The Time-Crunched Cyclist Podcast by CTS

The Science Behind Sodium and Electrolytes in Exercise Hydration

July 03, 2024 • CTS • Season 4 • Episode 203

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IN THIS EPISODE

  • Role of electrolytes in the body
  • Do we need sodium in sports drinks for performance?
  • Why is sodium in sports drinks?
  • Do we need sodium in sports drinks for 1-3 hour events, or only longer events?
  • The role of electrolytes in cramping
  • Sodium testing
  • Pre-exercise sodium intake
  • Sodium loading for fluid retention before specific events
  • Sodium bicarbonate

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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GUEST
Dr Alan McCubbin works in the Department of Nutrition Dietetics & Food, Faculty of Medicine Nursing and Health Sciences at Monash University as a Senior Teaching Fellow. He is an Accredited Practicing Dietitian and Accredited Sports Dietitian, and in 2021 was awarded Fellowship of Sports Dietitians Australia for his combined research and education contributions to the profession. Alan completed his PhD at Monash, focussing on the dietary sodium intake practices of endurance athletes, and the likely implications for health and performance during exercise.

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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Speaker 1:

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 on to our show.

Speaker 1:

Okay, we are back with Dr Alan McCubbin, and in part one, we talked primarily about fluid assessment and fluid balance when it comes to optimal hydration and fueling for endurance athletes. Today, in part two, we're going to talk about what role electrolytes play in this whole game, and I think that there is some confusion out there in how much salt to take, in how much of these other things like potassium, magnesium and chloride that we actually need. So we brought in the expert and Dr McCubbin to tell us all about it. So, dr McCubbin, that's the question what do electrolytes do for us and what role do they play in optimal hydration?

Speaker 2:

Well, I guess the first question is you know what is an electrolyte? And I guess that the quick and simple answer to that would be different types of minerals that are typically soluble in water and found in different water compartments of the body, generally speaking. And so the ones we tend to think of are going to be sodium, potassium, chloride, calcium, magnesium, that kind of thing. So in terms of what they do in the body, obviously each of those will have slightly different roles. Potassium, for example, is mostly on the inside of our cells in the body and maintains kind of the concentration of water versus dissolvable bits there, whereas sodium and chloride are primarily on the outside of the cells, so in our blood and what we call the interstitial fluid, which is the fluid sort of between the blood and surrounding the outside of all of our cells. And sodium and potassium have this real sort of balancing act where they you know that osmolality how many particles versus water is in the inside of the cells versus the outside actually dictates where water flows, because water will flow to balance those two out. So it'll go from the higher concentration of particles to the sorry, from the lower to the higher, to bring them into equilibrium, and so those electrolytes have an important role, firstly in dictating the movement of water throughout the body, between the inside and the outside of the cells. But sodium has a particular role also in dictating a sense of thirst. So it's the main electrolyte, along with chloride, in our extracellular fluid, the fluid outside our cells, so our blood and our interstitial fluid. And it's our blood that is circulating through our brain and gets detected in terms of that concentration or that osmolality that then signals to our sense of thirst and signals to our kidneys to either produce more urine or produce less urine and conserve water essentially. So sodium has a couple of roles here. It's not just the movement between the inside and the outside of the cells, it's also the regulation of the total water in the body, because it's going to drive that behavior to want to drink more or less, depending on the scenario, and to either conserve fluid by the kidneys or pee out more and go to the toilet a lot and get rid of all of that excess fluid should that be the case.

Speaker 2:

They have other roles in the body as well, of course. You know potassium in terms of the function of our heart muscle. Calcium has a similar role in the blood, obviously, the majority of calcium in the body is actually found in our bones. It's the main mineral in our bone mineral content. But you know there's a very small amount in the blood and that amount is critical to multiple functions in the body. You know heart function being one of them, but conduction of signals between nerves and things like that is also another one.

Speaker 2:

Magnesium has a multitude of roles within the body. Again, not necessarily always in the blood, although there is some in the blood, but there are other roles for that as well. But sodium and chloride are probably the ones that we tend to focus on the most during exercise because they're the ones in the largest concentration in the blood. They're the ones that influence that drinking behavior and what the kidneys are doing from a hydration point of view, and they're also the ones that we not only lose in the largest quantities in our sweat, but they're the only ones of those that are actually regulated in the sweat. So the sweat glands can actually adjust to either get rid of more or conserve it in the body, depending on the situation.

Speaker 1:

So that's a that's a vital component to that and I think it helps in in framing up the conversation that we have, because I mean, I'm going to give it to, in layman's terms, correct if I'm wrong, but our, our body's governance of sodium and chloride is very liberal, whereas magnesium, potassium and calcium is very conservative, meaning there's protections in place to not lose those electrolytes as much as the sodium chloride. Is that right?

Speaker 2:

uh, not quite. I mean, the main reason you're right that we don't lose much potassium, sweat, calcium and magnesium in sweat. You're absolutely right there. The main reason for that is that there's just not many much of them in that extracellular fluid. So most of the potassium, as I said, is on the inside of the cells, not the outside. So it's not in that pool of fluid that the actual sweat glands draw up to produce the sweat in the first place.

Speaker 2:

And the same goes with magnesium and, as I said, calcium. We actually have a very small amount in our blood and the rest of our extracellular fluid, and so it doesn't appear in great quantities in our sweat glands. And it's probably why it's not regulated in our sweat glands either is that there's such a small amount that you don't really need to actively work to either conserve it or get rid of it, you know, depending on the case, whereas sodium and chloride because they're the main ones in much, much larger quantities in that extracellular fluid where the sweat rate's being or the sweat's being produced, we can lose huge amounts during exercise, and so there's going to be some regulation going on there for both sodium and chloride, and they tend to be regulated together.

Speaker 1:

So wherever sodium goes, chloride follows and all vice versa, and so I guess, like where I was going with it is just the supreme kind of like deduction of if I can lose a lot of sodium and chloride throughout the day exercise, non-exercise, whatever but I can't lose magnesium, potassium and calcium. Therefore, I need to consume more sodium chloride than I do these other sort of electrolytes. I don't have to be as concerned about these electrolytes. Is that a very simplistic way of thinking about it?

Speaker 2:

From an exercise point of view, totally agree. Just from a general health point of view, outside of exercise, not necessarily because, um, you know, the the absorption of those nutrients from the gut, from food will will vary, uh, and there'll be some regulation going on there and they go off to other parts of the body as well. So it's not necessarily that we need less, um you know, calcium and things like that. But I guess, particularly in the context of sweat losses and replacement, yeah, absolutely yeah, okay.

Speaker 1:

Yeah, that's kind of like the framing up, basically getting to the point. I don't advise anybody dumping calcium potassium magnesium into their sport drink. I guess that's my. I should have led with that.

Speaker 2:

Yeah.

Speaker 1:

I don't think that there's a need for that. Is that correct?

Speaker 2:

Yeah, well, it's interesting because there are products that do exactly that. There are products that are really high in magnesium to probably less extent potassium and calcium, but particularly magnesium. There's a lot of drinks that are designed for consumption during exercise that have got huge quantities of magnesium in them. We've got one here in Australia that's been around for 25 or 30 years and never ceases to amaze me how much magnesium is in it. But yeah, I don't really see the need to be honest, because the amount that we lose in our sweat is so tiny it's like well, do we even need to replace it?

Speaker 1:

Yeah, I wanted to make a note of that. I did a podcast on, I think, potassium in in sport drink and kind of deduce that and it led to some other questions from audience members. So I wanted to kind of make that as the first note. But as we focus on electrolytes in general sodium and chloride where my brain goes is always kind of like starting with performance and do we need sodium for performance in our sports drink? If we put in sodium chloride, sodium citrate, sodium bicarbonate, that's a tricky one. Is that going to make me go faster? And I'll turn it over to you. You can take it in any direction you want.

Speaker 2:

yep uh well, the sodium bicarbonate. We might park to the side because it's the bicarbonate part there, rather than the sodium that's having an effect, um.

Speaker 2:

But if we think about sodium itself, generally speaking, no um. Actually, as part of my phd I looked into all of that um, the studies around sodium performance. The first thing I'd say is there is very few of them. But the ones that are out there, only one actually shows any benefit. The majority don't show any difference. And also when you go into the lab and do sort of steady state work and you measure things like rating of perceived exertion, how hard you feel you're working, heart rate responses, body temperature responses, all that kind of stuff, you don't see any differences either. The caveat I would say around that is I think sodium may only play a role in performance if it results in a difference in hydration in terms of the amount of fluid you replace. And if that is to the extent where it's beneficial, then there might be a sort of indirect benefit. But there's no direct or independent effect of sodium on performance per se that we can see.

Speaker 1:

No. So if there's an audience member that's like their mind is blown by this right now, it's like why? And their question is why is there so much sodium in my sport drink? Then what's your response?

Speaker 2:

to that. So there's a few different reasons that we might want to replace sodium during exercise and I'll sort of go through them sort of step by step and some of them, uh, I guess, uh, more I guess scientific or things that we might want to quantify with testing and things that we get into, and some of them more sort of behavioral taste perception, that kind of thing. So I guess the first one is, if we think about that classic line from seinfeld, these pretzels are making me thirsty. You know, often sodium will drive greater fluid intake. Now, depending on the situation, that might be beneficial, it may not be beneficial.

Speaker 2:

There's been some suggestions in some research that actually it could go too far the other way and end up in drinking too much during exercise. But I think that the amount of sodium intake would have to be also excessive to result in that from what I've seen. So one of them is around driving drinking behaviour and that may be a little bit different just day to day sitting on the couch at home versus during exercise. But the research is kind of mixed on whether actually adding sodium to your drinks will make you drink more. Um, during exercise if you you're free to drink as much or as little as you want. Uh, we did a study, published it last year. Um, we made some nine poor suckers run on a treadmill for five hours. In uh was it 30 degrees. So what's that? 86, 86.

Speaker 1:

Fahrenheit In freedom units.

Speaker 2:

Yeah, that's right. So five hours and we found basically no effect on the amount that they were free to drink or not drink. Other studies have found an effect, but it varies. It probably also depends on whether you give that sodium, maybe in capsules, versus if it's just in the liquid form where you can actually taste the salt in your mouth. That hasn't really been explored yet whether there's any differences there, but there may well be. So yeah, I guess that's.

Speaker 2:

The first one is driving that drinking behavior, and so sometimes with athletes you may want to drive. We talked about in the last episode the fact that some athletes just don't drink enough and they don't have that kind of sense of thirst that's driving them to drink. So maybe in that case the sodium is going to be beneficial from driving the behaviour that you want. But it's not sort of a universal thing. The other aspects of this will be you're replacing the sodium loss. Obviously, when we sweat, we're losing water and we're losing sodium. Now, generally speaking, we actually lose more water, relatively speaking, than we lose sodium. Our sweat sodium concentration will always be lower than our blood sodium concentration. So if we go out and exercise, don't eat or drink anything, and we just start sweating a lot, our blood sodium concentration actually rises despite the fact that we're losing sodium, because, yes, we're losing sodium but we're losing even more water in our sweat. So blood sodium concentration goes up and that signals to the brain to make us thirsty. It signals to our kidneys to produce less urine and to conserve water. So if we start replacing sodium, that will exacerbate that. So it'll make us thirstier theoretically It'll make us retain more fluid, but also that the more sodium we have in the blood relative to water, again that's going to have that osmotic effect and drive water from the inside of the cells into the blood. Now it turns out when we look at a whole bunch of different research papers, the effect of this movement of water between the inside and the outside of the cells actually makes very little difference to RPE, to core temperature, to heart rate. It seems that the total amount of water in the body, regardless of whether it's on the inside or the outside of the cell, seems to be the most important factor. I don't think we really fully understand why, but that certainly seems to be the case. So that's the other thing is shifting the fluid around. But I don't think that's really a reason to replace sodium.

Speaker 2:

And then the last one is, I guess, around managing that concentration of sodium and therefore the osmolality in the blood. So we'll get into this shortly, I'm sure. But if we drink nothing, as I said, that will rise. But if we drink too much it will fall. But there's going to be a sweet spot in the middle and that's what some of my research recently has been looking at is well, where is that tipping point? Because at some stage it's going to go from blood sodium going up and osmolality rising to the reverse happening and it falling.

Speaker 2:

And again that's been quite kind of dichotomous in the past.

Speaker 2:

It's sort of like drinking too much is bad, so therefore you should just drink to thirst.

Speaker 2:

But there's going to be a bit in the middle there and the crossover point will vary a little bit depending on how salty your sweat is, but it's somewhere between kind of 60 and about 80 percent of of your sweat fluid loss is being replaced. So if you start drinking enough to replace more than about 60 to 80 percent of your sweat losses, then blood sodium will start to fall, even though you're not technically over hydrated and, as we mentioned at the end of the last episode, for really long events you actually then blood sodium will start to fall, even though you're not technically overhydrated and, as we mentioned at the end of the last episode, for really long events you actually need to drink that much to not get into that kind of 3%, 4%, 5% body mass deficit from fluid. And so that's where I think there is a legitimate role for sodium replacement during exercise. It's more the ultra-endurance stuff, it's to balance the fluid replacement, not necessarily as an independent effect, but to balance the large amount of fluid that you have to replace to maintain a reasonable hydration status.

Speaker 1:

Okay, well, that's a lot, so let me see if I can pull on a few threads there. The electrolyte needs aren't. Assuming that we good pre-hydration coming in, we're eating a good kind of um, balanced diet of we have enough energy, we have enough electrolytes and things coming in, our electrolyte needs during exercise likely will not exponentially change or increase until we're probably after that four hour mark we're in some sort of extreme environment. Is that what you're saying?

Speaker 2:

Yeah, it's basically when you get to the stage where you're drinking more than about that kind of 60 to 80% of your sweat losses back again.

Speaker 2:

So if you're sweating at, say, one liter an hour and you're drinking more than about 700 mils an hour, then theoretically your blood sodium will start to fall if you don't intervene and drink something or you're going to force your body to draw on some internal store of sodium which we haven't really studied yet.

Speaker 2:

So we don't know how reliable that is unless we take some sodium during exercise. Now if we think about shorter events, you know we talked in the last episode that if you're doing a one hour criteria you may not have to drink anything to come in below that two percent body mass loss. So if you're replacing a one-hour criteria you may not have to drink anything to come in below that 2% body mass loss. So if you're replacing literally 0% of your fluid losses or only like a few sips 10%, 20% replacement, which is typically what you see in those shorter events anyway then there's theoretically no need for sodium to balance that fluid loss. But once you start to get, as you said, sort of four hours plus and particularly kind of your eight, 10 hours plus, then, theoretically, your need to replace fluid is going to be yes, I need to drink. You know, 80%, 85, 90% of my fluid losses back. So I don't end up, you know, 3%, 4%, 5%, dehydrated.

Speaker 1:

That's when, if you don't take any, sodium, your blood sodium is going to start to fall, and so if, if I have a sports drink with sodium in it and my training sessions and my races are like three hours and less, should I be concerned? Should I? Should I not take all those electrolytes, and is it going to do anything harmful to me?

Speaker 2:

No, it's not going to do anything harmful unless you're taking some ridiculous quantity, and that will usually yeah, it'll usually be like excessive, like capsules or tablets or something like that. Um, you know, double what you're losing, kind of thing. So you know, you, it obviously depends on how much you are losing and that's highly variable. But, yeah, if you're taking, you know you don't need to replace more than 100 in any circumstance. So you know, any time you're taking in more than you're losing, both water and sodium is not going to be helpful and if that happens it'll make your blood sodium go up and up and up and then you can get to the stage where you feel really unwell, kind of nausea, maybe vomiting, something like that. But you'll know, if you ever end up in that scenario, you'll know about it.

Speaker 1:

Yeah, so if we have a listener and they did the fluid assessment test that we talked about, right, and they determined that they have a high sweat rate, they're kind of in that 2% sort of 2% to 2.5% sort of thing. So I need to drink more, but I don't like the taste of water. I like the taste of salty and sweet water, so that would be kind of like a season to taste, so to speak, in order to get me to drink more. That's really a primary role in the, in at least the, the sodium component of what's in a sport drink. Is that what you're?

Speaker 2:

saying yeah, yeah, absolutely. And I guess the key thing there, as you said is, is that season to taste component. Like you're not going, I need specifically this many milligrams per hour of sodium based on my sweat losses. You don't even need a sweat test to do this. You just need to work out what tastes good and what's going to drive the drinking that you want to drive, and that's about what it tastes like. It's got nothing to do with your sweat losses, necessarily. So I think that that's a key message. There is that, for those shorter events, it's not saying don't take sodium.

Speaker 1:

It's just saying that the amount of sodium you take, it doesn't require a sweat sodium test to tell you that exactly, and I think for some people, this is going to be revolutionary because we've been told electrolytes are the god and goddesses of, of performance, endurance and cramping, which we'll talk about here in a second. Um, but it's not. And but you should also still not not take it in. There's value in taking it in, especially when it's driving you to to drink more, whether it is thirst or palatability, um, or or something like that, and I know for me personally, um, it that generally is better, but I think the way to frame it is you're creating a profile of when to take in more versus not.

Speaker 1:

And we're brand neutral on the podcast, but I think this would resonate with a lot of people where, if I'm out doing hard races or training in hot environments, like a scratch super fuel that has about 400 milligrams per serving, that serves me really well in cooler environments. Something like morton, which is also a high carbohydrate drink mix, but it doesn't have a lot of sodium. That sits a little bit better for me. I don't know exactly why, but it tastes better in that way. Therefore, that's kind of how I gravitate or that's sort of my profile. Um, is there anything like in that way? Where would heat be driving a little bit more of that like salty taste, or is it just like that's kind of my preference, would you?

Speaker 2:

say, um, I, I think sometimes it might a little bit in terms of the hot environment, but I think a lot of it is personal preference, and I would certainly say that duration drives that a little bit as well. And so for any of the ultra distancedistance athletes out there will understand this where you get six, seven, eight hours into an event and you just pull a gel out of your pocket and you look at it and you just want to cry because you're just sick of sweet, sticky stuff over and over and over again and you're just begging for a packet of crisps or something really salty just to mix it up from a flavor point of view. And so that's that's probably the other role I didn't mention before around sodium. It can just be around the, the flavor profile and what we call flavor fatigue. That can happen during those sort of ultra distance events as well.

Speaker 2:

So whether it's running, cycling, triathlon, it can happen in all of those, um, probably worse in the heat, but it is very individual as well, and so you know you really have to experiment around yourself to find what that looks like, and often you know you're never going to well, very few people are able to train that duration.

Speaker 2:

They'll only experience it in a race situation, which is hard because then you don't get to experiment around with the real thing, so to speak, and so you kind of have to anticipate that that might happen. Um, because you can't really experience it for yourself until you're in that situation, and then it's too late if you haven't got the options there that that you need in that scenario. So, uh, you know, I've run out of hands and feet to count the, the number of athletes I've worked with, where they're like, oh, oh, I'll be fine, I don't really like sweet stuff and then they come back after the race with their tail between their legs, go, yeah, I should have taken some savory things with me because I, uh, I just got sick of it and I couldn't eat or drink it anymore.

Speaker 1:

A quick story and fun fact I can no like I can no longer have the double espresso goo gel, because there was. I did um i'veRuta several times, but there was one year where that's all I brought with me the for the entire four days, and that's when it was four days. I can't even look at it now without being like, like wanting to, wanting to barf. So, yeah, yes, changed up, uh, the, I call it a, an emotional palette, and that does change in that you should note that as your profile um, where your palate will change and it's telling you to have something different texture, salt, sweet, those sort of things. I made mention of cramping and a lot of people and I was even taught this as a young coach. Quickest way to prevent a cramp is to take a thousand milligrams of sodium, of sodium. I was taught that early on. I know that's not the case anymore, but for those who do think that cramping is all electrolytes, could you please explain the complexity of cramping and maybe we call it something else, such as a syndrome or something.

Speaker 2:

Yeah, absolutely, cramping is an interesting one. It's super hard to study because it's not like you can, it's not consistent, it's not predictable. You can't really bring people into the lab and go okay, well, when I count to 10, you just cramp for me, so I can measure it. It's tricky, um. So over the years they've come up with models, like you know, attaching electrolyte electrodes to people in various places and basically electrically stimulating the muscle into the cramps and then trying to work out, well, how much do I need to zap them? And calling that a cramping threshold frequency and using that to try and differentiate things. But I guess where we've got to over the years now is, as you said, this description of cramping as a complex syndrome, and I liken it to gut issues during exercise, and the official term these days is exercise-induced gastrointestinal syndrome, which reflects the fact that you know gut issues.

Speaker 2:

There's lots of different factors that can contribute. They can be different factors in different people, they can be different factors in the same person on different days and they can add together and we now suspect the same is true with cramping. There's a whole lot of different factors, some of them originating with the muscle itself, some of them originating with the nervous system, which obviously controls the contraction of muscles, and there's a whole bunch of different factors. Some of them have got absolutely nothing to do with nutrition. In fact, most of them have nothing to do with nutrition or hydration or electrolytes nutrition. In fact, most of them have nothing to do with nutrition or hydration or electrolytes. But eventually you know a certain combination or recipe, if you like, of different factors come together and you know when they add up to a certain extent or degree, then you know the cramping starts to happen and most people that are regular crampers will probably relate to this.

Speaker 2:

Like you can kind of feel it, and particularly on the bike, I think like from my own mountain biking experience you can kind of feel when you're starting to go from a cramping perspective, you feel that kind of twinge and you know, if you just back off the power a little bit, you can kind of just sit under that kind of threshold and sit there and be okay. Now, often that threshold is pretty pathetic and you're not very happy with the the power that you're putting out, but you can survive sort of below that threshold and maybe that threshold lowers as time goes on. Um, but it's only when you cross that threshold, for whatever reason, you know, you get to a hill, or on a mountain bike, you get to a rock and you've got to get out of the saddle and push a bit harder to get over the rock or whatever it is that. And then then it goes and you're cramping. Um, and so there's a whole bunch of different factors that have now been implicated, everything from body temperature, both physical and psychological stress.

Speaker 2:

One of the things I think is really interesting with cramping is a lot of people say, no matter what I do, no matter how hard I try, I can never, ever, ever cramp in training. And then every time I get to a race, I cramp. You know, I try to simulate the, the intensity, I try to simulate the duration, the weather conditions, the nutrition and everything, and I still can't replicate the cramping in my training. And so I come to the question of, well, what's fundamentally different about race day compared to training? And and often it's anxiety as much as anything it's's the psychological stress.

Speaker 2:

Yeah, and you know that has a real impact on your nervous system, which, of course, is in control of muscle contraction. So there's a whole range of different factors in here, and one of the things we see. If we go historically back through the electrolyte research was yes. If you go back to when the Hoover Dam was built in the 30s, you know adding salt to things helped people with their cramping. But you look at why it was because they were drinking too much, they were overhydrated, they're actually developing hyponatremia, so low blood sodium concentration from drinking all this water and you know in excess of what they were losing, whereas actually dehydration, as we talked about before, your blood sodium goes up and, if anything, that seems to be protective against cramping, yes.

Speaker 1:

As everyone can listen to that cramping. It's evolving and so if you're one of these listeners, that's like what this changes everything that I knew about cramping, I guess, as like what this changes everything that I knew about cramping, like, I guess, welcome, but don't feel ashamed like we've all been there, um and. But I do think that as we keep on exploring this field and we learn more and at least acknowledge the fact that it's not one thing, it's not two things, it's many things. It's dr mccubbin described, it can help you in creating that profile of when you cramp versus when you don't cramp. I know from like from practice, from my coaching practice. There's also a lot of specificity of training that goes on into it. So if you don't do steep hill climbs in your training, then you go do an event that has a lot of anxiety and effort and you do steep hill climbs and your muscles aren't used to it. That's when a lot of people cramp. So there's the specificity of training and all this kind of stuff.

Speaker 2:

But please don't think that you can just drink some electrolytes and and have your cramping go away, because that's a poor plan when it does happen yeah, absolutely, and I think with cramping there's always been sort of remedies over the years for when you do get to that situation where you're cramping, whether it's's you know salt, you know some people even just like lick a thing of salt, or you know salt tablet on the tongue or something, and some people swear they get relief from it. And maybe they do, I'm not to argue otherwise. But you know, other people have used pickle juice or apple cider vinegar and all those kind

Speaker 2:

of things over the years All sorts of different home remedies, all sorts of different home remedies and, and you know, for every five people that say, oh, it's amazing, it's a miracle cure, there's another five people that say it's absolute rubbish, it didn't work for me.

Speaker 2:

And I think, again, that talks to the complexities of cramping, that you know it might be the same outcome and the same experience, but it's probably different factors that are contributing to it in different people. As you said, the muscle fatigue is a huge part of it as well. Um, so, yeah, it's complex, and because it's complex, yeah, we try and prevent it by throwing everything at it in terms of what do we know are the risk factors and how many of those can we kind of mitigate or control for beforehand. And then you know, when you get in that situation, there might be things that help, there might not, and it might be different in different people. So I think there's a lot more water to go under the bridge. As you said before, we fully understand that Cramping research is not really a sexy area of research. There's very few people worldwide that do it, and so it evolves incredibly slowly, unfortunately.

Speaker 1:

When we talk about sodium, we're talking that for performance. It's not really a huge driver In the way of preventing cramping. It's not doing too much there either in the way of preventing hyponatremia, as you talked about, yes, but it's more like the balance between the water and the salt and and and that kind of susses out over time, so long as you don't restrict one or the other. But even in the kind of this genre of like functional dehydration, there's some prevention that can go on there. If you're, if you're a little bit low on dehydration, that sodium concentration is still okay. So the body is is kind of regulated with that.

Speaker 1:

Um, when it comes down to it, we I mean we mentioned the season to taste and and, and part one of this podcast was all about fluid intake being the most important, as you acknowledge. I mean there are these kind of thresholds or tipping points or durations where sodium is important. So I don't mean to like bash sodium, you definitely need to use it. So let's talk about that sweet spot of where sodium is needed. And then what I want to do is talk about beyond the sweet spot. Let's talk about sodium before exercise and how that can be part of the plan in your profile when you're going especially short intensity but also maybe some long stuff. So maybe let's talk about your research and the sweet spot of where we do need to start taking in more electrolytes, and I think we mentioned kind of beyond four hours or that 60, 80% of your intake for multiple hours. Tell us a little bit more about that.

Speaker 2:

Yeah yeah. So that research sort of started off. I did some mathematical modeling, so certainly not my model, I don't want to take credit for it. It it came from a bunch of nephrologists at ucla, of all places, but they they came up with a model which is based on some earlier sort of physiological work, going all the way back to, I think, the 40s or 50s around, sort of looking at the ins and outs of water and and electrolytes from the body and, um, you know, in in clinical medicine when you're giving intravenous fluids, how much do you need to give to kind of get the balance right. And that was subsequently used in some exercise studies and showed to be pretty accurate in terms of predicting changes in blood sodium depending on water and sodium ins and outs.

Speaker 2:

But it was always used historically in terms of what will my blood sodium end up? You know, is it going to go to go up down? Stay the same, based on the sodium ins and outs, the water ins and outs. But it's an equation, it's algebra, so you can rearrange the equation to change what's on the left of the equal sign. And so that's what I did and I put the sodium intake on the left of the equal sign, in other words, given a blood sodium concentration of this, so you can sort of look at the normal range. You want to end up where it started. You've got a certain sodium loss from sweat. You've got fluid ins and outs. How much sodium do I need to take to achieve that? And basically what that modeling showed was, as you said before, like once you start replacing more than about 60 to 80 percent of your sweat losses in terms of fluid, your blood sodium will start to drop unless you consume sodium as well.

Speaker 2:

Now, the four hours or the five litres of fluid that you mentioned before is Again looking back at. Well, in what situations do you actually need to replace more than sort of 60% to 80% of your fluid losses? And that is sort of where you come to. So more than sort of four hours or more than about five litres in total of fluid loss. Obviously that could be any combination of you know one litre an hour for four hours. It could be half a litre an hour for eight hours, also 10 hours. You know two litres an hour for a much shorter period of time.

Speaker 2:

So it'll vary a little bit there, but it's really when you need to sort of more aggressively replace the fluid. You need to start to balance that out with some sodium, and it's not complete sodium replacement either, just as it's not complete fluid replacement. So you know, you're starting at only about 20% sodium replacement, going up to maybe a maximum of about 70%, something like that. So obviously that range changes. The more aggressively you replace the fluid and the saltier your sweat is, the higher that percentage of sodium that you need to replace increases. And there's a nice little table in the paper that kind of illustrates all of that. Yeah, it's kind of hard to read out the table, yeah, in a podcast format, but, um, yeah, it's basically a mathematical equation and you can get some answers from it yep, and I'll link to that in the show notes so we can check it out.

Speaker 1:

now a couple questions here, because we talked about the fluid assessment looking how much do we lose? What do you advise on a sodium test in the way of a sweat analysis test? So if, if I I'm a salty sweater and I just say that without testing myself because I see salt rings on my kit and things like this would there be a situation where I'm doing hard three-hour road rides but I'm losing so much sodium that I need to replace it? So first, should we be having our athletes test our sodium concentration in our sweat? How best to do that? And does your model still kind of work out once we identify like a sweat or a sodium rate loss compared to fluid loss?

Speaker 2:

Yeah, so working backwards? Yes, the model does account for that. You can plug in different sweat sodium concentrations and then it'll give you different answers depending on that. Yeah, I guess the key thing in getting to your point and I guess it's the traditional thinking around sodium is I lose a certain amount per hour, I'm going to get a big sodium deficit. If I don't replace that, something bad's going to happen. That's kind of the traditional thinking about it and I guess it's thinking about it maybe in the same way that we think about glycogen, like our store of carbohydrate we use a certain amount and we need to replace it or we're going to run out, kind of thing.

Speaker 2:

What we know with sodium is that that's probably not so much the issue. The issue is balancing the water ins and outs with the sodium ins and outs. So we don't have any scientific evidence that you can develop a sodium deficit just in terms of the total amount of sodium in your body that is so big that something terrible, catastrophic is going to happen or performance will be impaired. There's just there is literally no evidence of that occurring. I think the amount of sodium you could lose theoretically over like a multi-day event, maybe that would occur, but then you'd be needing you know you'd die of dehydration before you die of lack of salt, unless you replace the water, in which case you need the sodium to balance the water that you're replacing anyway.

Speaker 2:

So I think it becomes a bit of a moot point. So no, it's very much, you know. You look at all the different possible scenarios. You know, could this happen, could this go wrong? Is it a three-day event or a three-minute event? And basically what you come back to is that the sodium is. You know, in terms of why would you do a sweat test is to quantify the losses, to work out. Do I need to replace, to balance the fluid ins and outs?

Speaker 1:

can we talk a little bit about pre-exercise sodium loading, if we want to call it that, and how that applies to any like performance training for high intensity, long durations and things like that, and in particular, maybe how sodium is governed between, like, the kidneys and the, the sweat glands when it like not during exercise? I think is the best way to kind of frame up that question, which is kind of a jumbled mess. But yeah, pre-pre-exercise sodium intake what are your thoughts on it?

Speaker 2:

yeah, I think there's. There's two lines of thinking that athletes can take around. This one and this is what I sort of tried to investigate during my phd was that your athletes will go out and get a sweat sodium test. They'll go oh my god, I'm a massively salty sweater. So therefore I need to quote unquote load up on sodium before my event. Again, that comes back to that thinking that I lose a lot of sodium. I'm going to rack up this big deficit in the total sodium in my body and if I, if that deficit becomes too large, something terrible is going to happen. As I said, there's no evidence that that is the case. Um, so what? What we were looking at specifically was you know, you go all the way back to World War II. There's, there's evidence that when you change someone's sodium intake, the sweat glands adapt to that, and so if you suddenly do that, I'm going to load up on sodium three days before the event because I had, you know, a high sweat sodium test Are you simply going to make the sweat sodium loss even greater during the event? You're kind of chasing your tail, in a sense. Sodium loss even greater during the event. You're kind of chasing your tail, in a sense um and so. So we looked at that and looked at a three-day intervention and basically doubled people's sodium intake. And yes, you do increase the sweat sodium loss during exercise because you load it up in the days before, because your sweat glands your sweat glands respond to that, just like your kidneys do. But the difference wasn't as big as we might have expected. It wasn't massive, but I still don't personally see the need to do that.

Speaker 2:

Now, the second reason that you might sort of quote-unquote sodium load before an event is more about the fluid side of things. So it's about taking a large amount of fluid in the hours before exercise, typically sort of two to four hours before exercise, and you're trying to retain that water so you don't just pee it out again. So why would you do this? This is usually for events that are long enough that you're going to become dehydrated if you don't drink anything. But they're events for whatever reason it's not practical to drink maybe gut tolerance, because it's so intense you can't drink it.

Speaker 2:

Um, logistically you can't get access to enough fluid during the race, or it's super hot that I'm just sweating so much that I'm never going to be able to drink enough to actually replace that. So basically where dehydration during the exercise itself is almost inevitable. So I want to get a head start and actually end up sort of starting with more water in the body, being a little bit hyper hydrated, as we call it, before you start exercise. And so this has been used in some events probably not so much in cycling. From my experience it's been more things like Olympic distance triathlon and road marathons in hot weather. So like the Tokyo Olympics was a classic example of that, but I haven't typically seen it around cycling events very much, because there's not many events that kind of sit in that sweet spot where you're likely to be faced with that scenario yeah, I would say from the my coaching practice standpoint um mountain bike races uh in particular.

Speaker 1:

So that's like the 90 minutes all out, technical, can't drink as much. I use it quite a bit there and and some of the products are like the um, um, the Osmo, preload, the scratch, hyperhydration, these types of things that I think the genre is about 1500 milligrams of electrolytes, primarily sodium, um, dumping it in you know an hour or two before and going for it technical hard crits that are hot and even you know road races or circuit races that are you know less than four hours. I've been experimenting with my athletes in the way of you know, like you said, it all comes back to the fluid right, we talked about in part one fluid is the number one sort of thing, but sodium can be a driver in that mechanism to kind of like preload, pre, and that preload is not just electrolytes, it's actually preloading fluid as well, and I I've been using that with with good success, um, I guess another product out there that's a little bit newer but it's also old. We made a nod to it as sodium bicarbonate, um, taking that uh before, and there's some buffering components to it.

Speaker 1:

I don't know if you want to talk about that, but I think the extreme amount of sodium in something like the Morton bicarb product can range anywhere between you know, 2.5 grams to six grams that you're pumping into your body, which I mean, let's face it, that's a, that's a shit ton of of sodium. And when I've done it personally, I mean I just I get really thirsty. I get good results from it varying results from it, I should say, but overall it makes me drink more and I think that that is probably one of the key benefits of it. Do you want to speak to sodium bicarbonate or anything else on sodium preloading?

Speaker 2:

Yeah, as you said, the bicarbonate side of it is more around the buffering side of things. I think that's probably a topic for another day. But you're right. I mean, obviously, if you're doing it with sodium bicarbonate, a lot of sodium is going to come along for the ride and that's going to have that effect of, you know, making you super thirsty. It's going to increase the osmolality in your blood. That's going to signal to out and then you you want to drink more.

Speaker 2:

I guess a potential downside to a couple of downsides to that one is if you don't drink the fluid with that, you can get a lot of gut issues because you're pumping all of that sodium bicarb into your gut.

Speaker 2:

It's actually going to draw water into your gut in the reverse direction. So that's not helpful unless you drink the volume of fluid with it. The second thing is, if you are feeling really thirsty and you didn't take that fluid with you, there is a risk that that actually impairs your performance because you're so preoccupied by this insatiable thirst that you actually don't perform well. So that is, I guess, where you might be playing with fire a little bit, and we see that with glycerol as well, which is the other agent that you can use instead of sodium to achieve the same effect. I've had a lot of athletes that have tried that over the years and and said, you know, I just felt terrible because I was just so thirsty the whole time and it's like, well, that's kind of the point, like right, it's again. It's it's about the balance between the water and the osmotic agent. Whether it's glycerol, whether it's sodium, it either means you just took too much of that for what you needed or you didn't drink enough water.

Speaker 1:

Um yeah, when I've when I've done some interventions like those with athletes I would also say most of them are shorter events like the cross-country mountain bike race or something like that I'll say the observation is, the athlete is also thirsty all day, kind of thing. It's just like an afternoon, like if they race in the morning, it's like an afternoon of drinking positive fluids. That is so. Um, I I should note I mean any. I would imagine that there's some uh considerations here, like if we have listeners who have hypertension or some history of that, probably uh stay away from any uh sodium loading right yeah, yeah, absolutely, and we don't really have good, good research in that, but, um, yeah, you probably wouldn't want to go mucking around with that kind of thing.

Speaker 2:

Yeah, yeah, so that's that is.

Speaker 1:

That is the, the warning there. Um, so we talked about kind of sweat testing, but really it's all about the fluid balance sort of things. Um, and to kind of bring part two uh to a to a close here and and try some summary points, to you I'd say that fluid is is kind of number one, but sodium they do go hand in hand. So don't think that we're saying fluid only. There's a lot of sodium that comes in the way of drinking and eating. That kind of balances this out for the sodium needs. But really there is a delineation of duration or extreme environment. That is kind of around that four hours of exercise intensity or a five liter loss where Dr McCubbin identified that sweet spot of, if you're replacing that, 60 to 80% of fluid loss. That's really where the sodium intake during exercise becomes vital. So that's kind of the first takeaway point. What else would you want to add to that, dr McCubbin?

Speaker 2:

Yeah, I think that delineation is as you said. You know you use the term vital there. I guess it's where I would say quantified. That's where you need to start thinking about testing your sodium losses and purposely replacing a specific amount of that, whereas below that your choice of sodium is more around driving that drinking behaviour, what tastes good to you and that side of things. So that's kind of what we call sort of season to taste versus sort of testing and targeting at that upper end. Yeah, that's probably how I would kind of distinguish between the two.

Speaker 1:

Perfect. So kind of point number two in part one of the podcast we talked about the fluid assessment test and in part two we talked about like the sweat composition testing identified that the fluid assessment is more important, the sweat testing, the composition of it, not as vital. But we really want to encourage you that if you've had some issues, um, with fueling and hydration in the past, do that fluid assessment. Now, dr McCubbin, question to you and add to this is uh, if people don't have issues in their training and racing, do they need to do the fluid assessment? Would you encourage them to go do it anyway, just for awareness and education? Or say, ah, no issues, no problem.

Speaker 2:

I probably would, especially if you're going to then go and do a type of event that you're not so familiar with. You haven't done it maybe so much before, or you're going to do it in conditions that you're not familiar with, either very hot or very cold compared to where you live, what you normally train in. I think they would be probably the main times I would do it. I think the only thing I'd add as a potential thing to think about here and I've seen this all the time with carbohydrate, maybe less so with fluid, but it is potentially relevant here as well is I've had a lot of people say to me know, I've talked a bunch of triathletes, you know all the way up to olympic level and sort of saying, well, how much carbs are you taking during your training session. They say, oh, you know, I have this, this and this and I go well, that's not very much. And they're like it's fine. And look, I'm training fine. And I say, okay, that's cool. You, you feel, okay, you're not, there's no issue, unquote. But just go out and maybe try what's recommended. That might be double in some cases the carbs that you're taking at the moment in training. Just do it for two weeks, there's no harm in it, and just see what happens at the end of the two weeks. If it makes no difference to your training, cool, I don't care, just go back to what you're doing before. It's no skin off my nose. They go and do it and they're like oh, I didn't realize I could do those kind of intervals in that session, like there was this extra level of performance that I didn't realize that they could get to because they hadn't tried it. So there wasn't quote unquote a problem or an issue that they had to resolve.

Speaker 2:

And I think with nutrition and hydration, often we don't tend to start thinking about it until there's a problem. And then we're trying to solve a problem. But we can go to the other end of the continuum, which is optimization, which is not necessarily fixing a problem. It's maybe can we get even better again. And so, again, from a fluid point of view, it's worth having a look at that, because maybe you are losing two and a half 3% of your body mass loss through fluid. You may be not feeling terribly thirsty, you may not be feeling like it's impacting on your performance, but you never know, maybe if you do drink a little bit more aggressively. Maybe you need some sodium with that or not, depending on the scenario. Maybe you will feel a bit better, perform a bit better and you might unlock, you know, even if it's an extra 10, 20 watts, that could be significant yeah.

Speaker 1:

Yeah, I fully agree with that. I mean, exercise physiology is a pretty young science in that way, and these little sectors of you know hydration and fueling and and tech and all this kind of stuff. I mean it's it's evolving too, and I, I would say the the endurance athlete that wants performance, you should evolve with the science. And just because it's not broken doesn't mean that you have to fix it. Sometimes it's optimization or just exploring new ways of doing it That'll make you feel better. And I would say, even if you are feeling better and you know it only increases in a little bit of speed and a little bit of power, it's not a bad thing, because there's a lot of health that can go on with that too, um, over the long haul. While you're doing these silly, you know endurance, ultra endurance, things. So, yeah, yeah, well, dr McCubbin, this has been awesome. I mean, I've taken all of your time in the world today, but, uh, I really appreciate it because our audience is going to soak in um so much from your wealth of knowledge.

Speaker 1:

And I want to make mention again to your podcast. It's called Fueling Endurance, right? Yep, that's the one. I'll link to that in the show notes. People can just search for it wherever they get their podcasts. But there I mean, what kind of genre of things are you talking about? Is it everything that we talked about here? I mean, do you have guests? Come on, tell us a little bit more about that podcast.

Speaker 2:

Yeah, so Fueling Endurance, like a lot of podcasts, started off as a lockdown project during the pandemic, and the format of it is that each episode is basically a question and we answer that question, and so they're sort of the common nutrition questions that runners, cyclists and triathletes ask, and we do have guests involved. A lot of the episodes not all of them, but a lot of them have a part A and a part B. Part A is usually some sort of expert, so a researcher or practitioner, if it's a more practical kind of question, and then the part B is typically an athlete, or occasionally a coach as well, adding their sort of unique perspective on that as well, and so that can be everything from you know, why do I get gut issues during exercise to do any sweat test, through to things like I'm over gels and bars and drinks, what else is there, and sort of looking at more of the DIY side of things. So it's a bunch of both, I guess more the science-y kind of stuff and the practical logistical stuff, you know travel and all that kind of stuff as well. So yeah, it's a variety of stuff.

Speaker 2:

This year we've also rolled out a six-part podcast series.

Speaker 2:

The first one has been around ultra running.

Speaker 2:

The next one's going to be around road marathon.

Speaker 2:

We will get to a triathlon one after that and then probably a cycling one as well, where we've actually taken a guest athlete and followed them for 12 weeks preparing for a specific event, and then every couple of weeks we check in with them and basically work on different aspects of nutrition as they prepare for that event, and so we've had a whole bunch of listeners that have then followed along with that guest athlete and kind of implemented the same things that they were doing as they were preparing for events that were either the same event or other events around that time, which has been really cool to to sort of follow that athlete's journey along the way and all the different things that we've worked on, from gut training to sweat testing that we talked about today, to practicing their carb loading for the day before the event. Putting it all together into a plan, trying it and even discussing things like accommodation for events like that makes a massive difference to your nutrition preparation for an event as well. So so, yeah, it's been going for four-ish years now. We had a variety of guests cycling, running, triathlon a lot of fun.

Speaker 1:

And yeah, long will it continue? I think I think so. I listened to a few episodes leading up to this podcast and I thought it was fantastic. So for any of our listeners who likes what they hear here and like what they heard from Dr McCubbin, I would definitely suggest checking out Fueling Endurance, because you're going to get a lot from that. You're also on the socials Twitter or X and Instagram. You're Fueling Endurance there and Twitter you're Next Level Nut. Is that correct?

Speaker 2:

Yeah, so my private practice, which I don't do as much of these days, but still a little bit, is Next Level Nutrition, so it's kind of a truncated version of that. But yeah, instagram's probably, you know, the Fueling Endurance. Instagram account's probably the one that's the most active these days from the athlete point of view, and the Twitter or X account is probably more on my you know, with my researcher hat on. Looking at that side of things. There's still some stuff for athletes there and I do a bit of writing for Escape Collective as well, so that usually goes out through Twitter or X as well.

Speaker 1:

Yeah, perfect, perfect. Well, dr McGovern, thank you again so much for your time. Really appreciate you coming on the podcast. Yeah, no problem, it's a pleasure. All right, take care. Thanks for joining us on the Time Crunch Cyclist podcast. We hope you All right, take care. 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.

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