Fuel & Hydrate to Avoid Bonking: Prevention Strategies for Endurance Athletes Ep 91
17 Apr 2025 · 10 min
Coach Christina Fiumara Newport explains bonking, the sudden fatigue from depleted glycogen stores that typically hits around the 3-hour mark in endurance events. She recommends starting with 30-60g of carbs per hour, training your gut with multiple carb sources, and testing your sweat rate to dial in fueling and hydration for your body and conditions.
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Every endurance athlete remembers the moment when things finally click. Your swim feels smoother, your pacing makes sense, your fueling works, and suddenly the sport feels not only easier, but more fun. And for many athletes, that moment happens at training camp. That's exactly why we created the Endurance Edge Triathlon Training Camp happening April 22nd through 26th at Lake Jocassee in South Carolina. For 4 incredible days, you'll train in a small group with expert coaches, sports nutrition support, and sports psychology guidance, all designed to help you train smarter, race stronger, and finally connect the dots in your performance. We swim in crystal clear mountain water, ride beautiful and challenging roads, run scenic trails, and spend the rest of the time recovering, learning, laughing, and eating some seriously amazing chef-prepared food. Mm-hmm. Camp is intentionally small, just 20 athletes, so you get real coaching, true connection, and amazing breakthroughs. So if you want an experience that can transform your entire season, we invite you to join us. Head to theenduranceedge.com and click training camp and reserve your spot with just a $100 deposit. Come train hard, learn a ton, and leave stronger than you ever imagined. I'll see you there. Hey y'all, and welcome back to the Find Your Edge podcast. I am so glad you are here. This is Coach Chris, and today we are talking all about the nightmare that is bonking and how to help prevent it. So if you've ever had the feeling of literally running into the wall when you've done exercise, I mean, and that's why they call it hitting the wall. You literally feel like you have ran into a wall and you cannot move much more. That is bonking. In other words, it is running out of energy that you need for exercise. So we're going to talk about some strategies to prevent the dreaded bonk. So I can tell you, I've definitely felt like this before. In fact, I was in the middle of a half Ironman, and at the end was so hot and so miserable and so done, I decided that it would be a good idea to literally dump out all all of my water bottles. So that was a regrettable issue. And I also went out too hard. So pacing is definitely part of this equation as well, and training for sure. So let's get into what bonking actually is. It is what's called glycogen depletion, which leads to literal rapid fatigue. One of the best ways to restore your glycogen is to ensure that you're consuming enough carbohydrates, or you rest, or a little bit of both. You rest and you take in those carbs. So typically this will happen usually around the third hour of intense or more long duration exercise. So putting that into, say, a marathon, usually if you hang out sometime around the 21-mile mark, usually you're gonna see this in action if somebody's not been fueling properly or if they've been pacing improperly as well. This might be just over like a half Ironman type of event. You might get in there a little bit with Olympic distance. Probably not quite as much, but it's really more half Ironman, certainly Ironman, and definitely ultra endurance types of activities. So the longer the duration or the harder, uh, more intense that you're going, the more likely you're going to run out of that glycogen. So what it might feel like, other than literally hitting the wall or bonking, you might have some shakiness, you might have a little bit of dizziness, or you just might wanna You just might wanna be done. You might be a little confused. If you Google on YouTube Ironman crawling across the finish line, there have been some notable famous professional triathletes who have literally crawled and shook as they have come across the finish line because they are just so toast. So that may be what it looks like, but how much glycogen do you actually store. So funny story, when I was doing my thesis at Meredith College, I wanted to take glycogen from my subject, and unfortunately the IRB did not let me do that because they didn't want to break the skin. It is pretty intense if you, if you measure glycogen levels, it does involve a muscle biopsy, so it's no joke. But if you want an estimation without getting a giant needle stabbed in your thigh, which I'm assuming you all do, it depends really on your size. So the bigger the human you are, the more glycogen you're going to be able to store. Of course, the more energy you burn, and vice versa. So the smaller you are, the less you store, but you're also burning fewer calories when you're exercising, right? So it's all kind of six to one, half dozen the other. But depending on your size, you store about somewhere around 400 to 600 grams of glycogen in your muscles specifically. And since 1 gram of carb is approximately 4 calories, that translates to somewhere around 1,600 to 3,600 calories of stored energy, which again is strictly in the muscle. Now you also store it a little bit in your liver, but that's not a too terribly large amount. It's somewhere around 60 to 90 grams. Through training, your ability to use and store glycogen actually improves, right? So that's one of the purposes of training. So hopefully you're doing that before you're doing some sort of hard, intense event like marathon, or like a half Ironman, Ironman, or longer distance. So it is delivered through the small intestines. So when you're actually needing that energy, that's where it's going to be pulled from. And interestingly, you and I— well, me sitting in this chair right now, and you maybe on the treadmill or driving in your car, wherever you are— even if you're not exercising, you're still using it right now. So it's not something that's exclusive just to exercise. You're using it on a regular basis even if you're just resting. So this is where your dietary patterns come into play. So carbohydrates are your friend in this case. They are your fuel, certainly for endurance activity. So again, glycogen is the stored form of carbohydrates, and once you run out You crash. So no fun. Nobody wants to have a terrible performing day. Nobody wants to get overly tired or have that higher risk of hypoglycemia, especially if you're somebody who tends to be at risk of low blood sugar. No good. So some of that low blood sugar symptoms could include things like headaches, shakiness. You may even pass out. So carbohydrates, quick reminder, where do they come from? Certainly grain starches, things like bread, pasta, rice, baked potatoes, sweet potatoes. They also come from from vegetables, they also come from fruits and all those good types of things. And of course, the engineered foods that you might think of more from a sports nutrition perspective. So sports drinks, gels, chews, and then you also have some natural fueling sources like bananas, raisins, dates, things like Clif Bars, LARA bars, oats. So the list goes on and on. Generally speaking, it's not particularly hard to find carbohydrates in our, in our food, or to be able to purchase them, whether you go to a running store or you get something online, or you go to the grocery store, or you go to the gas station. So they're pretty ubiquitous and easy to find. Then it's just a matter of how much do you need when it comes to exercise in order to avoid this bonk. So first of all, I do want to make sure that again you're training your gut as you are training your body. Certainly as you get up into those longer distances, those longer runs, those longer rides, this is something that you need to practice. Generally speaking, and we, we test this in the lab and we actually see how much energy are you using from carbohydrates and from fat as an energy source at different intensities during a certain type of movement. So in our lab we do rowing, running, and cycling, so we can actually see what is your carb burn or glycogen use and what is your fat oxidation. So hopefully as aerobic athletes we are using some fat as an energy source, but the faster you go, the less fat you use and the more carbs you use. Therefore, the higher likelihood that you're going to run out of these. So a good starting point— and I don't want to overgeneralize, and this is where we get much more nitty-gritty in our Fueling and Hydration Boot Camp that starts in May, so you can find out more about that and get on the priority list at theenduranceedge.com/fuelingbootcamp— but a good place to start is somewhere around 30 to 60 grams of carbs per hour for exercise purposes. All right, so usually I have my women start on a little bit of the lower end, and I'll oftentimes have my men start a little bit on the higher end. You can— let me back up here for a little bit. Your gut, from the literature, we have seen that it can oxidize 1 gram of carb per minute, and then we go What happens after that? So what is going on in literature right now is how can— so in other words, the gut is the major limiter for our ability to push harder because we can expend a ton of energy, but how do we keep going and how do we keep going harder for longer? And being able to fuel our bodies appropriately is one of the major limiters in exercise.
Our gut.
So if we see that you can generally oxidize 1 gram of carb per minute, how are we able to push that number up? And so what's going on in the literature right now is trying out all these different combinations of different types of carbohydrates. So you are most effective in especially long distance. So I'm going to say like, uh, 3 hours plus 2.5 to 3 hours plus, getting 2 types of carbohydrates in whatever you're using for exercise. So that's some types of carbohydrates that you might recognize if you look at the label, or if you're purchasing a particular product, is good old-fashioned sugar or sucrose. You might notice glucose on the label. You might notice dextrose. Or maltodextrin. You might notice tapioca syrup. So there are dozens of these different types of carbohydrates that are used in various products. We want to make sure that the product has at least 2 of those types of carbohydrates. Now here's the fun part. Where we're able to see that athletes can increase their ability to oxidize carbohydrates is when we tack on fructose. So fructose is isolated from fruit and is what makes fruit sweet. So if we add in fructose, which has to make its way— again, you consume these things, they're what's called exogenous carbohydrates for exercise, things like gels, chews, sports drinks. Again, it can be natural sources like bananas, dates, raisins, etc. When you consume them they have to get through your stomach and down into your small intestines, and then fructose has to go to the liver and then make its way to working muscles. So it's a little bit of a longer pathway, which is why there's some thought of, oh, we can increase our ability to take in fuel or take in nutrition, specifically carbohydrates, to be able to be delivered to working muscles when we find that nice balance of glucose and fructose. So you are unique and wonderfully human. I hope all of you know that, and I'm going to continue to say that many times, but you are a fabulous human being. But what we see, at least in the literature, is good starting point. We might see that like a 2:1 is working, but there's a million different ways to skin a cat. And this is why I love the Fueling Boot Camp, because we can get really nitty-gritty into all different types of strategies, in particular based on your specific sweat testing needs and what your particular race— and then we come out with— you come out with this wonderful strategy that's all written out that you need to go test, and we help you guys test, and it's, it's really fun. Anyhow, so that's the way that we can up that number from 60 to 70 to 80 to 90, maybe even to 100 to 120 grams of carbs per hour. What it really comes down to is what you are able to tolerate. So my recommendation is that you start small and make sure that you are getting something that's tolerable. So in other words, your gut is able to handle it. Some people have far more sensitive guts than others. That's a whole nother podcast, and there's a bunch on GI distress specifically in our Fueling and Hydration Boot Camp. So what can you tolerate? And then what do you like? So in other words, what's palatable to you? So what's tasty? So for example, and not to throw any particular product under the bus, if you gave me Gatorade, I probably will stop drinking. It's too sweet, makes my mouth feel funny, and then I just will stop drinking it. So something that's much less sweet. I'm also not the biggest fan of stevia-related products. It just tastes funny to me. So that eliminates a ton of different products for me personally. That's just one example of the different types of products and how many options right now in our fueling calculator that you get as part of this bootcamp. There's, uh, well over 140 different products in there, including natural products, engineered products, and we're not done yet. There are still things that people are like, oh, this isn't in your calculator. Then we add it in. No problem. So your fueling strategy and your unique formula is perfect for you. So that's a way that we can start to push those increased numbers. That doesn't mean that you start off at 120 grams of carbs or 100 grams of carbs per hour. It's all in adding in that little bit of extra and then finding what's tolerable and what's palatable and which logistically you're able to execute as well. So I'm one, I very much dislike feeling nauseous. So I would try this in very small increments, increasing the carb. And then right at that point where I'm feeling nauseous, oh man, you best believe that I'm, I'm cutting that off. So as a little example, I often see triathletes who will over-push their, uh, potentially their pace, but certainly how much they're trying to ingest on the bike because they're like, oh, I've got like a roving kitchen here, may as well take as much as I possibly can in. And then they get to the run and it's like the brakes go on because all of that that has gone from their stomach into their small intestines is just hung up there and it's just not able to move. So then you get a little bit nauseous, then you've got to slow down, then you can barely get anything in, and then we've sort of dug ourselves into whole. So consistency is certainly important. So anyway, 30 to 60 grams of carbs per hour is a great starting point, and then move your way up from there. Your magic number might be somewhere around 80, might be somewhere around 90, might be somewhere around 100 or more. Keep in mind that heat will decrease typically by about 10% your carbohydrate— your ability to oxidize carbohydrates, your ability to actually use it. So if you're taking it in, it's gonna— it's more likely to just kind of sit and be slow because your body is is sending so much blood to your skin in order to sweat, to dissipate heat, because your core temperature is rising. Your body so desperately wants to protect you and obviously keep you alive. And if your core temperature rises too much, that's when we get into heat stroke territory. So no bueno. Anyhow, factors that affect carb needs Again, we talked about body size, certainly exercise intensity, and we can see this when you come into the lab. If you ever work in our— if you ever come into our metabolic testing facility, we can see, okay, at this easy pace you're using 60% from fat and 40% from carbohydrates, or whatever that might be. Where's your crossover point where you're at about 50/50? So how efficient are you using fat as an energy source? When do you go to that anaerobic threshold where you are turning into 100% from carbohydrates as an energy source? Of course, we're going to go through that glycogen really quickly at that point. Typically, that aligns your FTP. If you're familiar with lactate threshold, usually lactate threshold slash FTP slash anaerobic threshold all generally occur around the same time. They are legitimately different things, So they may not, they may be slightly at different points, but they're all kind of roughly in the same category, which if you are working at your threshold, you're probably not gonna be able to hold that for a terribly long period of time. That's really hard, right? Anything threshold or above all the way up to max is certainly hard. If we're gonna be going for 3+ hours, which is when we get into potential glycogen depletion territory. We're likely not going at threshold. Anyhow, one of the things that we need to do is how do we actually get those carbs during exercise? So options that you can have, we already mentioned some of these sports drinks, gels, chews, bars, real food, bananas, raisins, dates, et cetera. So again, just a little reminder, make sure to train your gut just like you train your legs. So if you're going out for a 90-minute or a 2-hour ride or run or whatever, you better believe that you should be practicing your hydration strategy because your gut is an organ too, and it gets trained just like your legs, your arms, et cetera. So practice eating and drinking during training. If you're somebody who's maybe not as confident on the bike perhaps, and not as good at grabbing your water bottle or using bike balance techniques, certainly get a coach to help you with using certain strategies to make sure that we can get you to stay upright and that you can practice eating and drinking while you're cycling, eating and drinking while you're running, et cetera. So make sure that you're not trying anything new on race day. So train your gut like you train your legs and be sure that you are not trying anything new on race day. Keep in mind, because everybody comes to me when they're visiting the porta-john a lot, keep in mind that your mental training tools can affect your gut as well. So that is your nervous system. Going on overload, it doesn't necessarily mean that you ate something wrong. It might, certainly could, but keep in mind that those go together. So our nervous system and our gut, they like to work together. All right, so ensure with whatever fluid you're doing— remember, your fluid and electrolytes should be the same. They should stay the same no matter whether you're in cold environments or hot environments. and we see that with sweat testing and we're able to actually tell you what should your concentration of your specific formula look like. Now, if that means that you want to add in carbohydrates via a sports drink or some particular sports drink matches for you, great. So, and you like it, you're more driven to drink and you can do that consistently, fantastic. Then definitely do that. Okay? And again, make sure that you have those two types of carbs. Certain products that tend to work well for a lot of our customers. I'm not attached to any of these. We are product agnostic. I don't care what you use, guys, as long as you're getting something down and you're able to move that body in an amazing way. And I totally believe in you, and I am here for you and all the amazing hard things that you want to do. We have people who enjoy products like Tailwind, Scratch, Infinite, Goo, Salt stick element. I mean, there are tons. Like I said, there's, uh, over 140 different products in our fueling and hydration calculator that is part of our Fueling Bootcamp. And just a quick reminder that taste does matter. Uh, we were just revising our hydration guide, so you can find that on our website, free download. It's great. It's beautiful. So our designer did such a fantastic job and I had our current intern help us out with making that. So love it. It really, really looks good. I would love your feedback on it. Anyway, as we were creating that, one of the things that came up in the literature is that taste really does matter. So you really have to enjoy whatever it is that you're fueling and hydrating with, or else it defeats the purpose. Little tips for certainly Ironman or ultra endurance, rotate your flavors. Some people get some flavor fatigue and then they just don't want anything anymore afterwards. I have created my own sports drink and we, we also have one on our website. Happy to share that as well, but you can create one for yourself too. But it's kind of one of those things like I will annoy the heck outta my training partners cuz I'll take a sip of my sports drink that I have made and be like, mm, mm, that isn't that lovely. And, uh, I have found that I'm a little bit obnoxious after doing that, but that's how it should be. You should enjoy whatever it is that you're fueling and hydrating with because hopefully you're enjoying whatever it is that you're doing for exercise and that you are crushing goals and taking names. I love it. So with all of that in mind, so that you avoid bonking, ensure that you make a plan because at the end of the day, personalization is key. Consider if you have any medical conditions, consider if you're on any medications, that's important too. Consider your sweat. testing needs. So your sweat is kind of like your fingerprint. So I was just talking to a gentleman earlier today who is losing over almost 80 milligrams per ounce of sweat. And then I've also worked with people who lose anywhere from 15 to 20 milligrams of sweat per ounce. That makes a massive difference in what your plan is gonna look like. Then knowing what is the temperature and humidity so that you can get dew point. We have all of this in our sweat calculator, and we also send you a hygrometer so that you can hang it outside and see, okay, I'm headed out for my run. What's the temperature? What's the humidity? The dew point gets calculated, and that is important information to create our scatter plot chart that indicates what is your intensity, what is the dew point, and how much are you sweating. And then you've got this information going into whatever race it is, whether it's in January or September or July in Australia or North Carolina or Florida or Minnesota. Doesn't matter. And then you have that information so that you can create that personalized fueling plan so that you can go farther and faster without bonking. So bonking is preventable with the right carbs, the right strategy, and practice, practice, practice, practice. So certainly we want you to fuel smart. We certainly want you to Race strong and use that personalized plan so that you can avoid bonking. So if you wanna take the guesswork out of your fueling and hydration strategy, then come check out the Fueling and Hydration Bootcamp. Would love to have you there. It's a comprehensive program designed specifically for endurance athletes who wanna go the distance without cramps, without GI distress, or energy meltdowns. You get access to expert live coaching calls with me personally. You get practical tools like our hydration calculator. We have Just come out with a brand new edition based on your feedback so that it's even easier to use. We've got fueling templates and we've got an amazing community of like-minded athletes who are learning how to fuel smarter of all ages. Y'all, we've got people in their 20s up into their 70s who wanna do amazing things for yourselves. So we only open the doors once a year and right now get on the priority list. Because the doors will only be open for a couple of days in May. So if you get on the priority list, you're gonna be the first one. To know. So check it out at theenduranceedge.com/fuelingbootcamp to join us and make your next long race your best one yet. So train smart, fuel smarter, and whatever you do, don't bonk. Thanks again for listening.
Thanks for listening to the Find Your Edge podcast. If you like what you heard, don't forget to subscribe on your favorite podcast platform so you never miss an episode. And if you're interested in learning more about our endurance coaching, sports and wellness nutrition, metabolic and sweat testing, triathlon training team, or our triathlon training library, be sure to check us out at theenduranceedge.com. And don't forget to follow us on social media at The Endurance Edge. Thanks again, and we'll catch you next time.
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