Gut Training for Endurance Athletes with Patrick Wilson

Gut Training for Endurance Athletes with Patrick Wilson

Listen as Patrick Wilson, one of the foremost experts on athlete gut disorder, discusses the reasoning behind the intestinal issues that plague athletes.

This week Dirk sat down with Registered Dietician Patrick Wilson to discuss the common gastrointestinal issues that plague endurance athletes. Together, Dirk and Patrick cover everything from beverage osmolality, leaky gut syndrome, the benefits of periodic fasting and why more women are vexed with bloating and constipation during competition than men. They also cover which kinds of sugars are easiest to digest during exercise as well as the gut reactions pre-race anxiety can impose.

Patrick offers expert insight on all things related to athlete stomach distress and serves up fascinating, easy-to-implement advice for all endurance coaches and athletes.

Stand-Out Quotes

  • “When you’re looking to facilitate the fastest absorption as possible, you probably don’t want something super, super concentrated in terms of a beverage. So you want maybe something a little bit closer to your blood in terms of osmolality. We usually call that isotonic.”
  • “Distribution of blood flow changes pretty dramatically, depending on the exercise intensity… when you get up to like, 90% VO2 your muscles just require so much blood flow and so much oxygen delivery that something’s going to take a hit. And that’s something generally is the gut.”
  • “I think there’s some potential benefits for endurance athletes to do periodic fasted training… But I wouldn’t be overly concerned about it, so long as during the week you are practicing fueling during some of your training sessions.”
  • “Physiologically there’s some research to suggest that older people are less sensitive to catecholamines, those stress hormones.”
  • “Undoubtedly electrolyte beverages with carbohydrates have been shown to extend performance in some circumstances or improved performance, but the studies that have just given people sodium tablets or capsules, for the most part, they have not shown any benefits to performance itself.”

Resources

Patrick Wilson’s Twitter

Buy The Athlete’s Gut

Episode Transcript

Dirk Friel:

My guest today is Patrick Wilson who is a registered dietician and Assistant Professor of Exercise Science at Old Dominion University. He specializes in the relationship between gastrointestinal issues, diet, nutrition, and exercise. He is also the director of Old Dominion University Human Performance Lab, and wrote a book called Athlete’s Gut: The inside science of digestion, nutrition, and stomach distress. 

I highly recommend reading this book and using it as a reference guide for athletes who experienced stomach problems that affect their racing, which might actually be almost all athletes, I suspect. I hope you enjoy the show and gain a few useful tips you can apply to your training and racing. 

Patrick, thank you so much for joining me today.

Patrick Wilson:

Yeah. Thanks for the invite, Dirk. I’m glad to be here looking forward to talk[ing] about the gut. It’s always something that can be fun and sometimes a little bit gross to talk about, depending on what direction you go in.

Dirk Friel:

Funny, because we actually don’t talk about it enough and you know, I mean, as an athlete myself, it’s so funny cause we talked so much about training the muscles and strength training and the aerobic side of things and all the intervals we do and all the time spent in the pool and the running or whatever it might be. But then there’s actually very little devoted time if you will, to the gut or those discussions. But yet it is one of the biggest obstacles athletes have to overcome. I mean, you’ve seen that obviously in ultra running, a lot of the researchers showed, is that not the number one reason for DNF’ing ultra running events?

Patrick Wilson:

Yeah. The importance of the gut specifically like during competition or before competition is definitely going to vary between sports, but ultrarunning is definitely one of those worlds where it’s hugely impactful because obviously a big part of success for any ultra runner is being able to fuel during the competition itself, just because the duration is so long in the field demands are so high. You’ll see various estimates of how common, severe gut distress is in different events. 

But you know, some of the better surveys like done at the Western States Endurance Run, you see roughly, some years 40% of the runners saying that gastrointestinal distress is contributing to negative effects on their performance. If you look at dropouts, it is the single leading cause, it’s not the majority because there’s like 10 or 15 different causes for why people drop out of an ultra race, but of any one thing, it tends to top the list, at least in those surveys that were done at the Western States Endurance Run. 

So yeah, I mean it can be hugely impactful for some athletes. Now, if you’re doing something a lot shorter or in more skill-based sports, it’s probably less likely it’s going to completely ruin your performance, but it may still be bad enough that it has some negative effects, occasionally. Maybe not every single competition, but on occasion, almost every athlete is going to run into one of these problems eventually.

Dirk Friel:

Absolutely. Have you seen anything, any of these types of surveys or studies centered around, you know, Ironman?

Patrick Wilson:

There are some studies that have looked at the rates or the severity of gastrointestinal symptoms in Ironman. Off the top of my head, I don’t recall the exact numbers. Some of the difficulty with the research in this area is the symptoms that are asked about. Cause there’s probably anywhere in between seven and 10 symptoms, you could kind of ask about maybe a little bit more than that and not all surveys ask about all the same symptoms. And then how do you quantify the severity? 

You could ask on a zero to 10 scale, which I’ve done commonly for some of my studies and if someone reports are a one or two, you could still define them as having GI symptoms, but it wouldn’t necessarily be bad enough that it really impacts their performance, right? And even if they had like a rating of four or five, but it was for burping or for flatulence, it probably isn’t going to really hurt their performance in the end, right. Whereas a three or four for nausea, bloating cramping, that’s definitely more likely to be impactful. But as a rule of thumb, the longer the exercise duration goes, the more likely it is that an athlete is going to experience some major gastrointestinal malfunction during the course of an event. So Ironman would definitely be one of those races where it’s fairly common to have those types of problems.

Dirk Friel:

So if we get down to what is, I guess, reasoning for that? I was getting into the details of the book and it never really associated the blood flow and osmolality and how important that really is to gut function. Can you go into some of that for us? 

Patrick Wilson:

Sure. I mean, in terms of the duration, one of the reasons I think you see higher rates of GI symptoms, is kind of multiple fold. You’re more likely, maybe to have fluid imbalances over longer exercise durations, maybe larger amounts of dehydration in some cases. The other thing, especially with running events is just the repetitive impact over time. I mean, you’re talking about thousands and thousands of strides over the course of an ultra marathon. And as you progress further into that race, there’s more and more muscle damage that occurs. And some of those breakdown products that come from the muscle, specifically when it comes to nausea, which is a pretty prevalent symptom among ultra runners. And it’s one that tends to be really difficult to get rid of, or to deal with and it can hurt your race performance quite a bit. That’s one of the things in your blood that theoretically might trigger in your brain, this nausea center or vomiting center that contributes to feeling that you gotta throw up, whatever you just ate.

But there’s many things that increase in the blood over the course of exercise. You’ve got stress hormones, you’ve got hydration related hormones, like arginine vasopressin, and most of these hormones in large amounts are in higher amounts we know can contribute to nausea. 

So I think that’s one of the major reasons why you see such a high rate in ultra endurance running. And that’ll probably would include an Ironman, where at the end, you’re doing a full marathon after doing hours of exercise before that. You just kind of get this stew of stuff in your blood that can trigger nausea. Now the other symptoms, it kind of depends. It may be that your gut lining is starting to be damaged. The junctions that are kind of usually tight that hold the cells together in your intestines, start to loosen up. And it may cause a leakiness of things like bacteria and endotoxins that can make gastrointestinal symptoms worse. So it’s really probably a multitude of reasons why prolonged exercise is associated with more severe GI issues in most cases.

Dirk Friel:

Right? So you talked a lot about these endotoxins, bacteria being in the blood, the loose, leaky gut is what you’ve termed it. Definitely get that. What about in the gut itself? So in the stomach the osmolality, how important is the concentration of what you’re taking in and how does that relate to blood flow and possible problems?

Patrick Wilson:

Yeah, so beverage concentration and beverage osmolality, that does become important particularly like immediately before and during exercise itself. Now, post-exercise and pre-exercise, those are different scenarios. So when I’m talking about beverage osmolality and concentration, it really is most relevant to pay attention to when you’re selecting beverages to drink during an Ironman, during an ultra race, whatever it may be. 

And when you have a really concentrated beverage, either because it has a lot of carbohydrates, or it has a lot electrolytes like sodium or a combination of both, it can slow down emptying from the stomach a little bit, because one of the things that regulates how fast fluids will empty from your stomach is the beverage concentration and the osmolality. Once the beverage starts to get into the small intestine, if it’s very concentrated or again, it has a very high osmolality, what’ll typically happen is there’s going to be some fluid that comes from your blood and is pulled out into the intestinal lumen, the tube space to at least temporarily equate or get the osmolality is a little bit closer between luminal space in the blood space.

So that can cause in some people a cramping sensation, kind of a stomach ache. Maybe someone who’s downed like a soda or a really concentrated juice during a race, and the next 10 or 15 minutes, they kind of feel like they’ve got a little bit of a stomach ache. That may be part of the reason why, the beverage concentration in the osmolality is just too high. 

Now, eventually that beverage is going to get absorbed, but it may just take longer. So when you’re looking to facilitate the fastest absorption as possible, you probably don’t want something super, super concentrated in terms of a beverage. So you want maybe something a little bit closer to your blood in terms of osmolality. We usually call that isotonic. Hypertonic would be something that is a lot more concentrated in the blood and hypotonic would be something like water, that doesn’t have much at all in terms of electrolytes or carbohydrate, obviously. So that’s most important during exercise itself and it’s most relevant when we’re talking about large beverage volumes. 

If you’re just sipping on a hypertonic beverage, you may or may not have problems, but if that’s your main beverage source, like that’s all you’re drinking is a hypertonic beverage that is potentially a recipe for gut problems. So that’s just something to be aware of when picking a beverage during competition during training itself.

Dirk Friel:

Okay. So how about gels? I’m sure you’ve been asked about this a ton, a gel is obviously super concentrated, very little liquid within it. It’s 25 grams per shot, I believe for the most part of carbohydrate. What are any kind of rules of thumb around gels?

Patrick Wilson:

Yeah. Gels are interesting because obviously you can mix and match gels with whatever rate of fluid you want to consume. So scientifically speaking, it’s a little bit harder to separate all those different effects of the beverage volume versus the rate of gel ingestion. Different gels have different osmolarities, different gels have different types of carbohydrates. So that’s where it becomes a little bit problematic to give just like a simple rule of thumb with gels is because they do vary a lot from product to product. 

What I would say is because there are so many options out there you really need to practice with those specific products that you plan to use. And if you’re going to do something really aggressively, which would be anything more than like two gels an hour, then yeah, you definitely need to train yourself to handle that. And you may need to play around with different products and experiment to see, “okay, my gut seems to be able to handle this particular product for whatever reason.” Maybe it has more maltodextrin as the main glucose source. Whereas another gel maybe has more glucose and dextrose. I mean, there’s a variety of things that could contribute to tolerability with gels. So that’s a tough one to really have like just a simple rule of thumb. The only thing I could kind of come up with a simple rule of thumb is if you’re going to do more than two an hour, you really need to train with that at least for a couple of weeks before a competition.

Dirk Friel:

Okay. We’ll get into training the gut a little later on. If we continue on around factors that influence gut problems, you’ve talked a lot about the time factor, but the intensity side of it that it’s equally as important. I can go for a six-hour walk and eat a steak along the way. Right? So therefore it’s not simply time. It now becomes time at what intensity. And why does intensity place such a big factor on the gut symptoms, right?

Patrick Wilson:

Yeah. I mean, that’s a good example or a good way to put it is that, you know, extreme exercise duration can cause or contribute to GI symptoms, but that assumes you’re kind of giving a maximal effort, right? If you’re just walking for six hours, you could kind of eat whatever you want. For the most part, you’re probably going to be fine. 

So it is this interaction between intensity and duration. Naturally as events or competitions get longer, obviously the average intensity for those events are going to go down, so there’s that kind of inverse relationship between duration and intensity. So what we do see is that there are certain gut symptoms that are worse when you look at shorter, really high intensity bouts of exercise. So whether that be a tempo run, an all-out race-pace type thing, interval workouts, repeated sprints, nausea is definitely one of those that kind of tends to be more prevalent when you do really high intensity stuff, especially when you’re doing like repeated sprints. 

Anybody who’s been a 400 meter runner in track, you know the feeling of feeling nauseated after giving a full-out effort in a race like that or the 800 meters. The reason for that is a few fold. Distribution of blood flow changes pretty dramatically, depending on the exercise intensity. at modest exercise intensities say, 50% VO2 max, your gut blood flow is pretty well maintained. Your body generally has enough blood flow to distribute to both the muscle and the guts to be able to function appropriately. 

But when you get up to like, you know, 90% VO2 or something like that, your muscles just require so much blood flow and so much oxygen delivery that something’s going to take a hit. And that’s something generally is the gut. And that can contribute to symptoms is a lack of blood flow. Because when you have a lack of blood flow, you have a lack of oxygen delivery to the gut. And that can cause some level of dysfunction. 

The other reason is, as a byproduct of giving a really good effort, whether it be sprinting or interval workout, your body releases lots of stress hormones like adrenaline, noradrenaline and those hormones we know from other research act on the brain to trigger nausea in some people.

And that may be part of the reason why, if you, for example, take a lot of stimulants or caffeine before a real intense workout, sometimes people have more nausea because it’s exacerbating the stress hormone release. 

Same thing would be for fasting. Fasting tends to increase the release of adrenaline and noradrenaline if you’ve done it for more than eight to 10 hours. And if you pair that with intense exercise, nausea is more prevalent in people who were fasted in here doing something really intense, versus somebody who maybe ate a couple of hours ago. So yeah, it probably depends to some extent on the symptom that we’re talking about. Some symptoms that are going to be more prevalent with different exercise, intensities and durations, but nausea is one that tends to be common with both with both very short, high intensity stuff. And then also very super long stuff, but maybe for different reasons, right? The actual underlying causes can differ in those scenarios.

Dirk Friel:

Well, I have to bring it up. You mentioned fasting. I don’t know if a trend, but certainly athletes are doing fasted workouts in an attempt to raise their fat oxidation capabilities and I think you mentioned this possibly in the book, but by doing fasted workouts, does that not just inevitably train the gut to empty at a slower rate?

Patrick Wilson:

I think it depends on how often you’re doing it. I think if you do it once or twice a week during your moderate intensity workouts. So like for example, if you woke up in the morning decided you didn’t want to really eat before a moderate intensity workout and did that once or twice per week. And some of your other training runs, you are focusing on fueling, I don’t think it would be a big deal in terms of your gut’s function. 

But if you’re habitually doing fasted training almost all the time, or just in general, you’re not consuming enough energy in your diet. Like if you have what we call relative energy deficit, you’re just completely under fueling, that is probably going to be more problematic than periodically doing some fasted training. I mean, I think there’s some potential benefits for endurance athletes to do periodic fasted training. I think there’s still a lot of research that needs to be done to show how big of a benefit, in what situations, what’s the best way to implement those strategies. But I wouldn’t be overly concerned about it, so long as during the week you are practicing fueling during some of your training sessions. 

Dirk Friel:

Got it. You mentioned the book about age and training experience and how it gets better with age, why is that and what have you seen? 

Patrick Wilson:

We don’t have a clear answer, which one is more important. Is it more important that as people get older, there’s something physiologically going on, that’s reducing the severity or the incidence of some gut issues? Or is it just that, typically people who are older have been training for longer and are better able to kind of prevent or get a hold of some of the gut issues that they’ve experienced in the past?

And my guess is it’s probably a combination of both. So there’s studies where we look at the correlations and try to find things that predict GI symptoms. And honestly, the correlations are never very that strong and they’re usually pretty modest. And that’s because for any symptom, there’s probably going to be a multitude of factors that play a role, but consistently age is inversely correlated with the severity of the incidence of symptoms. So the older people get the less likely they are to develop symptoms.

Now, physiologically there’s some research to suggest that older people are less sensitive to catecholamines, those stress hormones, and those stress hormones are playing a role in, for example, blood flow changes that occur with exercise. So if they’re less sensitive to those stress hormones, or maybe they’re releasing less, then maybe they have less or smaller reductions in gut blood flow would be one theory. Potentially they’re just doing less intense training. They’re just getting more experienced. So through practice, through trial and error, they may have figured out, “Hey, maybe I shouldn’t be doing this before my runs or my cycling sessions or whatever else I’m doing.” But both experience and age are modestly correlated with the incidence and severity of GI symptoms during training and competition.

Dirk Friel:

All right, older, wiser, wisdom comes into play. What have you seen with males versus females in terms of GI issues’ prevalence?

Patrick Wilson:

Oh, certainly there are symptoms that are more prevalent or severe in women, and that would tend to be things like bloating and constipation. Occasionally you’ll see certain symptoms, more common in men, probably the most notable be something like heartburn. But overall, if you add up all the symptoms together and add the scores, if they were to rate all the symptoms on it, like zero to 10 scale, generally, there’d be a little bit higher in women. 

Now, the bloating and constipation, obviously that could be related to some extent to menstrual cycle changes. Those symptoms tend to, for example, bloating tend to be worse during different phases of the menstrual cycle. But it may also be because transit through the guts and the colon in particular tends to be a little bit slower in women. So if you’re, for example, eating lots of carbohydrates and fiber in your diet, once some of that fiber gets to the start of the large intestine for a female, it’s gonna take longer for that fiber to get to the end of the colon.

Now, what does matter is if the fiber sits in the colon for longer, that is more time for the bacteria there to break it down, to produce gas. And that’s one of the byproducts of fermenting fiber in the gut is going to be things like methane, hydrogen and carbon dioxide. Also, if that fiber is sitting in the colon longer, that’s more time for fluid to be reabsorbed, which would contribute to constipation. So that’s one of the explanations for why in women, you’re probably more likely to see both constipation and bloating are some of these differences in transit time. 

It’s just on average, there seems to be a slower transit of things, especially through the colon among women. And this is not just true among athletes. I recently published a study with data from the general population and probably the most consistent, or one of the most consistent predictors of constipation was just female gender. So yeah, it’s, there’s some differences between men and women, but on average women kind of tend to get more of it, unfortunately for them.

Dirk Friel:

So let’s get into some of the finer details of strategies. Talking about fueling, we touched on a bit. Osmolality for example, at a higher level, but when we actually start counting carbs, carbohydrate ingestion per hour, this 35 to 45 grams an hour for one to two hours, seems to be that happy place, right? Where, okay, you shouldn’t really expect too many problems here. Is there a reason for athletes to push beyond that level, going above 50 grams an hour?

Patrick Wilson:

I think the only athletes that really seriously need to consider that are those who are doing stuff that are, number one, pretty prolonged more than two to three hours. And then number two, we’re on the higher end of the spectrum in terms of their ability. They’re better athletes who are sustaining a higher percentage of their VO2 max.

Dirk Friel:

Okay,

Patrick Wilson:

So if you’re like a middle-of-the-pack or back-of-the-pack, even ultra runner and you’re going at 45% of your VO2 max for the whole race, you don’t need to be consuming 70 grams of carbohydrate per hour. Cause you’re not even probably burning that much, in terms of a carbohydrate fuel. If you’re not exercising at a fairly high intensity. 

So it depends on the duration of exercise and then the caliber of the athlete. So better athletes who are doing longer stuff, that’s a situation where you’d expect them to maybe benefit from a higher intake, somewhere between 60-90 grams per hour is typically where you see the recommendations. There have been a couple of studies recently that have suggested that theoretically, you could go up to 120. I’m a little bit skeptical that that’s gonna lead to better performance, but some athletes are even trying that at this point.

There was a recent study, I think Spanish trail runners…

Dirk Friel:


Was that Itor Virabe?

Patrick Wilson:

Yeah, I think they did three conditions. One was like the normal, one was like 60 grams… 60, 90, 120. So they were all pretty aggressive, right? That’s a lot of carbs to eat. So that’s your all kind of five to six gels an hour. 

So number one, you’d obviously need to train and do that a number of times before you ever consider implementing it in a race. And I’m not yet convinced that that will actually lead to any better performance. I mean, we’ll wait and see to see if there’s studies that come out, showing that it does, but I’m not yet ready to say that you need to go that crazy.

Dirk Friel:

Right. So we’ve seen or heard that Eliud Kipchoge, who set the sub-two hour marathon did do 100 or 200, 100 grams an hour. So that gets to the intensity side. Obviously he’s trying to set a world record. He’s at the very upper limit of that capability and obviously has been training for it within his training. So if we are going for… let’s say we are trying to podium or qualify, whatever it might be for Kona, Ironman, Hawaii, or whatever top level competition. If we are going to go for the 75 grams an hour, talk to me about the selection of that carbohydrate choice.

Patrick Smith:

So the research on this kind of pushing to the higher end of the spectrum and trying to be really aggressive about carbohydrate intake. I mean, there’s been studies over the last probably about 15 years. 

A lot of them were done, I think in Asker Jeukendrup’s lab and some of his colleagues where they would feed a cyclist in most cases, either a pure glucose beverage. And then in another condition, they would get basically the same amount of carbohydrate per hour, but a mixture of glucose and fructose. So the study varied in the ratios of how much glucose or fructose, but anywhere from two to one to 50-50 have kind of been the typical ratios. And generally what you see is that, more of that ingested carbohydrate gets burned for energy when you consume a mixture of glucose and fructose, but that really only happens if you’re consuming more than like 50 to 60 grams per hour.

And that’s because when you get at that level, the transporters in the intestine that absorb glucose and fructose get saturated, if you’re going above, 45, 50 grams an hour, so that’s kind of the limit for both of those sugars is about 45 to 50 grams an hour. If you add them together, that’s about 90 to 100 grams an hour is what you could probably handle with those two sugars. So if you instead try to consume like 90 to a hundred grams per hour of just glucose, or even like maltodextrin or any other source of carbohydrate, that is a chain of glucose, it’s unlikely that all that is going to be absorbed. 

And the problem with that is when an unabsorbed carbohydrate sits in the gut, it causes problems. Fluid gets pulled out into that space to again, equate the osmolality. Once that glucose gets down into the colon and the distal small intestine, it’s going to get fermented by bacteria, that’s going to cause bloating and gas. So you think of the combination of symptoms of loose stools, or just to go number two, bloating and gas not generally going to be great for performance. 

So if you want to push the boundaries of your performance and you’re doing something more prolonged, probably at least a full marathon distance and beyond, and you’re going to consume more than 60, 70 grams, an hour of carbohydrates, you definitely want to probably go with a mixture of glucose and fructose, would be the number one recommendation. Maybe including some maltodextrin as the source of glucose, cause that can, in some cases, have an effect on gastric emptying and maybe is emptied from the stomach a little bit more quickly if you just pick something with dextrose or glucose in it. So there’s some other little things you can do, in terms of beverage or product choice, but the number one thing I would say is make sure you get a mixture of glucose and fructose.

Dirk Friel:

Right. And the underlying reason for that is because they have different receptors that they attach to get absorbed. And have you seen any studies where you are just born with the number of receptors or is that part of the experience of training? Can actually training the gut increase the number of receptors? Therefore you can improve your capability over time?

Patrick Wilson:

Yeah. The animal studies that we have say that yes, you can increase some of these transporters in that directly shown in humans, as far as I’m aware, partly just because you’d have to take samples like biopsies and the small intestine, which is not an easy thing to do, but there are, there’s indirect evidence to suggest that this may also be happening in humans. 

One study looked at a training, the gut protocol over, I think it was four weeks. One group got extra carbohydrates. The other group got extra fat in their diet. And after this kind of four week of training, the gut to handle more carbohydrate, the group that got the extra carbohydrates were burning more of the ingested carbohydrates, they kind of use these special forms of glucose that you can trace in the body. And they showed that more was being burned. Now you can’t say whether it was because of better absorption or better entry into the muscle or something going inside the muscle itself. But the suggestion is that it’s probably having to do with the rate of absorption in the gut. So there’s some indirect evidence to say that this also happens in humans.

Dirk Friel: 

Got it. So on the hydration side of things, there’s been studies to show, drink to thirst, obviously a lot of athletes stick to a schedule as well. How would you go about advising folks around hydration? And there’s no one rule here obviously, because of the weather. It could be 50 degrees or 95 degrees. So is it always just drink to thirst?

Patrick Smith:

I tend to not be in that camp of, it’s always drink-to-thirst. To me, it’s drink-to-thirst, if it’s less than two hours, I would say is probably a pretty good rule of thumb in my mind. The duration of the event, typically isn’t long enough for you to accrue such a large fluid deficit that it’s going to impact your performance negatively. There might be some exceptions to that, like in a really hot and humid environment, or if an athlete starts out a little bit dehydrated, then drinking to thirst may not actually be the ideal for that shorter type of event. But I think in most cases, drinking-to-thirst is probably going to be somewhat adequate in those shorter events. 

The other reason why you might not want to go too aggressive with drinking those shorter events, is if you’re trying to replace most of your sweat losses because those events are shorter, the intensity is naturally higher in sweat rates are typically higher. And if you have an athlete who’s sweating, let’s say one and a half liters an hour replacing even two thirds of that can be pretty challenging. I mean, replacing all of it is going to be a recipe for gut distress. I mean, try drinking a liter and a half of fluid per hour while you’re exercising. It’s not going to go particularly well for most people. Right?

So for longer events, my suggestion would probably be to at least get an idea about your sweat rate in different environmental conditions. So throughout the year on different days where there’s different temperatures go out for an hour at your race pace, see what your sweat rate is based on how much body mass you’re losing in that hour. And there’s online calculators people can use if they don’t know how to do this, it’s not too complicated just to get a sense of, “okay, how much am I actually losing at this pace in this environment,” roughly speaking so that if you want to do something more regimented, you at least have somewhere to start. And I would not say replace 100% of what you lose, but maybe half to three quarters, depending on the situation would be maybe a rule of thumb. For me, it just depends a lot on the environment and the length of the race, your opportunities to drink, what fluid sources you’re going to be bringing with you all sorts of stuff.

Dirk Friel:

Yeah. I’ve certainly done a lot of hot races in my time and when I think about sodium replacement, I don’t know why, but I always gravitated towards sodium during was like number one, you know, take more sodium in during the event. That’s where I think most people tend to gravitate towards when they think of hot conditions. And then secondarily it’s post race or training obviously. So a really hot training session, get it back in right afterwards. But, I never actually got to the point where I was thinking about pre-exercise pre-race, sodium intake as a strategy. So if we could walk through each of those, talk to us about sodium replacement supplements during a hot event.

Patrick Wilson:

Sure. You kind of hit the nail on the head there with different dynamics with before, during and afterwards. So there’s this concept of fluid loading that’s been around for awhile. And originally, I think most of the studies looked at using glycerol, which is a three carbon molecule, you can ingest, the osmolality of that allows you to hold onto more fluid in your blood. So there have been studies that have asked people to load with glycerol and you see that they have higher plasma volumes. For example, when they do that, a few hours before exercise with the idea that you’re going to be sort of hyper hydrated, going into a hot and hid environment. And there are some studies suggesting that that may actually help performance in a hot and hid environment.

Now, the issue with glycerol historically, was that it was banned by WADA because it could be used as a masking agent for other banned substances, where recently, I believe, they took it off the banned substance list. So I think theoretically, any athlete could use glycerol if they want, but in the interim, there was more interest in using sodium as a similar hyper hydrating agent because the more sodium you kind of have in your blood in general, you may be able to hold on to more. That’s part of the rationale for people adding extra sodium to their post-exercise beverages, is it helps you kind of hold onto more of the fluid you ingest. So for example, if you ingested one liter of water versus one liter of sodium rich beverage over the next four hours, you’re going to pee out more of that pure water because there’s less sodium in it.

So there’s been a couple of studies, Stacy Sims has done a couple of them. She did one with men, one with women where she had them hyper hydrate with a very sodium rich beverage, I think starting a couple hours or 90 minutes before exercise in a hot environment and found that they were able to go a little bit longer in a hot environment when they hyper hydrated with a sodium rich beverage, with the idea that maybe you just delay when a significant level of dehydration occurs. It just takes a little bit longer to get there because you start off with more fluid that you’ve held onto. The caveat to those research studies would be that most of them did not allow people to drink much during the exercise itself. So I don’t know about the generalizability of that to an IRONMAN.

That’s a little bit harder to say so, and they could try that, if they’re anticipating that they’re going to sweat a lot and they may have limited access to fluid during the event, you know, hyper hydrating with a sodiu- rich beverage, or even a glycerol-rich beverage something they can consider. Now during, there have been a handful of studies that have tried to isolate, does sodium itself do anything for performance.

Now, undoubtedly electrolyte beverages with carbohydrates have been shown to extend performance in some circumstances or improved performance, but the studies that have just given people sodium tablets or capsules, for the most part, they have not shown any benefits to performance itself. In some cases you see some differences with perceptions of thirst and drinking rates and the amount of fluid that people retain. But for whatever reason, those perceptual and physiological differences have not transferred to a performance benefit in the studies that have been done.

Now, most of those studies have not been super long. There’ve been a couple that have done it, I think with a half iron, an iron man triathletes. So I’m not ready to say that it’s useless to consume sodium during exercise. I think in longer events, it makes more sense to do some of that. But to be honest, I think for most athletes, they don’t need to focus hugely on the sodium during the event itself. I think it’s probably more of a priority post-exercise and throughout the day to make sure that you’re getting adequate sodium, because an athlete will lose a lot of sodium. If they’re exercising for 10 hours in sweating, you know, one to two liters an hour, you do need to replace that, but it doesn’t necessarily have to be during exercise itself.

Dirk Friel:

Got it. Yeah. Certainly a lot of athletes just assume [they] gotta take in supplements when it’s hot and that certainly can also lead to cramping or other issues if taking in too much. So keep that in mind. What I love about the book is that you can isolate these problems in a way, like there’s so many different possible reasons for all these different symptoms. And I think you have 10 or 12 different symptoms that you might have from gut issues. But what might be the reason for them. And then the strategies to alleviate them are just so mixed. There’s no one source. 

You also get into obviously the psychological side of racing and training and how that affects gut issues, stress and anxiety. And you mention, some NFL, NBA players that obviously have documented problems around anxiety disorders and how they get nausea and have to vomit almost between or before every single game. So, I think it’s great that you brought up the psychology side of things. What were your findings there and maybe possible ways to go about alleviating some of those issues and especially pre race anxiety?

Patrick Smith:

So it’s been an underappreciated factor in gut problems, in athletes, at least from a research perspective. I mean, there’s lots of anecdotes of recreational and professional athletes experiencing gut issues, nausea, vomiting before competition because of how stressed and anxious they are. So, the anecdotes I give the book, Bill Russell supposedly vomited before many of his really big basketball games. He’s an offensive guard from the Philadelphia Eagles. 

Brandon Brooks who has been hospitalized, has missed a lot of games in some cases because he’s had an anxiety disorder that contributes to nausea and vomiting which, he admitted to and told, even though with football, it’s kind of a tough man’s sport. And I think that’s gotta be pretty tough to tell the world that that’s an issue you’re dealing with in a sport that kind of has that mentality.

But for endurance athletes, I’ve done a couple of studies now in the last few years, simply simply looking at the correlations between levels of anxiety and stress and the incidence and severity of these gut problems. Probably the most relevant one we just published in the last half year, I think, where we ask people to report their general levels of anxiety habitually, like how do you typically feel? And then on the morning of a race. And the race, it could be a triathlon, running so long as it’s 60 minutes or longer. And those athletes who reported the highest levels of anxiety on the morning of the race, in comparison to those who had lower levels of anxiety, had about five times the odds of experiencing substantial nausea as one example. 

So definitely these links exist in athletes.We’re starting to document that now more and more with research. The question is, what can we do about, or practically to get a handle on this? This is where it starts to get a little bit speculative. I’ve got a PhD student who is hoping to do some research this year to address this actually with an intervention. But what you might try as an athlete at this point, is going to be something like slow, deep breathing, mindfulness, cognitive behavior therapy, maybe relaxing music. So anything that really activates the parasympathetic branch of your nervous system, because what happens probably, for a lot of these athletes who are overly stressed or anxious, is that they’ve just got too much sympathetic, nervous system activity going on. And anything that can kind of calm you down and activate that parasympathetic branch of the autonomic nervous system, in theory, could help with some of these gut issues. 

Now, this has not been shown in athletes, but there are some studies in other populations that seem to confirm that this is likely to have some benefit. We just need to show it experimentally in athletes to really say for sure, but there’s a pretty low risk to doing these things, right? I mean breathing, I can’t really think of much of a risk to doing that.

Dirk Friel:

A little yoga, a little meditation in the morning, 4:00 AM before the Ironman can only help. So, you know, starting to wrap up here, how about some general thoughts around working gut training into your training program? Are we talking about three days a week, every day? Is it just the long sessions? How much time should we put into the actual race day simulation as it relates to nutrition and just training the gut?

Patrick Wilson:

Really good question. I think the amount of time and effort you put into it is proportional to how aggressive you’re going to be on race day. To be honest, if you’re going to be someone who’s really trying to hydrate and keep up with your sweat rates pretty closely, if you are someone who’s going to be consuming more than 60 grams of carbohydrate per hour, then yes. Especially leading up to that race, within two to three weeks beforehand, probably at a minimum, you want to probably do this a couple of times for a week, just to see how it goes to fine tune things.

For someone who’s a middle-of-the-pack or triathlete, who’s not as aggressive about their per hour fluid and food intake, then practice it a few times leading up to the race. And if everything feels okay, then I think that’s probably going to be adequate for a lot of athletes. But the problem is, it’s hard to simulate what happens after 10 hours, right? Once you’ve dehydrated in a hot and cold environment during a race, that’s a hard thing to simulate.

Dirk Friel:

Yeah. Most people don’t do a full Ironman in training and obviously, it’s not all that recommended, so it can be tough to actually simulate those race day conditions.

Patrick Wilson:

Exactly. So you can only do so much. But that’s my thought on it is, if you’re going to be more aggressive about your nutritional intake, in terms of fluid and carbohydrate per hour rate, then you need to spend more time on it to make sure that it’s not going to be a disaster on race day.

Dirk Friel:

Right. Well also, there’s differences in sport types. If you think of a cyclist that might race 20 times a year, they have a B and C races and they might have more C races obviously than B races. So they have more time to experiment actually within racing itself. Ironman athletes, 70.3, tend to race very few times per year. So it’s just a matter the magnitude of the possibilities, just of things that could go wrong, in that you haven’t had the chance to experiment, but there comes in the wisdom, the experience of being an athlete and having the years under your belt and knowing what works for you

Patrick Wilson:

There is something to that understanding, that if something goes wrong during a race, you know, obviously if it’s like the Olympics and you’re going for a medal, that’s hard to swallow, but if it’s a race that isn’t for a championship or something like that, just take and learn from it because it’s an experience that you can use to improve the next time you go out on the course. And that’s definitely true of kind of the nutrition plan and nutrition strategy.

Dirk Friel:

Yup. Well, I thank you so much, Patrick, so much covered in the book. I think it’s a great reference book, so much in there that can last an entire career. And now you are presenting at our Endurance Coaching Summit in November, correct? 

Patrick Wilson:

That is correct. Yeah. I’m looking forward to that. 

Dirk Friel:

Just so everybody knows, that’s November 17-19 go to summit.trainingpeaks.com to sign up. And lastly, Patrick, how can people maybe follow you or contact you if they have more questions?

Patrick Wilson:

Yeah, probably in terms of social media stuff that I use professionally is going to be Twitter. And if they want to follow me, my handles @sportsRD_PHD

Dirk Friel:

And the book, does the book have a website?

Patrick Wilson:

It does. Yeah. They can go to theathletesgut.com as well. And they can find

Reviews and you can download like a sample chapter or sample section of the textbook. If you want to give it a little preview, check out a few other things as well. 

Dirk Friel:

Awesome. I learned a whole lot, whole lot more for me to learn and experiment with. So I appreciate all the advice. And thank you so much. 

Patrick Wilson:

Thanks Dirk. It’s been a pleasure talking to you.

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