In this episode, the Athletes Compass team discusses the science of fuel adaptation, focusing on how athletes can optimize performance using fat or carbohydrate energy systems. With real-world insights from endurance athletes, they tackle the benefits of metabolic flexibility, the transition from carb to fat adaptation, and why both may be crucial for peak performance in different race lengths. They also cover HIIT adaptations for various athletic profiles, overtraining indicators in Athletica, and how to effectively incorporate heat training into workouts. Finally, they dive into cutting-edge sports technology like glucose and temperature monitors to evaluate their evolving role in training.

Key Takeaways

• Fuel Adaptation: Athletes can perform high-intensity workouts effectively by training their bodies to rely on fat, which helps conserve glycogen for bursts of energy.
• Metabolic Flexibility: Developing the ability to switch between fat and carb metabolism enhances endurance and optimizes energy use for varied workout intensities.
• HIIT for Profiles: Tailor high-intensity interval training (HIIT) based on whether an athlete is more endurance-focused or fast-twitch-oriented.
• Heat Training: Incorporating heat into workouts improves cardiovascular efficiency and performance in warm climates.
• Athletica’s Overtraining Warnings: These alerts are guidelines to prevent burnout, reminding athletes to monitor recovery needs alongside performance metrics.
• Emerging Sports Tech: Devices like continuous glucose and core temperature monitors show promise but require further development to be fully reliable for athletes.

• Athlete Profiling Primer
• Paul Warloski - Endurance, Strength Training, Yoga
• Marjaana Rakai - Tired Mom Runs - Where fitness meets motherhood.

In the fat adapted state,

got this foundation, this enhanced foundation of metabolism that's providing energy to the body,

right? So the more your

system is burning energy, burning oxygen to provide ATP (Adenosine triphosphate) as energy, the less it's relying on carbohydrate as a fuel substrate,

Hello and welcome to the Athletes Compass podcast where we navigate training, fitness and health for everyday athletes. Today we have listener questions and my friend Dan Neff has been listening to our podcast on the way home from cyclocross races and he keeps asking us about this fat adaption and working with our nutrition. So here's his new question. He's been refining his thinking. So with our short

of races like cyclocross, crits or mountain bike races, road races, is there a benefit to being fat adapted versus being carb adapted or being carb adapted for the endurance things like Ironman or 24-hour racing or 100-mile gravel events? And then we go on to ask, what does it mean to be metabolically flexible and how does it apply to consuming fats and carbs as a fuel source? That's a lot in the question. So let's start with that first part.

about short events versus long events.

Mm-hmm.

Yep, it's a super question. You know, this is debatable out there and it probably depends on what camp you kind of hang out in. But you know, there's this classic sciencey paper written by colleagues of mine, Tim Noakes, Jeff Molleck, and it basically brings out the global holistic benefit of being fat adapted.

In the fat adapted state, whole, you you're basically anchoring, you've got this foundation, this enhanced foundation of metabolism that's providing energy to the body, right? So the more your fat system is burning energy, burning oxygen to provide ATP (Adenosine triphosphate) as energy, the less it's relying on carbohydrate as a fuel substrate, as

as one example. So even in the crit or spiky situation, it's nice if a good proportion of your energy needs are already being met by that. so I had Swain Tuft, who's I know Paul knows, but he's a famous cyclist, friend of mine, famous cyclist, multi-tour de France wins.

Giro pink jersey wearer, et cetera, et cetera. Right. So it's like, you know, he, told me when I was interviewing, it's like road cycling in any form is about how can you reserve your yourself for the high intensity boats and fat adaptation is one way that you can protect those resources. so, you know, he learned that and, know, he, he, you know,

know, Swain adapted his diet. He was one of the earlier adopters kind of doing that when everyone else was doing it. And, you know, it was many of his, it wasn't, you know, it wasn't that a lot, he didn't get a lot of wins before that. He was already an immense talent and training goes a long way to providing that foundation that we're talking about. The nutrition was one extra lever that, that Swain learned to pull, especially as he became more of an aging, aging athlete. You know, that's so,

I think that's, you know, and there's a whole bunch of other, you know, advantages as well. There's enhanced recovery. There's more of the ketones that are around in your body, right? And the ketones, remember, we've learned on former podcasts that this is the macronutrient that is made by your liver when carbohydrates are kind of lower, when your insulin is low and your...

you know, your glucose is low, it forces the liver to turn those fats and amino acids into, via the process of gluconeogenesis, into glucose and ketones to supply that for the rest of the body. So the more you can rely on your fat stores, which are unlimited in all of us for argument's sake, the more it just provides an overall foundation of recovery and energy needs.

sustained energy during the day and in your activity to save yourself for those important all out spikes that you want.

what about then like all out efforts, people often say if you're in key doses or low carb, those high spikes of power are planted.

you know, there's a total other camp. If we're talking like, you know, you're an anaerobe totally. You know, I think that the jury is probably still out on that. there's, especially in the young athlete context, you know, they can burn a lot of sugar. I was one of them a long time ago and I could do the same thing. yeah, for those, for that context, it's probably just fine.

We're still learning in this area. And again, we have to all acknowledge that we don't know everything. Tim Noakes and others are working on a construct where really the only thing that matters in these sprints are a balanced level of blood glucose. And the whole metabolism aspect is somewhat, we don't really know how much energy, sugar burning energy, anaerobic energy.

is absolutely necessary. And if we look to another scientist that contributes to science, Peter Wann, he's the godfather ultimately of the anaerobic speed and power reserve. We've gone through on another podcast before and he says, look, there's no evidence really that anaerobic metabolism is necessarily fueling some of these very short all out efforts.

It's just, it's an amazing transfer of energy. We're not saying that those aren't actually occurring and those processes don't happen in the body. We're just saying that you don't necessarily have to have like, you know, sugar as the energy metabolism present and especially external sugar, exogenous at levels, right? You don't have to consume sugar necessarily for that to happen.

Remember that we've got a whole bunch of sugar that's stored in the form of glycogen and liver glycogen is just sitting in there, muscle and liver glycogen, ready to go. And that's all been put in us as we all slept last night, right? All of the food that you ate last night for dinner in any form, it could have been totally protein and fat-based. It all still would have converted over to carbohydrate through the process of gluconeogenesis. That's how we're built.

So that's all sitting within you. You don't necessarily have to go and douse a whole bunch of sugar on the flame to make it go. The evidence is slim on that one.

So this might come as a shocker then that you don't have to eat your gels before your 5k race

you

No, you don't have to. mean, don't forget there's, think about what, you know, we know all the studies from Asker Jeukendrup and others, about the mouth rinsing studies, there's no question there's a response there, but it might not be from a sugar burning standpoint. It's more of a central nervous system stimulant, right? Sugar itself, we know it's like a central nervous system stimulant. So those, and the mouth rinse studies showed that. just to to elaborate,

know, subjects just took in a mouth rinse of sugar and they spat it out. So that no possible metabolism of that sugar could take place. But just the act of actually brushing the palate with sugar was enough to stimulate the brain to say, we must have sugar coming into the system and that we're gonna be great. And the performance was enhanced just with that process.

Hmm.

Proving that it is a central nervous system regulator in terms of that response that you're getting so sure if if you know use a gel if it makes you if it gives you that you know pop and and that helps that's that's valid and we'll take that but just know it's probably not from a metabolic sort of standpoint it's more from us it's stimulating your CNS, but if you want to think sort of more gloot Google Earth or broadly get your whole system just

healthy, right? This why we're always promoting being a healthy athlete. Make sure that diet is just like, you know, is solid and bulletproof. And then that whole, that should support, if it's whole food in general, that should support a strong foundation of aerobic metabolism that we can build off of so that, you know, our, you know, those, back to Paul's initial question.

of Dan, so his big spikes and surges can be as strong as possible. But he's going to mostly get that from his training, being familiar with doing those spikes, probably a little bit of gym work as well, right? So he can maximally recruit during those efforts. And then having the solid, healthy foundation to recover from all those efforts. Those are going to be the big rocks. It's not

not throwing any sort of gasoline on the engine. That might be a top up. It's probably coming from a central nervous system stim.

you

I don't want to move on yet because I hear and I see read questions about low carb nutrition for athletes, especially like Olympic distance or like half marathon compared to marathon or Ironman distance. And I assume the answer is the same because if we're talking about like two hour race,

three hour race, don't need to fuel up that much compared to long distance, right? Like we have everything we need on board already, but a lot of athletes are fueling with gels and sports drinks during those shorter events that last about two, three hours.

Yeah, for sure. those are, know, in those ones there, there's, there is a contribution of that, of, you know, I should backtrack a little bit now. So we're moving away from the spikiness now, and now we're moving in more to the two to three hour range. Now we're, now we're kind of, that's what we're talking. So now we do know from tracer studies, right? This is one, like they do carbon dating with the tracers and they actually can see how much of the carbohydrate, carbon, carbon molecules of the carbohydrate are actually being metabolized.

when we actually do that exercise, right? And they're showing, I believe that about 75 % of that can be oxidized, okay? So yes, we can get a contribution to those additional carbohydrates. Some of it, not all of it, but some, you know, a good chunk of it actually gets metabolized. Some of it just stays in the bloodstream. And...

Yeah, that could make a small contribution to the performance in those events. And look, there are athletes, successful athletes that swear by the Morton gels and all these various different things, right? And I think the jury's kind of still out on those, but if that's working for you, I think that's great. We know it works well in the younger context. So if you're a twin,

an early teen or late teen or, you know, an early twenties to maybe even early thirties athlete that might work really, really well for you. Something happens as we grow older where our ability to process that sugar. So what it is goes down. It just doesn't seem to work kind of as efficiently. So that's when you might want to sort of consider more of the fat adaptation.

context and of course, I would say even earlier too, it's probably a good practice. I think there's not a lot of evidence to me that fat can't do a lot of the same work that any of that sugar or carbohydrate is doing in those other studies. think we know we can get fat metabolism rates up to

you know, two grams a minute, right? So this is guys like Dan Plews setting the world record for the Ironman and the age group, you know, going under eight hours or winning the Kona one. We know his fat adaptation rates are, you know, he's managed to build those to ridiculous levels. And I know he certainly does not need these gels to go as fast as he does. So as one example.

and I

But for everyday athletes that have not been working with their fat adaptation and they are taking the gels in my take a while before they can actually access those, you know, fat stores.

fat stores. That's right. do need to be a good point, Marjaana. We need to go through a period of adaptation. And that can be a very frustrating time for people, especially if, you know, like me and you, Marjaana, I know, like it was, we were sort of down the road of being more carb adapted or sugar adapted. And we were very used to having that regular drip of glucose in our life.

to keep our glucose levels up to make us feel happy and energized. And you kind of have to go through that sad period where, you know, dopamine levels aren't as spiked all the time, right? You remember it wasn't too long ago for you. And yeah, like those are, you kind of, need to go through those periods of time and then make yourself believe that you can actually go for these longer periods of time without.

always dousing with a gel or whatever you take.

you

I think it was an exciting period. I think it was an exciting journey because you need to connect with the mind too. You have those doubts and questions, but I think it was exciting to see results without lots of sugar.

So what does it mean when the term is used metabolically flexible? What does that mean?

Yeah, super question. What it means is you can access either fats or carbohydrates. So if you're generally able to go without if you have to. this is like a perfect little survival sort of adaptation that you have. So say you're in the, if you're in the military, you want to be metabolically flexible because you never know when you're going to have to go without. Maybe you don't have a ration.

on your person and you have to go and perform something really important that's going to be life-saving for you or others. So you need to be metabolically flexible in that. Same for the athlete. You're metabolically flexible. You don't have to rely on that sugar. But all of a sudden you do have that available to you. You can also burn that carbohydrate. So if you're doing a race like an Ironman, like Marjaana's doing, even though she's mostly fat at

a fat adapted, she can still take on the gels on that course, take on coke, she switched to coke, midway through the bike, because that's what she knew she needed, and she could use both fuels. So it doesn't work the other way. It doesn't work where if you're carb adapted, you can't switch over quickly to the fat. But if you're fat adapted, you usually can switch back.

to the carbohydrate. So I think that's what it means. Does that make sense?

It does. So it's kind of like the best of both worlds in a lot of ways. You're fat adapted and then you can utilize the exogenous carbohydrate in order to fuel the effort that you're doing.

Correct, and that is also probably another important point is like, and some of us in the fat cult, let's call it, some of us get a little bit, go a little too far sometimes, and I put my hand up there as well, has been there in the past where we don't practice these carbohydrate amounts and needs.

And I think when you're getting towards the pointy end of your race in terms of the training and you're doing your key sets that are gonna prepare you for your race, it's a good idea to do these key sets in the fueled sort of status or situation, right? So imagine you're T minus one, two, three weeks out from your event. You better be fueling those key weekend sessions that are just pieces of the Ironman you're gonna do with

some carbohydrate just like you're gonna get on that day, at least in some form, so that you're practicing kind of the fueling and you know how that feels, right? So that's an important aspect of metabolic flexibility. You're just checking everything. You just make, yeah, that feels right. no, that's gonna be good on the day. So there's no surprises.

We have another question, this time from Robert. What are some objective measures to utilize when profiling athletes to assess the type of stimulus they would best respond to when tailoring training plans? For example, we have a novel ultra runner who is more of an anaerobic athlete thinking type three or four HIIT targets.

Mm-hmm. Okay, we'll get to the HIIT targets there in a sec, but let's just let's back the question up a bit. what Roberts probably taken our Pro, you know athlete profiling priming course because he's using those terms in there So Just a little plug out hundred percent free course go to athleteprofilingprimer.com and put in your email and you've got you know, you get a five-day course to teach you the basics of

profiling. And the long and the short of it is that we're all different profiles. We're all different in terms of our makeup, in terms of are we more slow twitch? You we can go long and strong for a long time, or are we more twitchy like a cheetah? We can absolutely fly and run and sprint super fast, or are we somewhere kind of in the middle? Now, Robert's question, he's wondering about, you know, hey, he's saying,

I'm a bit of an odd ultra runner. I'm more of a cheetah. I'm more of a, you know, I'm more of a sprinty kind of twitchy guy. Should I, what does that mean for me in terms of my, my hit sessions that are gonna compliment what it is that I, that I do in my training? And it's a great question. We have spoken, you know, we've spoken before on, the podcasts, training science podcasts about

the different types and what that means. So when you're doing HIIT sessions, like long intervals, when you do long intervals, we're talking like VO2 max intervals, things like a three minute effort with two minutes recovery repeat, you know, at VO2 max, those are really taxing on twitchy athletes because they, that fast twitch fiber that they use to gravitate on and do that high intensity work, it's not made of much mitochondria.

versus the diesel engine athlete that's doing that three minutes on, two minutes off, three minutes on, two minutes off at VO2 max. The fast twitch muscle fibers that they're using are more laden with mitochondria. They're more fatigue resistant and they don't push out as much lactate. And we know that the more lactate that you push out when you burn carbohydrates with those big powerful muscle fibers.

the more that stimulates the sympathetic nervous system, fight or flight system that causes for that stress. So this is how we're all different. So in Robert's case, if he's coaching or if he is an athlete that's got a real fast sprint, he wants to use short intervals because if he uses shorter intervals, and we're talking like the 30-30, the classic 30-30 that you see, but he could also be doing like

2040 as well, right? He needs that pause in between his sprinty efforts. When he takes that pause, short pause in between the sprinty efforts, we have this cool little molecule called myoglobin, which is the hemoglobin of your muscles and it quickly resaturates the oxygen and it blunts the lactate response in those twitchy athletes. So if we switch things over,

once they're over, how much focus and the balance to right from the beginning is yeah.

You know, as coaches think about this too, right? If you know you got a twitchy athlete, switch it over to do short intervals and you're going to get a lot better response. We're not going to push out lactate as much. We're not going to stimulate that athlete's sympathetic nervous system as much. And they'll be able to remember, they'll be able to continue on the next time with that consistent training. Remember consistency in training is one of the key, key factors that's going to lead to.

Thank

Thank

to performance success or building your fitness profile. And the last part, mean, Robert's getting fancy here and you can see he's well-read in hit science. Thank you, Robert. He's talking type three and type four targets. These are basically anaerobic and anaerobic with...

A neuromuscular target. Thank you, Paul. Yes. Saw the book there. So, yeah. So, Robert is thinking right, but use the short interval, right? So, those are the right targets, Robert, but use the short interval format or weapon to get at that target.

Yep, that's where it's from.

I think also important to consider how often he does the high intensity interval work.

Yeah, mean, how long is a piece of string? It really depends on how conditioned you are to it. Probably also depends on your phenotype, what we just talked about. But, know, five days is kind of, you know, a general good rule. You know, one at least sort of have probably five days between them, especially if you're giving kind of a solid effort.

And as one example, Marjaana runs her short interval work as a group on Zwift and she's doing that every week, every seven days, right? So you can go more frequent, especially the more well-trained you are, but as a general rule, you're usually pretty ready for another hit of some sort, pardon the pun, after about five days.

All right, next question is from Adam Evans. Why do overtraining warnings appear on Athletica's training plan? One popped up on a session for next week, but now it's gone. What's the best way to deal with them? Shouldn't the program automatically adjust to not create overtraining?

Yeah, we get this one a lot, don't we, MJ?

All the time, yeah.

All the time.

are just guidelines. So a couple things. We have dealt with this question again, but it's good that they're there. And we've talked about just absolutely removing these. There is, I will say, if these are annoying you as an athlete on Athletica, just go to your settings in your profile, and there's just a little place in your profile settings, and you just click.

remove warnings from Athletica and those will go away. All it's there for you is a little bit of a guideline to say, this is looking back to your performance profile. And Andrea Zignoli spoke about the performance profile. He spoke about the Bannister model, fitness and fatigue and how Athletica uses markers of that

power, pace and heart rate that you are, that you're recording and giving to Athletica. And it's sensing how much training load, remember training load is another word for training stress. So basically it's saying that, you you're looking like you're getting quite a bit of stress in your workout and your workouts that have been before that. And, you know, we might, you know, there will be changes that were made, that are being made.

So just check on that. You should have these, you should see your workouts actually adapting. And if you look downstream of your sessions, you'll see a before and after. But sometimes it gets to the point where there's so much load training that's going on that, know, Athletica kind of can't put too much less on that. So therefore it sort of shows you this over training warning.

But it's just a warning, it's just saying, hey, we see you're working pretty hard out there. Keep in mind, you're pushing it. Just be mindful of it. You might wanna grab a workout and move it downstream, delete a workout, especially if it feels right. Mostly you should be acting on these warnings when they align with your feeling. Are you losing, are you sleeping bad?

Do you really feel like you are actually over training? Because if you are, then you've got more than one indicator, right? HRV is another one, is your HRV tanking, right? So all of these various different things, they're just indicators to say, let's have a think of the whole program and what would be a wise decision right now.

And yeah, and you make a great point, Adam, with respect to should Athletica actually move this. This is something that we're looking at in the future. It might be an option for people in the future, but we're, Andrea spoke to this and one of our key philosophies is that we really want to work alongside you as an athlete or you as a coach to give you this advice. because we all, big, big philosophy is that the context rules over the content.

You know more than we do. You know more than Athletica does. You know, as we spoke to just recently with Alan, there's a learning curve about that. know that's, but you know, we're on this journey with you and we know that you can learn what feels like good training. So stick with it. It's worth it. And these warnings are just there as your friend to keep you in line.

feel free to voice your comments on the forum, get in touch with us.

We're usually pretty helpful and fairly responsive when we get these emails and messages. So I think I answered some of those there. But any further, Marjaana

Have a good one.

I also get them every once in a while. It's kind of a fine balance what you do with those. But they can be really helpful teaching you about the feel. I know like we've talked about the feel so many times, but it's maybe not very clear what it means if you've never thought of.

your bodies and minds response to hard training.

And those overtraining warnings can help you like center and ground yourself and like, like put all those pieces together, your sleep, your stress, your overall energy, and then make those adjustments. It's like if you think of Athletica as a GPS unit and you just drive a little too far,

You know, you missed your turn. The overtraining warning is kind of like, hey, I think you just missed your turn. I'll reroute, right? So if you see those, maybe it's time to like really center and ground yourself and ask, hey, if I go run now.

will my legs just feel like two blocks of wood? And how long do they feel like you're running through mud or whatever? So I think they can be really helpful.

All right, we have one more question and this is from Georgio Patsiolis. I think we've answered his question before. And in a previous podcast, I think it was episode 27, we talked about the benefits of training in the heat.

He's asking how we can measure this, for example, with core sensor and are these tools compatible with Athetica?

Not yet, Giorgio. So yeah, we're definitely keeping an eye on Core. And Core, to my knowledge, it's basically a skin sensor. It sits on your heart rate monitor, I believe, that's just touching your skin. And yeah, it's one site, to my knowledge. And it's giving an indicator of what your core temperature might be based on that.

you know, that's cool, but at the end of the day, it's not compatible yet and we'll keep an eye on it. Again, I would encourage Giorgio to go back and listen to the podcast that we've done on heat to listen to the podcast that I've done with Chris Mintzen on heat adaptation on the Training Science Podcast. It another fantastic one, but you know, ultimately, you

Getting heat in your program is so beneficial and you can get it in your program in so many different ways. But yeah, there's a lot of different adaptations that occur when we get hot. And I know, Marjaana, you're big convert as well, having recently used heat adaptation for your Ironman.

And, but the general principle is get hot in your workouts and outside of your workouts. If you're in a cold climate like I'm in, you know, going, so I'll, you know, I'll be doing a lot of saunas and whatnot. And I know I get a, keeps my cardiovascular system running pretty smoothly. So the workouts actually feel a lot easier when I'm doing heat training all along those ones.

It's hard. There's really no objective measures to say, hey, now I know that I'm heat-adapted, but I just kept track of my running time. So in the beginning, it would be a lot slower than in a cooler weather running.

And then after a while... And it would feel so horrible.

I hated it. We've talked about it many times. So it's so hard. So there's two things that I kept track of. My overall feel when I was running in the heat and how long I was like somewhat okay running. So first it was maybe half an hour, then it was 45 minutes.

Mmm.

Then it was like an hour, it was fine before I felt like dying. And then the second measure was my running speed. So on my Arabic runs, I would just keep track of my run pace. So first it was slow and then it started to pick up and eventually got to the same running pace as my cold weather.

Yeah, perfect. And then the other thing you can look at as well as your heart rate, of course. So you're looking at your efficiency, your aerobic deep coupling. all of these ones should be improving as well. So you should be running at the same or lower heart rate as in the cool prior. And that should just start to plateau the more heat adapted that you get.

So.

Yeah.

And that's because of all these various different changes that are occurring in your body where your cardiovascular efficiency ultimately is improving and your plasma volume is expanding, the sodium kinetics of your body are improving and all these various different things that we've spoken about previously, but it's super beneficial to get in you and a lot does come down to feel.

and putting it super simple, you should feel a whole lot better in the heat after heat training than you did when you started doing it.

Simple enough. there are so many devices that are coming out that are still truly in their infancy with continuous glucose monitors and lactate monitors and core temperature monitors. they're just not there yet in my eyes. And they're getting closer. They're getting more usable, but not fully yet.

Yeah. And this probably in my mind, this is really where the, you know, the help of a coach that uses a program like Athletica. So someone like Paul and Marjaana is super beneficial because they, you know, people like that are experienced at it and they can walk you through that, developing that feel. And it's really, you know, I just encourage, encourage any listeners there that are wondering about this to, to reach out to the two of you to,

Mm-hmm.

to use your services to help you.

Thank you. Well, that is all for this week. We had four solid, interesting questions. Join us next week on the Athletes Compass podcast. Again, ask these training questions, you know, on our Facebook, in the comments, in the forum, on our social media. If you enjoyed this episode, we'd appreciate it if you could take a moment to give us a follow and a five-star review. For more information or to schedule a consultation with Paul, Marjaana or myself,

check the links in the show notes for Marjaana Rakai Dr. Paul Laursen I'm Paul Warloski and this has been the athletes compass podcast. Thank you for listening.