you're measuring fluid balance. You know how much have I lost, you know net gain or loss. Then obviously you don't need to correct for the fluid you drank because that's just offsetting what you lost. Or if you want to know the actual sweat rate how much sweat did I lose then obviously you need to account for the fluid intake being a form of weight gain, essentially.
Speaker 2:So, yeah, there's a bunch of calculators online that you can use to calculate this. There's some infographics we were talking about one of them off air just before that you can sort of guide you through and you know, plug this number in here and this number in here and you know the equal sign will come at the end and that'll tell you how much fluid you've lost and what your sweat rate is. So, um, yeah, it's not an easy one to describe in in audio format, so I'd recommend people go look that one up to to figure out the calculation I in the one that we were talking about um, um, off camera, so to speak, is ask your jukin groups, uh, infographic.
Speaker 1:I've cited his research quite a bit. I'll link to that in the show notes. But a couple of questions for you on that. Dr McCubbin is so a time crunched athlete. They dream about a four-hour session. Could they do this in a one-hour session? Could they test their sweat rate in that way?
Speaker 2:Yeah, they definitely could. What I would suggest is probably doing sessions that are at least one hour long, and the reason for that is that when we start exercising obviously our body temperature starts with whatever our resting body temperature is, and obviously we're not sweating at rest, generally speaking, unless you're somewhere really hot and humid. And so you know that first half an hour of exercise, as your body temperature slowly rises to whatever it's going to finally kind of settle at, your sweat rate will ramp up progressively over that period of time, and so if you only capture, say, the first hour of exercise you're probably half of, that is going to be a fair underestimate of what it would have been if it you've extrapolated that out to two or three hours of exercise, something of that nature. So probably I usually suggest to the athletes that I work with a minimum of a one hour session up to maybe a three, maybe four hour session, but kind of one to three is probably the sweet spot.
Speaker 2:I guess the other thing I'd say here is sweat testing is going to vary for a few different factors and I think we'll get into that shortly. But you know really that the pace or power output is going to have a big bearing on sweat rate. So you know, you can do two one-hour sessions and have completely different sweat rates, not just because the weather was different, but because the power, you know, one might have been a zone two ride and another one might have been, you know, just below FTP or something like that, and you're going to have completely different sweat rates coming out of that. So that's important is to understand why you're collecting this sweat rate data and what situation do you want to apply it to, and try and replicate that situation as best you can when you're doing your test.
Speaker 1:And so, just on the very minimum aspect of things, maybe 60 minutes, maybe 90 minutes. In order to get that, I would probably go 90 minutes. Lastly, is there any value in simplifying things, meaning it's 90 minutes, I can get through it. I'm not going to take any fluid in, I'm just going to measure myself afterwards. Is that a simple way of doing it, or would you take fluids in if you're doing this?
Speaker 2:Yeah, look, it depends a little bit on why you want to do the test. If you just want to know the sweat rate, then yes, it does mean less math because you don't have to correct for the fluid intake. So that can simplify things a bit, and I know a lot of athletes or coaches who deliberately go down that path. I tend not to personally. With the athletes I work with, we have like a spreadsheet set up, that sort of does those calculations for them. But what I'm also trying to get a sense of is how much are they drinking compared to their fluid loss? Are they drinking enough to cover the fluid losses or not? And we collect some other data, which we can talk about later on as well, to try and get an indication. Well, if they're not drinking enough during exercise, or maybe they're over drinking during exercise, why, like? What is driving that behavior? And therefore, what do we need to do about it? Because it's going to be different in different scenarios depending on what the issue is.
Speaker 1:Good. So it's almost a behavioral assessment as well as a fluid assessment.
Speaker 2:Yeah, yeah, exactly.
Speaker 1:Gotcha. Okay, well, we'll get into that more of assessment in just a couple seconds here. But what I want to do the question was posed to me from a couple athletes too, and I think it's an evergreen sort of question is all right. We've got this assessment. That's kind of sitting on the table. We have our data from it. Now should I drink to thirst or should I drink to some plan that I deduce from?
Speaker 2:that assessment and that's where having that extra information is so valuable, because you can get a sense of. You know, you can take a measure of thirst. You can obviously measure how much you did drink and that'll give you an idea. You know, you might've gone out with a plan of drinking to thirst and that'll actually say well, where did that actually get me? Did it get me to where I need to be or not?
Speaker 2:I think this kind of program drinking versus drinking to thirst has been kind of built into this false dichotomy over the years, and it's been done so by people who've created it almost to create a controversy for the sake of creating controversy. It's kind of been set up as the David versus Goliath or, you know, the Gatorade versus the anti-corporate kind of argument, which is really unfortunate because it's kind of you know, it's almost like politics, isn't it? It's kind of simplified things into you know us and them, and it doesn't really get to the heart, scientifically, of where we need to go, because you know, drinking to thirst can be part of a plan. You know, then, they're not mutually exclusive. And the thing I always say to people and I experienced this myself in a 100K mountain bike race is. You know you can have a plan. Or you know you can go in saying I'm going to drink to thirst, but if you run out of fluid and you're thirsty, you can't drink to thirst, and then you're in a lot of trouble. And so you know, for me there's two parts to the planning aspect of it. One is the how much am I going to drink, which often thirst is a pretty good guide for that in most cases. But the other part of that is how much fluid do I need available in case my thirst tells me to drink it? And so, if you have no idea about that and that's where you know, going to that real dichotomy or that extreme of it is just saying, oh, sweat rate testing is a waste of time.
Speaker 2:Programmed drinking is a conspiracy, like just drink to thirst. Well, that's fine. But how much fluid do I need to take? Unless you're doing some testing, you're not going to know. Now, obviously, if you're jumping on the trainer at home for an hour, one bottle will probably cover you. You probably don't need to sweat rate test to tell you that. But once you start going longer, or maybe doing a Gran Fondo or some sort of event in hot conditions and you're not sure what that fluid loss and replacement requirement might look like, then you need to figure that out for yourself and you need to figure out well, how much fluid do I need? How am I going to get access to that fluid? And obviously that's different in different types of events, but certainly the planning for me is around the availability as much as it is around how much of that available fluid am I drinking.
Speaker 1:So, essentially, those who fail to plan plan to fail. Yeah, exactly, all right. Well, let's talk about how to get a good plan together, and it's going to swing back to the fluid assessment or the fluid testing. So when we're measuring the sweat rates during exercise, what does that tell us? Say, we did our test XYZ, we did the math, and then we come up with the sweat rate. What does that tell us and how do you put that into practice?
Speaker 2:Yeah, so the number that you're going to get is usually, well, in metric units would be mils per hour of fluid loss, typically, or sometimes liters per hour. Obviously, you could convert that into fluid ounces if you wanted to as well, but that's going to be kind of the number that you're going to get out of that kind of an assessment. Now, obviously, that's the you know over the whatever you know session you've done. That's the average sweat rate over that whole session. So if it was at one pace or power output over the session, that might be pretty good. Obviously, if you've been doing intervals or something, you know, there'll be higher parts, lower parts, but it's sort of giving the average over that whole session.
Speaker 2:The question is then, obviously, what are you going to apply that back to? As we said before, so if you've got a sweat rate test that was done, you know, on the trainer, indoors, for example, that's completely different to outdoors where you've got airflow or it's, you know, a Zone 2 ride, Well, that's completely different to a criterium that you might be racing. Or if it's in, you know, 80 degrees versus an event that's in 60 degrees or vice versa, Again, that's not going to be that helpful to you that's in 60 degrees or vice versa. Again, that's not going to be that helpful to you, but essentially it's going to tell you what the sweat rate was on that day in those conditions at that intensity. And when I say intensity I mean absolute intensity, so actually watts or power output as opposed to percentage of VO2, max heart rate, max FTP, whatever. It's the absolute intensity that's important here, not the relative intensity.
Speaker 1:So do you control for intensity when you're doing the test? Is there, say, for our audience listening, is there um kind of a gold standard or a sweet spot sort of intensity that they should be testing themselves on? Or is it multiple? Is it two or three sort of tests with various intensities? What do you, what do you recommend?
Speaker 2:yeah. So again, it depends, guess, on what scenario you want to apply those results to. So a lot of the testing I might be doing might be with, say, like a long-course triathlete, so I might know well, what's your expected power output on the bike in your Ironman or your 70.3 or whatever it is. So go out and test at that intensity and so we can say, well, this is roughly, at least in those conditions, the sweat rate we would expect at that pace, obviously for really long events.
Speaker 2:The other thing that comes into this is that the weather's not a fixed variable. It changes throughout the day. So, particularly something like an Ironman or a Gran Fondo, that could be quite long you might be out there. It starts really cold in the morning and then gets really hot in the middle of the day. So again, the sweat rate's not going to be a static number. So I think one of the key things with sweat rate testing is it's not like you do one test and you go that's my number, or that's my number at this power, even because that's my number at this power, under these weather conditions, at that speed, with that amount of airflow. It is quite specific.
Speaker 2:So I always say to people. You're not finding a number. You're building a profile, you're trying to get a sense of what's the lowest kind of sweat rate I might expect in my particular event, that I want to apply it to what's the highest sweat rate I might expect in that particular event, and so I'm going to have a range now to work within and that will start to help me planning my fluid. It might be different at different times of the race in terms of you know how much mils per hour I want to replace, and we'll get into that, I'm sure. But it also has implications for things like my carbohydrate intake, because you know some of that's going to come potentially from fluids, some from solids. How much can I get from fluids?
Speaker 1:Well, that depends on how much fluids I can afford to drink, and that might change over the day as well. Building the profile that's the best way to put it and that's, I would say, my observation of my coaching practice has been from here are the ranges to stick to for this event to okay? Here's what could happen in the event. Here's what we know about you historically. You need to be able to change according to the profile when stuff changes and if there's no other message that people listening get from this podcast other than that that's a good one. And so we talked about intensity, we talked about like an environmental, and I would say the third thing that probably plays a role here is clothing. Is there anything that you control for or would advise on what to wear, what not to wear during something like this? There's clothing. It's like whatever you're kind of wearing the same thing all the time. What would you recommend on clothing, as in when you're doing the testing, when you're doing the testing, when you're?
Speaker 2:doing the testing. Yeah, yeah, yeah again, as much as you can try and sort of replicate the same kind of clothing, um, probably that the place or the scenarios where it might vary a lot might be, say, colder weather, where you might be arm warmers, leg warmers, gloves, all that kind of thing that might come off in a race scenario, where they may not come off in the sweat test. So that's probably where there might be some variation there. And I'm sure everyone's been in that situation where you've gone out on a cold day with all of that gear on, you, warm up, and then you get too hot, you haven't got a chance to take it off for whatever reason, and then you're just sweating profusely underneath.
Speaker 1:So again, that's going to be completely irrelevant as a test if that's not how you're going to strip off all that gear in the race or whatever scenario you want to apply it to. That's the exact example I was thinking about. I've done camps and and fondos and stuff like that, where you know it starts cold. You hit the hill, climb the sun pops out and you're not comfortable taking a jacket off and either start start hitting the water a little bit more or pull off to the side, take jacket off and away you go, because that that changes the the game quite a bit. So in this test um for the fluid balance assessment, what are, what are some of like the key principles to take away from that? Is it just the, just the total fluid um that you're looking at, or there are some other things in the body that we're going to train for optimize in order to build the best drinking plan possible?
Speaker 2:yeah. So this is where I think the more information you can capture in that testing, the better. Um, you know, traditionally the test has been. You know, as we said before, go out, weigh yourself before, weigh yourself after, maybe capture the amount of fluid that you drank, maybe capture the amount of solid food you ate, just to correct for the weight gain from that food, and that's been about it. And at the end of that you get a number in terms of this is how much I sweated, total and per hour. This is how much I drank. Um, this was my total deficit. Was it a lot? Was it too much? Not enough? You know, whatever, what I've started doing a lot with with athletes, and this comes from the work I do at the university and and actually not my, not my research, but the other guys at the uni their main area of research is around gut issues, mostly in runners, but obviously it applies to to any endurance athlete and, and so I see a lot of the work that they do in their research around measuring, you know, gut tolerance and things like that, both to food and fluids during exercise and that kind of thing, and so, you know, over time I started to introduce that into the sweat testing process.
Speaker 2:Because, as we said before, you know, looking at those behavioral side of things is to say, okay, if you're not drinking enough fluid during exercise, why are you not drinking enough fluid during exercise? And so the first thing I would always add now to those is a rating of thirst at the end of the session. So you know rate, that you know from zero to 10. So zero, absolutely not thirsty at all. You know 10, you found me wandering the desert after a week, kind of thing, and you're going to be somewhere on that spectrum in between. And then a rating of gut tolerance as well. Again, you know zero, absolutely no gut issues at all. 10, you know, it'll be obvious, it's 10. It's, you know, severe projectile vomiting or diarrhea or something really, really bad has happened, kind of thing.
Speaker 2:And so I guess the point behind all of that is to say, well, if I'm not drinking enough fluid, well, I know how much fluid I took with me, because I measured that. I know how much I drank. I know my thirst rating at the end of the session. I know my gut tolerance to fluid at the end of the session. So from all of those things I can start to build a bit of a picture of what's going on. So if I'm not drinking enough, then I can look at the thirst.
Speaker 2:Okay well, my thirst rating was eight out of 10. So I was thirsty but I didn't drink enough. Okay well, why didn't I drink enough? And then you go hmm, okay well, I ran out of fluid, I didn't take enough. So this was a planning issue, an organizational issue, so I need to carry more fluid with me next time. So that could be one reason.
Speaker 2:But that thirst rating might come back as a two or a three out of 10. And so you're going well, I just didn't drink because I didn't feel thirsty, and so now it's, maybe it's a. Hmm, how do I interpret my sense of thirst? Maybe I need to be someone who tends to kind of push that boundary a bit and drink a little bit earlier in response to thirst compared to, maybe, other people, because there are examples of people that have sort of either become significantly over or under hydrated, despite thirst not really telling them that they were heading in that direction. So it does happen. It's not common but it can happen.
Speaker 2:And then the other thing is the gut tolerance. So you might have the person who's not drinking enough during exercise and their thirst rating is a nine out of 10. You know they're really thirsty, the fluid's available, but they didn't drink it. Well, why didn't they drink it? Because I had gut issues and I couldn't stomach the fluid. So now that's a completely separate issue. You've got to go away and do some gut training to get used to that volume of fluid going in during exercise. Going in during exercise, um, so that. So I guess you know the initial diagnosis I sweated this much and I didn't drink enough to replace it is the same. But now we've got an idea of why didn't I drink enough and, crucially, what do I need to do about it.
Speaker 1:In response, education is awareness and awareness is education, and I play this game with, uh, just intensity rate of perceived effort with my athletes, as well as any fueling sort of game plan too, because I think the awareness, like you said, like, um, I wasn't that thirsty, and it's like, well, you lost three liters. What's wrong? Um, so I do think that this um, this assessment, is very helpful, even if it gives you the same number that you've been putting into practice during your training session. All of a sudden, you become more aware of stuff so that when it changes, you know how to change with it, and that's probably the most valuable thing to pull away from this. So one thing that you said in there was you do the assessment. You assess that I didn't drink enough. What is an indicator that you didn't drink enough?
Speaker 2:So that would be probably based on the amount of fluid or the fluid deficit at the end of the session. So there are different ways you can kind of quantify that, but probably the standard way that we think about both in research and practice, is the percentage of body weight loss due to fluid losses. So we start with whatever your body weight was at the start of exercise. You know we do all the ins and outs of fluid, food and so on and at the end of all of that we have the fluid deficit and you know at the end of that, if that fluid deficit is, you know, a certain percentage of what that initial body weight was. That's kind of the number that we're looking at and it's been controversial over the years of what that initial body weight was. That's kind of the number that we're looking at and it's been controversial over the years of what that number should be and I still don't think we have a clear cut answer. You know, for decades it was 2%. That was kind of the number that had been thrown around.
Speaker 2:What we do know is that most of that research that came to that figure of a 2%. Two issues with that research. Number one is that generally they bring people in the participants in the studies and they would do two trials, and in one trial they would not allow them to drink anything, and in the other trial they would try and replace literally every drop of sweat they lost and then they would look at the difference in those. So of course the group that weren't allowed any fluid did much worse from a performance point of view, so that's not good. Then they would look how much fluid did they lose in comparison to the other group who replaced everything? Well, it was about two percent or more. So that's where that kind of two percent number came from. So firstly, it's setting up again sort of a false dichotomy like you're not allowed to drink at all. Well, if I knew I wasn't allowed to drink, I'd probably perform worse too, regardless of what the fluid deficit actually was.
Speaker 1:just the psychological fact that I'm not allowed to drink.
Speaker 2:So that's an issue in itself. The other issue with those studies is there's no blinding, there's no placebo in here. You know I'm replacing every drop of fluid, or you know I'm not allowed to drink any fluid. Now, if we think about that in any other area of research, like if I was doing a caffeine study and I said you're getting caffeine and we're not giving you anything, I would get laughed out of the room. If I tried to publish that paper, they would say there's no control here, like you're kidding yourself.
Speaker 2:But yet in fluid, that's what it's been for decades, because how do you blind someone to the amount of fluid that they've actually drank? And so in recent times there's been some work to actually blind that properly. And so now we've got three or four studies now where they've actually used nasogastric feeding tubes you know, the same tubes that unconscious patients use in an intensive care unit in a hospital. So it goes into the nose, down to the stomach, and then they put that into the cyclist and then they can, you know, run the fluid into the tube from behind their back so they can't see what's actually going into it, and so they can use that to vary the amount of fluid that's actually going into the stomach, bypass the mouth and the sensation of how much I'm drinking. And so now we're starting to get that picture of what that looks like At this stage.
Speaker 2:We know that probably definitely 3% body mass loss is going to be detrimental from a performance point of view. We know that at about 1.5% the perception of am I drinking or not. So they've now done studies where they've either deliberately blinded them or deliberately not blinded them and compared them or even told them, given them the same amount of fluid, and said we're not giving you fluid or we are giving you fluid to see whether just the knowledge of that influences performance. And at about 1.5% body mass loss it does. So I think what we can conclude from this is that when we blind the studies properly, we can see that it doesn't matter whether it's blinded or not. Once you lose sort of two and a half 3% body mass loss, your performance is going to decline. But at those smaller numbers around that one and a half percent there's probably a placebo effect and so we can't be a hundred percent sure around those sort of numbers at this stage, but it's probably going to be somewhere in the realm of two to 3%.
Speaker 2:The final thing I'd say on all of this and this is another big unanswered question in this research is that most of those studies, yes, they might exercise people for two or three hours at just a constant pace and then do the performance trial at the end, but the performance trial itself is usually at a much higher intensity because they're designed to last maybe 15, 20 minutes or something like that.
Speaker 2:So that's relevant, particularly in road cycling, to certain types of stages where you go along at a kind of steady pace in a peloton and then there's a hill climb at the end or leading to a sprint finish. It probably is representative of that, but it's certainly not representative of something like an Ironman or a 70.3, where it's just a steady state effort the entire time or, you know, a relatively consistent effort the whole time at a lower relative intensity. And so for those lower relative intensities, can we get away with a slightly bigger fluid deficit? We don't know. So there's a lot more research, a lot more water, I think, to go under the bridge in this space, beyond just the age old, 2% under the bridge in this space beyond just the age-old 2% For those listening.
Speaker 1:if they do their own fluid assessment and it's 3% or more, that's bad Work to increase it. If it is, you gained 1%, that's a bad thing. And somewhere between zero down to maybe 2%, that would be somewhere like if you did an assessment to me and I was zero to 2%, don't change anything. Is that the?
Speaker 2:yeah, I think the closer, yeah, the closer you get to zero percent, though, probably the more likely you are to start having to pee during exercise, and that's obviously going to be an inconvenience, um, and so there's. There's probably a little bit of a trade-off there between the inconvenience of that, potentially, versus a little bit more dehydration. Is it actually impairing performance? That's probably the stuff that we still need to tease out, and I've certainly seen data from professional cycling teams where either they've overdrank or they've only lost about half a percent of body mass, and the amount of times they've had to stop and pee has been pretty dramatic. So, um, that that's not performance conducive either.
Speaker 1:So we call that functional dehydration. Yeah, basically, which is a thing? So I mean I guess the the biggest thing is like, yeah, don't think that you need to be, you know, equal, equal loss to intake, right. But then there's the extreme, yeah, and then there's the extreme to stay away from in that somewhere in between, of dialing it in for you in the particular environment. That's really what we're talking about.
Speaker 1:So in in this plan we've only even talked about fluid, and you know we're kind of coming to the even talked about fluid and you know we're kind of coming to the the end of the part one here. But I would say for our audience, like we've only talked about fluid, we haven't talked about electrolytes, we haven't talked about carbohydrates and we I mean we kind of talked about food a little bit in the assessment, but I want to save the electrolytes for part two. But I do want to make a nod to the carbohydrate intake because it means it's a hot topic right now and I think the way that you organize your plan in the way of carbohydrate fluids and non-carbohydrate fluids is is a really good way to think about your fueling plan. So can you talk about how you organize those two things for a plan for an athlete that you're working with.
Speaker 2:So we talked before about, you know, sweat rate testing is sort of building a profile of sweat rates. It's not a fixed number and that's important because on any given day the weather could be a bit warmer or a bit cooler, humidity could vary either through the course of the event or just not what you expected it to be. You know the forecast was wrong and so you know you're never going to get that perfect on any given day. And so the way I kind of set up the, the fluid, as you said, with the carbohydrate, is to say, okay, well, I know I need to get a certain amount of carbohydrate in, and you know that's a whole other topic we won't get into. You know, grams per, but I've got a number that I'm aiming for. Whatever that number is or whatever it looks like, and that's going to be relatively fixed number in that you know, if it gets a bit warmer it gets a bit cooler. I'm probably not going to change that number. I want that to stay constant. But the amount of fluid that I'm drinking may not stay constant. I might get thirstier, I might get less thirsty, it might, as you said, the sun comes out. I start going uphill where I've got less airflow, my sweat rate goes up, all that kind of thing. So the amount I'm drinking probably needs to be dynamic and change, but the amount of carbohydrate I'm trying to get in needs to be fixed, because you don't want to be in the situation where all your fluids contain carbs and then I get thirsty or I drink more. All of a sudden I'm overdoing the carbohydrate and I'm going to run into gut issues and things like that. Or it suddenly gets a lot colder, it starts raining, maybe I don't feel thirsty, I don't drink, and all of a sudden I'm underfueling because I'm not getting in the carbs that I'd originally planned to get, based on my fluid intake.
Speaker 2:So the way I like to think about this is thinking about that sweat rate profile is what is the minimum amount of fluid I'm expecting to need at any given time, no matter what the weather's going to do? So worst case scenario, at the bottom end from a fluid perspective, and so I sort of see that as kind of the cap on the amount of fluid I can dedicate to carbohydrate. So obviously, if it's a hot day, that might be still a fairly high number. I can still get the majority of my carbs from fluids. But if it's a very cold day or some of the ultra-distant stuff where you're going overnight potentially as well, and it gets cold overnight, then that number might be really low.
Speaker 2:It might be only one or 200 mils an hour in some cases, and so in that scenario then you're like well, I can only afford to use 100 or 200 mils an hour of fluid for carbohydrate, so I'm going to have to be much more reliant on solid foods. You know gels, bars, you know real foods and things like that. So yeah, I always plan that. You know that minimum expected fluid intake will be the bit that I can afford to dedicate to carbohydrate, and then the additional fluid will be carb-free fluid, so plain water. It might have electrolytes in it, but it's not going to have carbs in it, and that amount can vary up and down. That's the dynamic part, and thirst will help me decide what that needs to be at any given point in time.
Speaker 1:In my opinion, that's a really good way of organizing your tools out there on the road.
Speaker 1:And I would say, to add to that even more like in road racing, road events, we've got our aid stations too, and this is kind of the fun part is, if you can get the bottle, the availability of fluid could be almost infinity, to the point where, if it does get really hot, we can use some of that fluid to, um, douse ourselves, cool ourselves over the back, and I think, when it comes down to what you just said, it's like, yeah, make sure that you've got some bottles that are not carbohydrate, cause you don't want to be pouring super carb all over your back, so it will attract the bees.
Speaker 1:So I guess I want to close it out there for part one, because we, we, we touched on a lot, we, you know that that fluid assessment, um, part of it, that's really the main thing to drive across, and so, for our listeners, if you've never done a fluid assessment, I highly suggest you do, because it's going to create more awareness, it's going to educate you on what your body needs in certain situations and it's going to give you the tools you need to develop a really good plan for optimal hydration. Dr McCubbin, is there anything you want to add to that for part one?
Speaker 2:I think the final thing I'd add here and this is something I think people don't realize is that we can aim for that, say, 2% body mass loss, 2.5%, 1.5%, whatever figure we want to go with and then we work backwards and calculate OK well, my sweat rate is this If I lose this much, I'll end up losing this percentage of body weight. Therefore, I need to drink this much, or roughly this much, during exercise. If we think about that as a proportion of the fluid loss that we have to replace, that changes depending on the duration or the total sweat loss during exercise. And what I mean by that is that if you want to finish like a criterium that only goes for an hour, with maybe a 2% body mass loss or deficit, you know you might not have to drink anything and you'll still come in under 2% because it's just the event's short. But if I then go out and go to a tap and ride, you know, for eight or nine hours or something and stay, you know you want to stay under that 2%. Well, that number is kind of fixed, but the amount of sweat I'm losing is continuously increasing across the nine hours. So actually I probably might need to replace 85% or 90% of my fluid losses, so that the percentage of the loss that you need to replace will increase as the total duration or the total sweat lost increases over time.
Speaker 2:And I think that's a point that people often miss. They kind of think well, you know, 2% means you know 500 mils an hour or whatever it is. It doesn't matter whether it's one hour or six hours of writing, it's still 500 mils an hour. It's like no, well, it might start off at zero and it might progressively increase to 900 mils an hour, but you're still coming in at that 2% deficit. It's just the mathematical relationship there. So it does become a little bit tricky with that, and I guess that's where you know finding an online calculator or getting some professional advice can be helpful in trying to work all of that out.
Speaker 1:It's a vital bit of it and I would say, having that, that consult, having a coach to maybe make a little bit more sense of that assessment is in put it into place, put it into plan. That's going to be super critical Cause, yeah, that's, that's a really good point. Um, dr McCubbin, about, like, sometimes you know if it's, if it's like NASCAR and uh or criteriums as you use, I mean, you just kind of like burn it hot, let let it drain, because there's some functionality to it. But the longer you go and that was my, you know, the first question of the day the longer you go stuff changes and we'll get into. We'll get into that in part two a little bit more in combination with electrolytes, because that's where, um, I think there's some other uh confusion out there in the way of hydration and and um, cramping and and fueling and all those sorts of things. So, dr McCubbin, thank you. Uh, this has been super enlightening even for me and I think our audience will take a lot away from it.
Speaker 1:Yeah no problem. Thanks for joining us on the time crunch cyclist podcast. We hope you enjoyed the show. If you want even more actionable training advice, head over to train rightcom backslash newsletter and subscribe to our free weekly publication. Each week you'll get in-depth training content that goes beyond what we cover here on the podcast. That'll help you take your training to the next level. That's all for now. Until next time, train hard, train smart, train right.
