Pt 1. Leadville 100 Bike Course Nutrition Prep and Tips from Dr. Lim
July 29, 2023
Select content transcribed, edited, and sourced from Dr. Lim's interview with the Leadville-100 Bike Podcast.
Please remeber numbers for electrolytes, carbs, fluid will vary based on individual needs, weather, effort, etc.
To hear the rest of Allen's tips listen here:
Part 1
Part 2
What should the Leadville racer be doing to feed themselves before the race?
I think that there may be two very distinct approaches. One is a very scientific approach and one is a very hedonistic approach, you can just full on animal, the event, right? And listen to every instinct that you have, that wants to keep you alive, right, which might be knocking down some competitors stealing their food and just hunger gaming, the whole entire thing, right. The other approach is maybe more scientific, but they both are important. And the more scientific approach is to realize that it's not as complicated as it seems. And there are only three things that you're looking to get, you're looking to get carbohydrate, you're looking to get water, and you're looking to get salt, or sodium, right. And if you can nail those three things down, then you're going to be set. The hard part is that it's difficult to predict on any given day, what exactly might you might need, you might be able to guess that you need to be in a certain range. But you still on race day have to rely on that animal rely on that hedonistic urge to drink to eat, etc. Which means that that carbohydrate, that water that salt, better be something that you really desire, right? Better be easy, better be logistically manageable, right. And where I see most people fail, is not knowing that they need to have the right nutrition hydration, they just screw up logistically, right. They don't plan far enough ahead. They don't have an overabundance for the worst case scenario, right? On a day like that. It's better to have too much than too little right. And they don't actually practice that weekend routine enough, right, so that they have a familiarity in case things go a little sideways.
Eating versus Drinking
When I was on the World Tour, that was ultimately what we evolved to, we evolved to a low calorie, simple sugar, you know, electrolyte solution with a amount of sodium that match what the athletes were losing in their sweat, that averages between 800 to 1000 milligrams of sodium per liter. But there's a broad range, some people lose way less, some people lose way more, we'll get to that in a little bit.
And then the notion was that to prevent GI distress, you would load up your stomach with solid food. And the stomach would act as a reservoir for that food. And as that food digested, you would slowly and consistently trickle in nutrients into the gut or the small intestine, or it would be absorbed. The problem in the past with high carbohydrate liquid solutions, like gels or these highly concentrated drink mixes was that because they were already in liquid form, they didn't get held up in the stomach, you had a very high rate of emptying from the stomach. And all of a sudden, as these molecules kind of rushed into the small intestine and broke down very fast. You got a big traffic jam in the small intestine. Effectively the rate of delivery exceeded the rate of absorption by the gut. And anytime you get a situation where you're you present more stuff in the gut than the gut can actually absorb at one given time. What ends up happening is that water then kind of reverses flow and enters the gut, you get this GI distress, some bloating, in worst case scenario, some exercise associated diarrhea. And so we tried to meter the flow effectively put a stoplight in front of the highway and that stoplight in front of the highway was solid food. Alright. That being said, the carbohydrate technology has improved greatly over the last 10 years. A lot due to a company called glyco. That started back in 1905 on a mission to try to develop or produce muscle glycogen as a therapy for people with GI distress. This is a really interesting, crazy, scientific history that led up to the development of these very, very complex carbohydrates. It's around 2010 That didn't really become commercially available until more recently, and these carbohydrate structures digest more like real food, they don't break apart as fast as, say, maltodextrin. They're also very soluble.
And so I think today, it's possible to do both, depending upon what you like, right? Some people still love real food, and they love the tastes. And they love using that as a bit of reward. And it is super satisfying. You just need to be able to find the right amount of time to reach back in your pocket, open something up to slow down, maybe at a speed zone, etc. Others, you know, especially a race, like Leadville will go completely liquid nutrition the whole entire time. I think both can work, if you've got the right product set.
All Images from Skratchlete Greg Erwin.
Heat Stress and Digestion
GI distress can also be caused by just overheating, right? The small intestine is very, very delicate, it's a very thin, small protective barrier that keeps the outside world from coming into the inside world. And when we overheat and we reach kind of a critical body temperature, that barrier can begin to break down. And so even if you have your nutrition strategy, perfect, I see that in you know, heat stress situations, someone with heat exhaustion, etc, that that gut walk and start to fail regardless. And so cooling and staying cool is another primary strategy to being able to be able to get the right fuel and hydration.
What I've seen in performances is that something could be going really, really well. And once they hit this critical temperature is probably like in the 39 39.5 degrees Celsius range, their brain just kind of shuts everything off, right. And there's that aspect of physiology called catastrophe theory, where the idea is that you reach a certain critical point where your brain thinks that you're hurting itself, and it's going to shut you off. And once your brain says no more than no more, right, so you do have to just relax for a little bit. You do have to recover for a bit. You have to make sure your temperature comes down for a little bit. And then you just have to kind of reset and restart, right? And take your time and slowly bring up that intensity and that pace again. So having some idea of pacing strategy, and taking your time and being patient is a big part of that endurance game at Leadville.
What have you observed about altitude and our ability to take a to digest food and convert it to fuel?
You know, altitude is interesting, because our sympathetic nervous system, our fight or flight nervous system gets really ramped up at altitude. And because of that, we primarily use carbohydrate at altitude. And so you do have to feed yourself more carbs when you're up at altitude, because you're just burning through them. It's really, really hard to use fat. And so you might be well fat adapted, right? And you might have a plan where you think that you can rely on those endogenous fat stores for exercise. But if you're not very well adapted to altitude, meaning you haven't spent, you know, that month or month and a half up at altitude adapting that fat adaptation acutely may change. And so you might find yourself at sea level being very well fat adapted, not too concerned about your carbohydrate intake for 100 mile event, you get up to Leadville and all of a sudden, your substrate utilization dramatically changes and you become highly reliant on carbohydrate and if you don't have enough, you end up bonking and you don't know why. So my my altitude problem is a lot simpler than that. Or at least it feels simpler to me when I'm racing the Leadville 100 And that is I am breathing at the absolute fastest I can breathe especially as I get to 12,500 feet and I've been climbing for 3000 you know for 3000 feet straight. And I am just breathing so fast.
It is hard to eat because I am breathing so fast getting something into my mouth, chewing it and then swallowing it while I can't breathe through my nose at that speed or air that level, it is just hard to do so just at that very practical. It is hard for me to ride one handed for that long, when I am at my limit like that. Like a lot of the people who race this race, what do we do? How do you eat at that altitude at that effort?
So what you explained is something that a lot of marathon runners have lamented about they are running. So all out for that two and a half hour or whatever time they're going for that they can't actually consume much, right? They're just breathing way too hard.
Gwen Jorgensen, when she was training for the marathon, she was the gold medalist in 2016. In the triathlon, she had this problem and this is when we actually developed our super high carb formula for her that was built on a carbohydrate called highly branched, cyclic dextrin. This is when things started changing for me from the, you know, kind of hydration, the bottle fuel in the pocket type of strategy. And we began to realize that if the carbohydrate was complex enough and still soluble, that you could actually just drink all of your carbohydrate. And so in that situation where you're ventilating so hard that you can't eat, you don't want to take your hands off the bars, making sure that you have say a Camelback right. And that Camelback actually has a high concentration of carbohydrate.
We have found with highly branched cyclic dextrin, we recommend that you don't go higher than 20% concentration. So that would be 20 grams per every 100 mils. So if you knew you had a 1000 liter bottle or a Camelback, you'd multiply that by point two, which would give you 200, you knew you know that you can put 200 grams of carbohydrate in that.
I have actually found experimenting with athletes that some {high performing} athletes can go as high as a 40% carb low carbohydrate solution with highly branched cyclic dextrin. So you know, you get a lot of freaking carbohydrate, and for most athletes at Leadville, who are say doing, you know, maybe 700 calories an hour or so. And the goal would probably be to replace half of those calories an hour 350, maybe at most 400, you're looking at between 60 to 100 grams of carbohydrate an hour.
And so in one liter Camelback, you know, you might be able to get in at least, you know, 40 grams or so sorry, you might be able to get in at least 200 grams of carbohydrate that can get you through, you know, two to three hours. And depending on your feed zones, you end up switching out those camel backs with that fuel. And then you can put a lighter hydration solution. Some you know something not as concentrated in your bottles, you know, the cluster dextrin is not sweet at all, it's almost tasteless some people have a hard time distinguishing it from plain water. So that ultimately it has been my go to for that situation where you just can't eat, we lean on to the liquid side. But we use the right carbohydrate and we avoid maltodextrin.
To give you a comparison maltodextrin might be anywhere from three to 15 glucose molecules linked together in a chain. So these each glucose molecule or each simple sugar is like a Lego right? And you're basically leaking linking these Legos in a straight chain, there's only one link you need a break to get the glucose molecules you can only transport carbohydrate across a small intestine as a single Lego or as a single glucose molecule or single fructose molecule. In comparison, highly branched cyclic dextrin or cluster dextrin is anywhere from 60 to 100. glucose molecule, glucose molecules linked together in one big molecule. And these Legos basically once in the in their gut they break off one at a time.
What's interesting about gut rot is that it's not the size of the molecule in your gut that causes the change in the water flow across a small intestine. It's the number of molecules, it's the number of Lego pieces. But if you can put all those Lego pieces together in one big molecule, they act as one piece, right? And so what we can put in a lot of calories, and as long as we can kind of slow that break down a bit. Then we're safe. And that's why these new very complex carbohydrate structures are great. And this is where, you know, I just tell athletes, hey, just don't use maltodextrin. And you're probably going to be okay.
We heard last year of athletes shooting for especially in the lifetime Grand Prix, shooting for like 120 grams of carbohydrates per hour that works out I think about 480 calories per hour. What are the upper limits for carb intake per hour, especially as it pertains to maybe the the the amateur athlete?
The Pros consuming 120 grams, that's matching an energy expenditure where somebody is doing about 1000 to 1100 calories an hour, and you have to be able to win up Leadville or in the top 10 of Leadville in order to need that much energy, right. And so I do think that what's interesting is that things are in proportion, the same physiology that might allow you to just go that fast when a bicycle also probably is met by the ability to absorb that much carbohydrate, alright. So they kind of go hand in hand. And in some situations, you might find an athlete with a big engine, but low intake ability, right, and that's when they might get screwed might be better suited for shorter, faster events. For most individuals doing Leadville, you know, you're gonna be anywhere from 400 to maybe 700 calories an hour. And the rule of thumb is replace half the calories an hour, right? And so if you're replacing half the calories you burn per hour, you are at, effectively your upper limit for absorption, right, and there's no need to try to over do that. So you might find someone who is doing, you know, 500 calories an hour only needing to consume about 50 grams of carbohydrate an hour, right? And that's a lot of carbohydrate.
Does it make a difference if I'm a larger individual or smaller individual?
It does your energy expenditure is going to be proportional to size. And so bigger people are going to be burning more calories just because of that bigger mass bigger size. The best way to get an estimate of your energy expenditure for a day like Leadville is to have a power meter right and to know that a power meter measures mechanical work and by this little quirk of nature 1000 kilojoules of mechanical work is about 1000 calories of energy burned right you It actually is more like 1100 calories of energy burn for most human beings. That's because our bodies are only about 25% Gross, mechanically efficient. So if we consume 1000 calories, only about 250 actually goes into producing power on the bicycle. But by another court of nature, the conversion of kilojoules to K cals is only four to one, so they cancel each other out. So if you have a power meter, and you know what your paces, then you'll have a good idea of how much energy you're burning, if you end up knowing that you're going to do 4000 kilojoules of work. At Leadville, your goal is to get at least 2000 calories in for that day spread across, however many hours you're going to be doing.
Is there a way to train my body up so that I can bring in more calories, and therefore hopefully have more fuel available to my engine?
I think you can, but what you're really doing is you're still reliant on a big cardiac output, you're still relying on blood flow, you've got to get consistent blood flow into your small intestine in order to increase absorption of nutrients. And the thing is, is that there's this major competition for blood flow during exercise, right, you've got to use blood flow to not only deliver oxygen to working muscle, but you've got to use that blood to remove co2 to remove excess heat by bringing blood to vessels in your back and to your skin so that you can actually cool off by sweating, you're losing blood because of sweat.
And now you've got to also bring blood to your gut in order to absorb things. what that all means is that the compromise ends up being pace, right? You've got to find the pace that you can keep up for that whole duration that optimizes for all of those four different things, right, removal of co2, delivery of oxygen, removal of heat, and, you know, bringing nutrients in the small intestine. So I think the biggest mistake people also make an event like, like Leadville is if you go out way too hard. Or if you pick a pace that is simply too hard. It's not going to matter, because you're going to be in taking all this carbohydrate. And you're you may not be able to absorb it if you're going too hard.
And so even the best athletes there who are out to win the event, know that they still need to be riding in that kind of sub threshold, pace, that pace where they probably can't sing, but they can probably still talk.
Skratch has a high-carb drink mix but no gel, what is the deal with that?
The distinction between our super fuel and the gels is just that the gels already come prepackaged. So what we tend to do is, we give athletes these little 150 mil flask, and we will put in a bout a 30% concentration of the super high carb. So you know, 150 times point three, it's like, yeah, we get in, like about 40-50 grams of carbohydrate, and each one of we know that an athlete's on pace to, you know, do nine to 10 hours at 50 grams per hour, they're effectively, if they were going to fuel with these little soft glass, we know that they probably need about 10 of these. And so they might start with four of these in the pocket. And then they'll pick up three to four more at each feed zone and be a-okay, so it ends up being pretty simple if you can get the right amount of carbohydrate. And we like these flasks, because they're just a little bigger, you can get a little more carbohydrate, they're a little less wasteful, less wasteful than tearing up a bunch of gels, and the super high carb ends up not being sweet. So it ends up being a little more sustainable. And it keeps things very simple. I think that, you know, most gels are about 20 grams of carbohydrate. And so it's very conceivable that if someone was just using gels as a fuel source, that over 10 hours that they're going to be going through about 20 to 25 of them. And so being able to just go through, say 10 of these flasks that fit in the pocket pretty well ends up simplifying things. But that's just one strategy, right? You can also turn your Camelback into kind of a big, high concentrated carbohydrate solution as well with the super high carb formula.
As far as gels go... what we're trying to avoid... sugar fatigue, right? I mean that it's a big bugaboo is what it does to the palate and our ability to keep taking that in.
I think that most gels are not that complex, most of them are made with either maltodextrin or just plain sugar. The issue ends up becoming, if you take too many at one time, again, since this stuff is already liquified, it doesn't sit in the stomach too long. And it can rush into the small intestine fairly fast. If you are kind of metering that gel on your own, and you are the one acting is that stopped by and policing things and trickling it in, I think that you can be okay. But I think that you get an a problem if you try to take too much at one time. And so another important strategy for Leadville is you do if you are using really sweet gels, you have to meter out your dosage. You can't get into a panic and think that by taking in a bunch at one time that you're gonna save yourself, right at that point, you might be doing more harm than good.
You want to think about it in terms of your carbohydrate need per hour. And let's just say that that's, you know, 60 grams an hour, well, that might be two gels and one water bottle, right what sports drink in it. And as long as you're consistently getting in those two every hour with that one water bottle, even if you feel good, that's way better than getting four or five hours in realizing that you're bonking and then tried to take in a bunch of, you know, carbohydrate at one time can make up that difference, you won't be able to make up that difference, you'll probably just be causing a situation that you might get GI distress.
What is the difference between men and women and how and how we ought to prep for and consumed during the Leadville 100?
The nature of that is it really comes down to fitness level is probably more of a determinant of what you actually need to consume than any other variable. What are the pace and the fitness and the power differences between the two of us, that would explain most of the nutritional differences you need on that particular day? There are always individual differences, even within gender, that are more profound than the differences that you might be able to assume between, say, men and women when it comes to that acute fuelling day. Now obviously, if you were to think about nutrition, very holistically, big picture, you know, in terms of stage in life, and you know, a woman's menstrual cycle versus a man, you might find some important differences in nutrition that needs to be accounted for. But on that given race day on that single day, most of it is going to come down to pace and fitness.
More Leadville 100 Bike Fueling Infomation can be found here.
To hear the rest of Allen's tips click here.
Part 1
Part 2
For more sports nutrition advice and recipe check out Dr. Lim and Chef Biju Thomas' cookbooks
