Sweat Rate: The Key to Optimal Hydration for Athletic Performance Ep 103

Coach Chris discusses sweat rate, and why it matters more than you think for optimal hydration. Sweat is your body’s primary cooling mechanism—and how understanding yours could be the key to unlocking better performance and smarter hydration. In this episode, we dive into what influences your sweat rate, how to test it, and why it’s one of the most overlooked (yet powerful) tools for endurance athletes.

You'll learn:

🔥 What you think is enough hydration might be way off
🌡️ One environmental factor matters more than you realize
⚖️ A small shift in body weight could mean a big drop in performance
💧 There’s a sweet spot for hydration—and yes, you can overdo it
🔬 One part of your sweat profile never changes (and why that matters)
🏃‍♀️ Why two workouts in the same week could require totally different fueling plans
📈 How to uncover trends in your sweat rate (and what to do with the data)
🤯 Real-world examples that may surprise you

Ready to dial in your hydration and fueling plan?
 👉 Get our free sweat rate calculator (only available through the hydration guide (link below) or priority list for the Fueling & Hydration Bootcamp--and IN the bootcamp)
👉 Join the Fueling & Hydration Bootcamp waitlist at theenduranceedge.com/fuelingbootcamp
👉 Explore home or in-office sweat testing options if you’re ready for personalized support

Experience the breakthrough when everything finally clicks! Train with expert coaches, fuel with incredible chef-prepared meals, and connect with athletes who love triathlon as much as you do. Join us April 22–26 at beautiful Lake Jocassee for four unforgettable days of swim, bike, run, learning, and community. Spots are almost full: Reserve yours here.

Transcript

Understanding Your Body's Cooling System

Speaker 1 1:33

Hey y'all, and welcome back to the Find your Edge podcast. So this podcast is something that I talk about literally all the time, and I have to remind myself that just because I tell it to myself doesn't mean you know it or understand it or how to use it. So today we're talking all about sweat rate, what it is, why it matters, and how you can hydrate and fuel properly in order to have the best performance possible. All right, so let's jump right in. So sweat is your primary cooling mechanism. So when you exercise, your muscles generate heat and then your body sweats to release some of that heat to keep your core temperature in a good range. When it's really hot out, like it is here in North Carolina, and the dew point is really high, so there's a lot of moisture in the air, that becomes difficult. Your body cannot cool as efficiently when there's a lot of moisture in the air. Right, because we want that evaporation off of our skin, but when there's a lot of moisture in there, again, that's not going to happen quite as effectively. So what do we do? This is literally. I mean, we're bombarded with people in the summer who are like, oh my gosh, I am dying. And hopefully that's not the case and we have solutions. I also thought about this today because I had a high levellevel tennis player in the metabolic testing facility today doing her sweat testing, with her main complaint being how much her body just suffers in the summer. So if you are experiencing things like wobbly legs, just feeling like you have dead leg feeling, maybe feeling nauseous, maybe even having dry heaves or actually vomiting, getting intense headaches or starting to see stars, maybe even passing out, then your sweat rate might be the culprit. Also, we can get in a little bit into your sweat concentration. So that's your electrolysis. So we have kind of a couple of different things here going on.

Speaker 1 3:40

But I want to make sure that you guys understand this, at least at a high level, so that you can start to understand your body and fuel and hydrate the best that you can for your sport. So let me emphasize the fact that sweat rate is incredibly individualized and incredibly variable. So, first and foremost, the individualized part. I'm sure that you have seen out if you go out with your local run group or you go play tennis with your friends or whatever it is your pickleball, whatever it is that you're doing football, soccer and you may notice that there are some people that are just sweating incredibly heavily and there are some people who are just barely dewy. Right, you can blame that on just you. Congratulations, you are you.

Individualized Factors of Sweat Rate

Speaker 1 4:29

Now there are some factors that go along with that, like your current state of fitness. With that, like your current state of fitness, you generally tend to sweat faster. If you are more fit, because your body is used to that, it's getting prepared, it's like all right, we're going to start to cool down so that we can manage our core temperature while our body is doing all of this work. And then there's acclimatization. So when you are acclimating to a, let's say, to the summer, it's going to take you a little bit. The first couple of days are probably going to feel pretty terrible, and then you will gradually acclimate to the weather pattern. Pro tip on that is don't overdo it. Always dial back your expectations, give yourself some grace and know that, yes, your fitness will not necessarily suffer, but you've got to be trying to avoid putting your body at risk of health issues by being a little gentler on yourself. All right, so there's one.

Speaker 1 5:35

The other big one that I want to emphasize is the environment. So I'm always harping on my folks who are in the fueling and hydration boot camp, as well as anybody who does sweat testing with me and gets an individual consult with me, is dew point, dew point, dew point. Your sweat rate depends on a few different things and the dew point is one of them. Again, the more moisture there is in the air and the combination of temperature and humidity produces something called the dew point. The higher the dew point, the harder it is for your body to cool. So we have a very specific spreadsheet that we have to cool. So we have a very specific spreadsheet that we have. Everybody use their sweat log and then we can actually compare what is the dew point and how much are you sweating. Your sweat rate will vary.

Speaker 1 6:24

I cannot emphasize that enough. This is something that people come to me and they're like I always drink a bottle an hour on the bike. Now, the bike is a can be a little bit different just because you have some level of convection or if you're outside, that is, and depending on what the conditions are, mountain biking you're going to have a little bit less convection, gravel, a little bit more road, probably the most. So you have some of that helping you cool, but when it's really cold versus when it's really high, hot. So, the dew point being low and the dew point being higher, you may need to drink less when it's low and drink more when it's high. So that bottle of fluid an hour is not, or should not be, a hard and fast rule for you, unless you're exercising literally in the same conditions all the time. Okay, so that's a really important one, to know how your sweat rate varies.

Speaker 1 7:24

The other thing that can vary, as I just mentioned on the bike, can be the sport. So your sweat rate loss when you're swimming versus when you're biking, versus when you're running, versus when you're playing tennis, versus when you're playing pickleball versus when you're rowing a boat on the middle of the water, or paddle boarding or whatever, is going to vary based on the sport and what other cooling factors are there or how exposed you are to the sun and those types of things. So, be sure, if you're going to measure and I'll get into that more here in a be sure, if you're going to measure and I'll get into that more here in a moment if you're going to measure your sweat rate, be sure to identify what the sport is. You can even do this inside, like for weightlifting, because you know there are those people who decorate the floor with all of their sweat confetti all day long. So do this as an experiment for yourself, because so many people just don't know this information. And then they come to me wondering why? Why is my performance terrible? Or why do I feel terrible when, basically, at the end of the day, they're not hydrating properly? So brings me to another point.

Performance Impact of Hydration

Speaker 1 8:27

Your sweat loss, which of course is fluid in your body, is means that you will have a performance decline, and what we've seen in the literature is even a 2% body weight loss can reduce your overall performance, and that can be whether you're picking up heavy things, or you're trying to run a 5k, or you're trying to get out there and play tennis or soccer, or whatever the case may be. So that is a that's from the literature. But I've seen people who are such heavy sweaters and they have just gotten so acclimated to losing more than that, and then some people who just don't do well even getting close to that 2%. They need to be a little bit more like 1%. Now, quick note on that the goal of hydration should not be to match your losses exactly. Your body knows what to do when you lose a little bit. So usually I encourage people like can we aim for somewhere between one to 2% body weight losses? Sometimes it's going to be more, sometimes it's going to be less. Oftentimes, especially for short workouts, we'll see people lose 0.5% 0.8% Great Fine. That% 0.8% Great fine, that's awesome.

Speaker 1 9:40

Again, the goal is not to get completely to zero, and the only reason why I say that is because it's too risky to tip that number in the opposite direction, which puts us at risk, which is why guessing can backfire. At risk, which is why guessing can backfire. It puts us at risk of not only performance decline but things like hyponatremia, especially in very long events. Heavy sweaters or some culprits tend to be women who are out there for five plus hours, especially women marathoners and women who are doing 70.3s and whatnot, who are only hydrating with water or they are over drinking because they don't know their sweat rate. I cannot tell you how many times I've seen this in our sweat testing facility is people who get the message, especially women, who get the message that they need that it's hot out and they need that it's hot out and they need to hydrate, but then they're over hydrating and they're actually not getting the amount of electrolytes that they need Again, putting yourself at risk for hyponatremia.

Speaker 1 10:50

That's just one of the potential risks. There are other things that can go along with that, but anyway, that's the big one. And then, of course, there's under hydrating risks certainly performance decline. You might be cramping, you might be getting too hot, you might be having some level of GI distress, whether it be nausea, so more like upper GI distress, or more lower GI distress, sending you to the port-a-john kind of thing, and then headaches is an especially common one as well. Then there's a sign of do you have an electrolyte imbalance? So are the things with, like weight swings, more cramping. Again, some of the symptoms are similar, things like nausea, confusion, high perceived efforts. So something feels really hard, despite it not being something hard that you ordinarily do, despite it not being something hard that you ordinarily do.

Speaker 1 11:38

So, again, knowing that sweat rate is really important to actually test and then retest and retest. Okay, so how do you actually do it? I try to keep this super easy. What you'll see in like textbooks and the way that I actually used to do it in our sweat testing facility is I would have we'd get people to scales in the restroom, make them strip down, pee and then weigh themselves in the nude. You absolutely can do that. The reason why I don't do that anymore and that and that let me clarify that's both pre and post weight test. You can do that. Post-weight test you can do that. The reason why I typically don't do that is because it's going to interfere with their ability to do it multiple times.

Speaker 1 12:25

So I want to see trends. This is just like you going out and comparing your paces or comparing your RPE or comparing how you felt on a certain day. Whether you do repeated runs, repeated bikes, repeated swims, whatever, doing your repeated sweat test, at least per sport and in a range of dew points. So let's call it seasonally, you will find trends about yourself and it is easier for my athletes that I've worked with and for the folks who we've worked with in the sweat testing lab for them to just get on a scale with their clothes on and if they have any sort of issues with seeing numbers on the scale or there's any emotional attachment or that kind of thing, usually I'll give them something to hold. It can be a flower vase, it doesn't really matter. You can pick up something that you don't necessarily know the weight of, and you can weigh yourself with it before and afterwards, and it's just as easy to have your shoes on. The only thing with post weight is, if you are sopping wet, you're going to want to remove whatever it is that you're stopping wet. If you cannot remove something like your head of hair, then that's okay. Just squeeze it out as best as you can, if that is a thing, if that's possible, and get on the scale again.

Speaker 1 13:50

Consistency and trends. Let me repeat that Consistency and trends are the important thing. If you're just going off of one number, you may be overshooting or undershooting. So if you get some consistent numbers also, sometimes you know your scale might be funky or what it might not be on a level surface. So that's why repeat, if you can.

How to Measure Your Sweat Rate

Speaker 1 14:13

So, pre and post weight, do it in clothing, if that's fine for you. If you are one who's like I, just do it first thing in the morning and I, you know, do my indoor bike ride and then I head back to my bathroom and I do it nude again, great, perfect, I'm not even going to say necessarily. Even better, whatever system you will adhere to in order to get your data trends, please do that. Okay, so do that pre-weight, go out, do your workout. Also rewind Before you do your pre-weight.

Speaker 1 14:46

If you could pretty please, for me, go to the restroom and identify your urine color In a perfect world. Again, this is going to go back to adherence. If you can pee in a cup, amen to that, because then we can actually objectively look at the color of your urine. When you're urinating into something like a urinal or a toilet that has water in it, you're not going to get as best of a guess, but it shouldn't necessarily be clear. It should be like a very, very, very light yellow if you're urinating into a toilet. If you can pee into a cup, that's ideal. I'm sure everybody has peed into a cup at some point in their life and put it into the little window at the doctor's office. That's what you're looking for, is the actual urine color.

Speaker 1 15:30

If you want to get super fancy and we've done this before in our office, but again, this is next level you can do your urine specific gravity. That's a whole nother thing. I did that for my thesis. I had to collect my case studies urine and use a little pipette and put it on a hygrometer, which is urine specific gravity. Anyway, that's next level, don't worry about that. Okay, so we've got our go pee. Check your urine color, cause if you have really dark urine or even yellow urine, you need to go rush out and drink water right away. Okay, so that at least knows like. Okay, are you going into the workout dehydrated? So it's your daily hydration up to par. It's not just about what your sweat rate is during exercise. What does your hydration look like during the day in general? Okay, so, making sure that we're well hydrated during the day doing your pre-weight and then going out and doing your workout A couple of things that you need to record.

Speaker 1 16:24

You need to record I like to do time of day, because if it's morning it might get hotter, if it's evening it might get cooler. So time of day, that's really more for your information, but doesn't necessarily go into any calculations. Temperature and humidity is ideal so that the dew point can be calculated. Ps, don't get scared of this or like be scrambling writing notes, because all of this is going to be in an awesome new calculator. So go to the show notes, click on that. We have a phenomenal new calculator that you can literally just do it right on there. Just enter the temperature in Fahrenheit, enter the humidity. It's going to calculate the dew point for you. It's going to calculate your sweat rate, anyway. So these are the things you're getting.

Speaker 1 17:09

You're going to check your urine color. You're going to do your pre-weight. You're going to record the time of day, the temperature, the humidity. Record the time of day, the temperature, the humidity. Then, when you go out to do your workout, you are going to measure the amount of fluid that you've consumed. Get close, guys. So if your bottle, you know, is an eight ounce bottle, or it's a 24 ounce bottle, or it's a 33 ounce, or it's a liter bottle, whatever it is, do your best to estimate how much you have consumed.

Speaker 1 17:43

Next, head back to your scale. If you're super soaking wet, like if your shirt is sopping wet, take that off, dab off a little bit, a little dab, a little dab, dab with your towel if you can dab off or dry off a little bit as best as you can. Again, I'm not trying to make this overly complicated, even though it probably does at this point, but hang with me. So, dry off, get back on the scale and get that post weight. So by doing that, by your pre-weight minus your post weight plus your fluid consumed, minus your urine output. I didn't talk about that. But if you go pee while you're doing your exercise, you're just going to have to guess or just leave it out of the equation. Just depends on how much. Usually that's not an issue for anybody until they're going for multiple hours Over the duration is going to give you your sweat rate Again.

Speaker 1 18:38

Go to our website. It's a super easy calculator. Don't even bother with writing all this down, just go use a calculator. Promise, okay, repeat it for accuracy in the same conditions and different intensities in different conditions. So the more data you can collect about yourself, the better. Once you start to see in similar dew point conditions and at similar intensities, your sweat rate starts to come out at a similar number. Boom, now you've got empowering data so that you can figure out how much you actually need to hydrate when you go and do that same workout in similar conditions.

Utilizing Your Sweat Data

Speaker 1 19:23

So that's why I like for people, especially multi-sport athletes, who are doing like okay, measure yourself during the swim, measure yourself during the run, measure yourself during the bike. If anything is like oh my gosh, I can't weigh myself at the pool, okay, don't, because honestly, that is the one where your sweat rate is the most negligible doesn't mean you shouldn't have a water bottle on the on the deck or some sort of a sports drink or whatever it is that you've got, but I can pretty much guarantee you that your water loss is going to be not nearly as much as compared to bike run, soccer, pickleball, whatever. Okay, so repeat that to get your trends on your sweat rate. And then again, what do we actually do with this data? And then again, what do we actually do with this data? I like to see sweat rate reported as ounces of fluid per hour. Then in our fancy little calculator, then we see how much is lost and then do you need to drink a little more? Do you need to drink a little less? Do you need to drink a little less? So, for your purposes, just to keep it simple, you can head to our website, link us in the show notes and actually put your data into that to see what you lost, and then you can keep going back to it and then just record your stuff on your own If you want to get a little bit more nitpicky or you don't want to keep going back to that calculator we have as part of our fueling and hydration bootcamp, or if you do a home sweat testing kit with us, or if you do sweat testing in our office, everybody gets access to this fueling calculator that we have developed that will literally tell you by your predicted amount of time that you're going to be exercising for that sport at that intensity, how much you need to be fueling and hydrating with it just does it all for you.

Speaker 1 21:13

So here's the kicker is boy. Wouldn't it be nice to know what your sodium is, your sodium losses in particular, just because that electrolyte is the most significant when it comes to exercise performance or muscle muscular performance. Knowing that is something that you can't just randomly know on your own right. So weighing yourself totally easy to do, but knowing your actual electrolyte loss is a different story. Now I have found in the hundreds of tests that we have done. I have found in the hundreds of tests that we have done does not change.

Speaker 1 21:50

Your sodium is like your fingerprint. Your electrolyte losses are like your fingerprint. It does not change year over year or season over season. The challenge is and this is where this why we're talking about sweat rate is that season over season your sweat rate changes, but your sodium losses don't. So if we create a quote unquote solution or a formula for you, that formula doesn't change, no matter what the season is.

Electrolytes: Your Sweat Fingerprint

Speaker 1 22:18

How much of it you drink is the big kicker. Let me repeat this because I have to repeat this all the time for my clients because they're kind of like okay, so if I go out for this ride, then I just take one of these bottles or two of these bottles, or that is completely dependent on your sweat rate. How much fluid and electrolytes should be in that formula is something that we help people do. So let me repeat that again because this is a really important point. Your electrolyte content in your sweat does not change and we've seen this in our testing. I know in the literature it might change a little bit if you have fitness changes or you gain or lose weight or you go into menopause. I have not seen that myself in our testing. When we have people do repeat sweat tests, it comes out exactly the same. So that piece is like your fingerprint. That doesn't change. What does change is your sweat rate. Are you guys getting this? So, again, your sweat rate will change based on the sport that you're doing, based on the intensity that you're doing it at and based on the dew point right? So when people get sweat testing with us or they do our fueling and hydration bootcamp which, by the way, you can get on the wait list for that at the enduranceedgecom forward slash fueling bootcamp camp, we'll be opening up another cohort, so that's getting all into doing sweat testing with us and getting access to all of our different calculators so that you can manage your trends, your sweat rate trends, to be able to best predict what you need on training and race day or game day, whatever sport it is that you're doing.

Speaker 1 24:09

It is nice to start to collect data Once you get the trends. Then you won't have to do it anymore. Then, once the season changes, then that's a good opportunity to start to test again. Again, season changes, you go into the winter, which we all stop thinking about. That that is the time to do it. Then you can see your personal variation in your sweat rate based on the dew point, your intensity and the sport that you do. It is truly fascinating if you guys do this and if you do this consistently, whether you're listening to this in the middle of the winter or the middle of the summer, a year from now or two days from now or whatever. I would love to see some of your data because holy smokes the data differences that we get athlete to athlete.

Speaker 1 24:50

Let me give you an example of our most recent cohort. In our fueling and hydration boot camp, from sodium losses, we had people vary from 20 milligrams per ounce of sweat up to 80 milligrams of sodium per ounce of sweat. And then for sweat rate especially because right now it's hot in North Carolina and most of our athletes are in North Carolina, but we have some all over the country the sweat rate differences were anywhere from, say, 20 ounces per hour well over 80 ounces per hour 80. That's more than two liters of fluid.

Episode Wrap-up and Resources

Speaker 1 25:30

And I've seen some anomalies here and there of people who are unassumingly heavy sweaters. So I've got a lot of really petite women who can just sweat your butt right off. I tell you what gold star for them, something you don't necessarily want to be really good at. But I have seen some women who can sweat so much and some men who don't sweat a lot and some men who do sweat a lot. So it's really nothing that you can adequately predict, but oftentimes you know yourself in that. Are there white sweat rings on your hat when you're done, or are your shoes squishy when you finish and you look at your friends and you're like they're barely even sweating. What the heck? It just makes you special. That's it. That's all right. It's not necessarily anything wrong with you, although we could get into a whole nother discussion about things like pots and other things that may affect your sweat. So hopefully that was the Reader's Digest version of sweat rate why it's important, how to actually test it, how you are super different and unique and why it's important to have all of your trends and then how you can form much better when you get this right and I promise you it's totally possible.

Speaker 1 26:52

So again, head to our website. Click in the show notes below so that you can get access to that sweat rate calculator. Try it out yourself, have some fun with it. Or, if you want to go even deeper, sign up for our wait list for the next fueling and hydration bootcamp when that opens up next. Love to see you there.

Speaker 1 27:07

You can always do a home sweat test kit. Or, if you are local and we have people all over the state who come to work with us, you can do the sweat testing in our office and then you get a one-on-one consult directly with me and I walk you through this whole process, walk you through all different products. We don't have any allegiance to any products, so it's not like oh, we can only recommend Gatorade products, or we can only recommend precision hydration products. Nope, doesn't matter to me. I want to make sure that you are getting exactly what you need for your taste, for your gut and everything that works best for you. Okay, you're awesome. Keep on sweating, keep on doing the thing, and I'll catch you next time. Thanks for listening.