Episode 16 - 7 Nutrition Tips for Exercising in the Heat

7 Nutrition Tips for Exercising in the Heat

It is getting HOT down under! Training and racing in summer can be challenging. But there are some nutrition strategies that can help you manage the heat. 

In this episode, I want to set you up for success in a hot environment. I discuss what actually happens to the body when we exercise in the heat and give you 7 practical strategies to manage exercising in hot environments.

If you’re interested in understanding your personal hydration needs, book in for Sweat Testing with an Advanced Sports Dietitian today!

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Episode Transcription

Episode 16 - 7 Nutrition Tips for Exercising in the Heat

Welcome to the Triathlon Nutrition Academy podcast, the show designed to serve you up evidence-based sports nutrition advice from the experts. Hi, I'm your host Taryn, Accredited Practicing Dietitian, Advanced Sports Dietitian, and founder of Dietitian Approved. Listen as I break down the latest evidence to give you practical, easy to digest strategies to train hard, recover faster and perform at your best. You have so much potential, and I want to help you unlock that with the power of nutrition. Let's get into it.

Down under here in the Southern Hemisphere, it is getting HOT. Training in our Aussie summer can be really challenging for some. Maybe not as challenging as one of my clients Sas who is from Kuwait, and trains regularly in 40 degrees. But still, it's hot. So, what I want to do with this episode is give you some useful strategies for exercising in our hot summer months. If you're listening in from the Northern Hemisphere, and you're heading into winter, maybe come back to this episode in six months when you're heading into your summer.

But I want you to set yourself up for success. Because it is really hard to exercise in the heat. I'm sure you've experienced it. One of the biggest impacts of heat exposure, when we're exercising, is its effect on the gut and that's exacerbated when our core temp gets greater than about 39 degrees Celsius. So, some of the nutritional strategies that I'm going to walk you through today, are to help you keep your core temp below 39 degrees. We'll talk through what they are.

Before I get into that practical stuff, what actually happens to our gut in the heat? I think it's important we take a step back and understand that first. So, your strategies are set up to minimise the impact of what happens.


What happens to the gastrointestinal tract (GIT)?

So let's set the scene. What actually happens to your gastrointestinal tract when we exercise? The main thing is the redistribution of blood flow away from our gut. It goes towards our working muscles, where we want it and all of our peripheral circulation to cool you down. That results in decreased perfusion, low blood flow, to our organs in our abdominal cavity. That causes gut ischemia or lack of oxygen.

Plus, when we exercise, we have sympathetic activation, which is our fight or flight response. Because you don't want to spend energy digesting food, when you're trying to run away from a lion. We also have suppressed gastric emptying. So we're less efficient compared to normal at emptying our stomach and having food moving further along the digestive tract where we want it to go. Our digestion and absorption are suppressed as well. So all of these things happen with exercise. Our body is just working against us digesting because when we're trying to run away from a lion, we don't want to waste energy digesting food. We just shut all that down. The longer and more intense the exercise, the worse it is. So think Ironman. It's like tick, tick, tick. All of those components are exacerbated by heat exposure. So what works for you in a cold environment may not work for you in the heat.

Also in the heat, we rely much more heavily on our muscle glycogen. So we rely on the anaerobic metabolism where less oxygen is available. So think the high intensity huffy puffy type exercise, we need oxygen to oxidise fat. If oxygen is not available, we really struggled to burn fat as a fuel source. So we become much more reliant on carbohydrate in our hot environments, which means we need more carbohydrate in hot environments.

Okay, so that's a bit of the nerdy stuff out of the way. I just wanted to explain that because I think it's important you actually get some knowledge in this process. But if you're sitting there thinking, "Yeah, I suck in hot environments" then those are probably the reasons why you might struggle. So what do we actually do about it? Here are my seven strategies to manage exercise in the heat from a nutrition perspective.


1. Heat Acclimation

Number one is heat acclimation. So what I mean by heat acclimation is exposure to a hot environment over a 7-to-14-day period. Research suggests maybe 10 to 14 days is what's optimal. But what it actually does is, it expands our plasma volume, which enhances our fluid balance, and reduces our heart rate too so that we have decreased rate of perceived exertion in the heat. So we want to take the body to a hot environment to expand our plasma volume and feel more comfortable exercising in that hot environment. When you go to a hot environment, you do sweat more. You would have noticed that if you've ever gone on holidays and stepped out of the plane, and it's hotter than you’re used to you just start sweating.

So interestingly, we have an increased sweat rate, but our sweat sodium concentration actually decreases and that's our body's ability to try and conserve sodium. So our sweat sodium loss is the same or lower following heat acclimation. It's not more like you think it might be. Physiologically it makes no sense to start sucking back heaps of sports drink and salt loading when you head to a hot race. So something like Cairns, or Kona, all you're doing is messing up your body's natural ability to adjust.

If you increase your sodium too early, all you're doing is increasing the filtration out through your kidneys, they're really smart. So please don't do that. I'll get a heat acclimation expert on the podcast to help us through how to actually heat acclimatise properly. But it's also important to keep in the back of your mind that if you are heat acclimatised, there is a rate of decay. It's thought to be about 2.5% per day without heat exposure. So you heat acclimatise and you do a heat block. Then you might jump out of that heat for whatever reason, whether it's travel or getting to a race or you were done. Then for each day out of exposure, we're declining our advantages, as a way of putting it, by two and a half percent a day.

So the ideal scenario, maybe if you don't have a job, or kids or any other responsibilities, is you go to a hot race early, and you adapt to those conditions for a good two weeks before your race. Not necessarily practical for all of us. But good bang for your buck if you really struggle in the heat.


2. Drink a sodium-containing sports drink

My second tip is to drink a sodium-containing sports drink. When we drink sodium-containing fluids, it actually helps with better plasma volume retention. So fluid retention. And sports drink was actually originally designed to drive thirst. So it's going to help you drink your ad libitum fluid intake. So not planned sort of drink to thirst. I'm not saying you need to add extra sodium to your sports drink or use really high sodium products, particularly if you don't understand what your sweat sodium concentration is. But just remember, don't simply do what the packet tells you to do. Generally, it's just marketing, designed to help you buy more of their product or stick with their brand. So I'd encourage you to seek professional advice when it comes to training and racing nutrition and find a holistic plan that's practical and evidence-based for you.

This year, I worked with an Ironman athlete heading into Cairns, which is a really hot race, Cairns Ironman, and he wasn't using any sports drink on the bike at all. He's one of my guys that just used gels for the entire bike leg. I calculated how much sodium he had for sort of five, five-and-a-half-hour bike, and he was only getting a total, total sodium intake of 205mg which is very, very low. It's not enough sodium for him, and it's also not driving thirst. So my first strategy for him was to try and introduce a sports drink on the bike. That's going to help drive thirst and set him up for a much better run leg because he was really struggling with the run. So simply by adding sports drink to his bike plan, he went from 205mg of sodium, up to 3660mg of sodium in the bike leg alone. So 17 times more than his original plan. Plus, we did some other top-secret strategies, I'm not going to tell you about those.

But it's a good example of actually having a look at the products you're using. Not just using whatever stuff is sponsored with your team, or what's been given to you or your training buddy tells you to do. Like this guy had done 10 Ironman’s before, and I have no idea how he hasn't walked through my door earlier, but nonetheless, doesn't matter. We're here. And he had the fastest Ironman he's ever done, out of 10 Ironman's with a sports dietitian in his corner, and he had his fastest run split ever as well. So a bit of a shameless plug. Sometimes it's worth the investment in getting some professional help. He was actually going to quit the sport altogether because he just couldn't piece together a solid race performance. And his runs were just killing him. But it doesn't take much a little bit of tweaking a bit of fine-tuning some evidence-based advice. He smashed it, and I couldn't be prouder.

So that's my nudge to look at using a sports drink in your racing and training in the heat. Use it as an opportunity to drink and encourage you to drink more because it drives thirst. There was a really cool study in Ironman athletes where they looked at drinking and dehydration levels and what actually happened. So there was one group where they didn't hydrate them very well, and so they dehydrated to a certain percentage of body weight. There was a couple, depending on how much they were told they could drink, and they restricted them versus drinking ad libitum, so drinking as you need or sort of drinking to thirst, and then the final group was drinking to a set amount of fluid per hour that they determined with sweat testing, to get them to a certain level of dehydration only and not beyond.

What they found were the athletes that drank ad libitum and the ones that were told to drink to a set target to make sure that didn't get too dehydrated. Those two groups performed better than the guys that were not hydrated particularly well. But interestingly, there wasn't much performance difference between the group that drank ad libitum with no plan, we're just told, "Hey, drink to what you feel you need" and the group that had planned set targets of "you need this many mLs an hour to make sure you don't get this percent dehydrated". That's pretty cool.

So if you use a sports drink, and that helps you to drink more, and it drives your thirst. Sometimes that can be a better strategy than not having a plan at all. Unless you've done your own sweat testing and hydration testing with a qualified tester and know exactly what your individual needs are, then maybe drinking more to thirst could help. But if you listen to my episode with Alan McCubbin, I think it's still really important to understand roughly what your sweat rate is so that you have the right amount of fluid available, because we can say, "hey, drink to thirst". But if you're thirsty, and you don't have any bottles left, and it's 20kms to the next aid station, that strategy is not going to be that beneficial for you.


Let me know if this sounds like you. Do you feel exhausted by the end of the training week? Do you crave sweets in the afternoon and feel like you need a nap? Training for three disciplines can be absolutely exhausting if you haven't dialled in your nutrition. It can be frustrating when you can't quite piece together the solid race performance you know you're capable of and confusing when there's so much information out there. But you're not sure what's the right method for you.

My goal for you is to unlock your true potential and feel like a supercharged triathlete, firing on all cylinders full of energy and not only smashing quality training sessions, performing in every race too. If you're finally ready to start nailing your nutrition, join a powerful community of like-minded athletes in the Triathlon Nutrition Academy Program. Head to dietitianapproved.com/academy to check it out now. For less than the cost of a coffee a day, you will finally have a plan for your nutrition instead of winging it and hoping for the best.

So how much sodium do you actually need? Well, with a lot of things with nutrition, it depends. It's highly individual, and you need to understand how you sweat. We know that the highest driver of sweat sodium concentration is sweat rate. So the more you sweat, the more sodium you will lose. But you shouldn't just start popping salt pills or salt capsules because your training buddy told you to do so, or you think it's going to be useful to stop cramping. Go back and listen to Episode 14 with Alan, do you need to take salt tablets for some more quality information in this space. I'd really encourage you to actually develop an individualised protocol based on your sweat testing results in the same environmental conditions. If you need more information on sweat testing, go back and listen to episode 15 where I explained what sweat testing is and who it would be useful for. If you are interested in doing sweat testing, learning more about how it works and when our next sessions are, head to www.dietitianapproved.com/sweattesting.  


3. Keep pace with your sweat losses

Okay, number three. Another really good strategy for exercising in the heat is to try and keep pace with your sweat losses. Now, that's easier said than done. Our sweat loss, our sweat rate, in mLs or litres per hour, is really individual. People sweat anywhere from 400-500 mLs an hour to 3.5L an hour. I've got a few guys that have massive sweat rates of three and a half litres an hour. It's just insane. Like they end up finishing a 20-minute sweat test and their clothes need to be wrung out. You need to do something like sweat and hydration testing to understand how you sweat. Are you a heavy sweater? Are you not a heavy sweater? And if you are a heavy sweater, then you might actually need to build your gut tolerance up to meet your fluid needs if you're not used to having that much volume of fluid, but the first point of call is to actually understand what your sweat loss is because we want to make sure we're preventing dehydration to the point where performance is starting to be affected.

Now 2% body weight is around where performance can be negatively impacted and that's assuming that you're turning up to the start of a session or race hydrated in the first place. There’s thoughts also that the longer events are longer endurance events like Ironman and ultra-marathons and things like that. You can maybe be a little bit more dehydrate better than 2%, before performance starts to get affected, it might be more like 3%, 4% or 5%, potentially. But the difference between 2% and 5% is a lot.

Now, I'm not saying keep pace with your sweat losses, to the point where we're replacing 100%. That's not necessarily useful either. We don't want to over drink. If we're over drinking, we do run the risk of hyponatremia or low sodium. And that is not a good thing. That can be fatal. When we're diluting the body's contents down so much that our sodium levels go low in our blood, that is not good. You're more at risk of hyponatremia if you're a slower athlete because you've got more opportunity to drink, you may not be sweating that much. Versus a faster athlete, you might be sweating more, because the intensity is higher and you have less opportunity to get fluid in whether it's in an Ironman or a race where you're grabbing water cups from aid stations, and you're running fast so a little bit goes in your mouth. But most of it goes all over you. Whereas someone that's walking through an aid station, you can stop and take a full cup, and you have more opportunity to drink.

I really believe that every athlete should do some form of hydration testing, not necessarily sweat testing, but hydration testing. To understand what type of sweater you are. It's something that I teach all my clients how to do, they get a proforma for doing hydration testing on their own at home, on the bike, on the run, in hot weather, in cold weather, and it's something that we dive deeply into in the Triathlon Nutrition Academy as well. So you understand what your fluid needs are so that you can do a better job of keeping pace with that, and not getting too dehydrated where our performance starts to become affected.


4. Keep your fluids cool for internal cooling

Number four is keeping your fluids cool. Keeping our fluids cool, helps to keep our core temperature down and that's what want to do. We want to keep our core temperature below 39 degrees Celsius if we can, because that's where things start to go pear-shaped. Fluids that are less than 22 degrees Celsius will increase their palatability, so you're more likely to consume them and fluids less than 10 degrees Celsius, they have additional benefits with internal cooling. But it's unlikely to be practical in most events, say an Ironman, or even a long-distance trail run without outside help.

One thing you can do is freeze your water bottles overnight for hot training and hot racing. Depending on when you're going to use them or how long they'll be sitting out in transition for, they might melt. But you can kind of test that out and see how long they're going to be out there for and when you’ll use them, they might still be a little bit cool by the time you start using them. And then they'll be warmed up by the end. You can try adding ice to your flasks as well whether that's on the run or going for long runs plus trying to chuck some ice down your clothing. So put some ice on your chest, that's going to keep that central area as cool as possible and provides a bit of an external cooling strategy as well.

The next three strategies that I'm going to go through, are not something to play with unless you've got really specific advice. They are things that I'll do with some of my athletes. But that's because we get to practice and fine tune well ahead of race time and make sure that there's no adverse effects.


5. Acute sodium loading

So number five is acute sodium loading. So I said before, there's no benefit in sodium loading or salt loading for multiple days before you go to a hot environment. You're just going to ruin your body's natural ability to try and adjust. But there is benefit to acute sodium loading, and I'm talking about the one to two hours before a race start, or before you go and do a really long hot training session. So it'd be a pre-event meal. It's highly individual. So I'm not going to tell you how to do it in this forum because it's not something I want you to mess with. If you want an evidence-based plan that's specific for you, then book in for a consultation and I'll help you through it.


6. Acute sodium loading + glycerol

Number six is acute sodium loading plus glycerol. Now glycerol is three-carbon alcohol. It was taken off the WADA banned list in I think in 2018. And what it does is, it assists with fluid retention pre-event by expanding our plasma volume and decreases our urine output. So how much we pee out. Definitely not something to do on your own. I always talk about a nutritional pyramid. And we want to lay a solid foundation first before we start playing with the top tier.


I would suggest that glycerol and even a bit of acute sodium loading is more of the sprinkles on the icing on the cake strategy. You need to nail all of the other things that I talked about earlier first, the first four or five strategies before even looking at doing this one and doing it with a qualified professional that can give you the right advice too.



Now the seventh strategy is menthol. Again, definitely not one to mess with on your own. But what menthol does is, it alters our thermal sensation in our mouth. So it activates our oral pharyngeal cold receptors. You know when you have mint, and you have that, like cooling of the mouth? What it does is it increases the threshold temperature for the activation. So it creates that feeling of coolness. So definitely test it out first, don't party with this one on race day. And if you've got all the other things nailed first and you're working with a qualified professional, then making sure you are using commercial products. Don't mix your own concoction. I have a couple of trail runners who I feel like if I don't put this in here, they will start playing with it themselves. But there's a risk for toxicity, and it can be fatal.

So they are my seven nutrition tips for exercising in the heat. I hope that there's some really practical take-homes for you, including making sure you understand your individual sweat needs, particularly in a hot environment. Whether that involves doing some sweat testing, or just simply some hydration testing to understand what your sweat rate is in mLs per hour, can be really useful when we go to hot environments so that you can understand how to actually drink to that.

Keeping your fluids cool, whether that's freezing bottles or putting ice in your flask while you're running. Anything to keep what you're drinking cool will help with internal cooling. And then you can do some external cooling as well by putting ice on you or ice vests or ice wraps around your neck, etc, etc. There's lots of things available now.

Making sure you keep on top of your hydration heading into your race, that's really important. We don't want to toe the start line already dehydrated in a hot environment, that's not going to end well. Use some sports performance strategies like acute sodium loading to help with managing your hydration before you even start the race as well.

If you are interested in getting an understanding of your sweat needs, then I'd suggest booking in for a sweat test, head to dietitianapproved.com/sweattesting to read a bit more about what's involved. You can register your interest on there as well or you can book in if you're ready to jump in and get sweaty with us. We've got a few dates coming up and then more in the New Year as well. So I hope that helps you manage some exercise over these hot months and start to think about getting prepared for hot races too.

Thanks for joining me for this episode of the Triathlon Nutrition Academy podcast. I would love to hear from you. If you have any questions or want to share with me what you've learned. Email me at [email protected]. You could also spread the word by leaving me a review and taking a screenshot of you listening to the show. Don't forget to tag me on social media at @dietitian.approved so I can give you a shout out too. If you want to learn more about what we do, head to dietitianapproved.com. And if you want to learn more about the Triathlon Nutrition Academy program, head to dietitianapproved.com/academy. Thanks for joining me and I look forward to helping you smash it in the fourth leg - nutrition!

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