I want to talk about the concept of aerobic deficiency—something that is very common, even amongst very fit, high-performing athletes.

Aerobic deficiency (a term coined by Dr. Phil Maffetone), or anaerobic excess, means that while you’ve developed tremendous performance skills, the capacity of the aerobic system is lacking due to insufficient aerobic conditioning/workouts. So while you are good for short bursts of power, your overall athletic potential is limited by insufficient development of the aerobic system.

As you will hear in this show, it’s important to remember that even the most explosive, powerful athletes require sufficient aerobic conditioning in order to thrive in the long duration workouts that they perform in order to hone their abilities so they can compete in activities like powerlifting and sprinting. If you are the type of person who will go out to sprint practice for an hour or even up to two hours, this is an episode you don’t want to miss. As you’ll learn, even if you are also stretching and resting throughout that practice session, the aerobic system is still working for the entire duration of the workout—the same concept applies to going to the gym to perform heavy weight lifting sessions.

If you want to learn how to sufficiently develop your aerobic system, this episode will walk you through every step and teach you how to do it.


Aerobic deficiency is very common even among very fit, powerful high-performing athletes. [00:38]

The aerobic system contributes very much to even very short duration efforts. [04:01]

A 50 50 ratio of aerobic to anaerobic contribution to your energy needs is a minute and 15 seconds all-out performance. [06:23]

When we truly conduct a fat-burning workout that emphasizes aerobic development and minimizes anaerobic stimulation, it is frustratingly slow in many cases.  [10:25]

At Fat Max you are burning maximum fat minimum glucose and as you speed up, fat burning goes down and sugar burning spikes. [13:43]

Fat Max is 180 minus your age in beats per minute.  You want to have the same exact course, doing the same exact test every time. [17:01]

Eluid Kipchoge trains at a very slow comfortable pace. [21:18]



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Brad (00:00):
Welcome to the B.rad podcast, where we explore ways to pursue peak performance with passion throughout life without taking ourselves too seriously. I’m Brad Kearns, New York Times bestselling author, former number three, world-ranked professional triathlete and Guinness World Record Masters athlete. I connect with experts in diet, fitness, and personal growth, and deliver short breather shows where you get simple actionable tips to improve your life right away. Let’s explore beyond the hype hacks, shortcuts, and sciencey talk to laugh, have fun, and appreciate the journey. It’s time to B.rad.

Brad (00:38):
Here is the challenge, possibly the frustration for most of us. I wanna talk about the concept of aerobic deficiency, which is very common, even amongst very fit, powerful, high performing athletes. And this is a concept, a term coined by Dr. Phil Maffetone. Aerobic deficiency slash anaerobic excess. So you have developed tremendous athletic skills to perform, to jump out at the gym and dunk the basketball or lift heavy weights. But underneath the, uh, the, the capacity of the aerobic system is lacking due to insufficient aerobic conditioning, aerobic workouts such that you are good for short bursts of power, but your overall athletic potential is limited by insufficient development of the aerobic system. And it’s important to remember that even the most explosive, powerful athletes require sufficient aerobic conditioning in order to, uh, thrive in the long duration workouts that they are, uh, performing to hone their ability to, for example, compete in power lifting or compete in sprinting.

Brad (01:57):
Um, if you’re going out to sprint practice that lasts for an hour or possibly two hours, a lot of recovery time, a lot of walking and, and stretching and doing drills and resting a lot. However, the aerobic system is working for the entire duration of the workout. Same with doing sets of heavy weightlifting in the gym. As soon as you get out of your car and walk to the the gym, your aerobic system is kicking into gear to, uh, nurture and fuel your performance. And your heart rate is probably at least double resting heart rate for the entire duration of your, uh, parking, the car, uh, walking to the gym, doing, uh, brief, uh, cardio warmup on the bicycle, and then hitting the heavy weights. Or perhaps you’re going to play pickup basketball where you’re sitting around waiting for your turn on the court, doing dribbling drills.

Brad (02:52):
doing light exercise, uh, pacing around your aerobic system is kicking into gear this whole time, especially on the court, when you’re doing brief bursts of anaerobic effort, such as on a play, then the whistle blows, then you have recovery time. But your aerobic system underneath everything is the base for all manner of fitness and athletic performance. Because the aerobic system nurtures the functioning of the explosive short duration anaerobic system. The anaerobic muscle fibers and the aerobic muscle fibers are intertwined in the muscles. The anaerobic muscle fibers perform brief explosive efforts without oxygen, but in order for them to recover and regenerate a TP and remove waste products, they require the highly oxygenated and efficient aerobic system to help them perform and recover. So it’s not a black and white case where if you like explosive high performance sports like football, basketball, uh, power lifting, sprinting, whatever, that you don’t need to engage in aerobic exercise.

Brad (04:01):
This is something I think is coming up frequently with the so-called hybrid athlete of today, where the goal is to, you know, develop a comprehensive full-body functional fitness for not just power and strength and explosiveness, but also endurance. And I marvel at the amazing performances of these athletes. Some of the most graphic examples are where there’s a challenge to deadlift 500 pounds and then go run a sub five minute mile. There’s people that are doing amazing deadlift performances and then heading out and running 30 miles. Of course, CrossFit is modeled after this ambition to they call it Forg Elite Fitness, where you’re developing disparate skills such as becoming competent at Olympic lifting and explosive sets of body weight exercises or, box jumps or rope climbs, and being able to run around the block and return and jump on the assault bike and do something that amounts to overall a challenging endurance performance.

Brad (05:14):
Because the CrossFit session is 50 minutes in duration, or the CrossFit Games competition where they’re going through repeated sets of extremely difficult high intensity exercise. But it’s lasting for 12, 15 or 20 minutes. And when we talk about the distinction between explosive, high performance anaerobic efforts and aerobic efforts, usually we think of aerobic as going out for a jog at a slow pace or bicycling for 40 miles, that’s aerobic. And then anaerobic is everything else shorter. But with the exercise physiology insights that are mind-blowing to me when I first learned these just how much the aerobic system contributes even to very short duration efforts. And so when we are measuring this in laboratory. This is research from Dr. Gaston, reporting that, of course a effort of, seven seconds or less, a maximum all-out effort of seven seconds or less is fueled by pure ATP in the muscle cell.

Brad (06:23):
So it’s 100% anaerobic. You don’t even need to breathe if you’re running the 40 yard dash for the NFL combine or doing the 60 meter indoors indoor track and field. And so that’s a hundred percent anaerobic. And then as you start to get up to, for example, an all out effort of 30 seconds or less, you are engaging in a combination of aerobic and anaerobic glycolysis. So you are starting to call into action the aerobic system, uh, the oxygenating system, even for very short sprint effort. Now, a 50 50 ratio of aerobic to anaerobic contribution to your energy needs is a minute, 15 seconds all-out performance. Isn’t that amazing? That’s just a very short duration, for example, track and field event or a swimming event where it seems like a sprint. It is a sprint. The athletes are going very fast, but that is a 50% aerobic and 50% anaerobic effort.

Brad (07:24):
Now, when you get up to something like the Mile and the world’s great milers like Jakob Ingerbrigsten, and Yara Nago, and the guys who are well under four minutes. The mile is 79% aerobic. So an all out effort of around five minutes in duration is predominantly aerobic, even though you are moving very quickly, breathing very hard and calling into action, a lot of anaerobic performance too, 20% contribution, anaerobic, 79% aerobic. So the concept here is that even when you’re going really hard for a short time, like a minute 15 or a a five minute effort, it’s predominantly aerobic at five minutes. It’s so mind blowing. This is why the world’s leading milers are running in excess of 100 miles a week in their training to perform in an event that lasts for only under four minutes. Same with the swimmers. You saw Michael Phelps win his 28 gold medals over numerous Olympics.

Brad (08:24):
And the duration of his swim events lasted from 51 seconds up to like four minutes where he was doing the, um, the, the IM 51 would be like a sprint, a hundred meter, and he was competent at so many different events. That’s how he bagged all those gold medals. But for those events lasting between 51 seconds and four minutes at the most, Michael Phelps was training five to six hours a day for numerous decades. So underneath the performances of even the high performing athletes at short duration events, they are putting in a ton of aerobic conditioning. Reference my great interview with my old triathlon buddy, Chris Hinshaw, who’s now a prominent coach, especially in the CrossFit community, and his concept of aerobic capacity. That’s the name of his social media and website. So you can look up his aerobic capacity movement.

Brad (09:20):
He came in to CrossFit over a decade ago and realized that there was a huge deficiency in the training protocols of the leading athletes. He has now coached 50 CrossFit games champions, with this underpinning of performing sufficient low intensity exercise to nurture and develop and improve the aerobic system so that the explosive high performance anaerobic efforts would be better tolerated and improve one’s ceiling one’s potential. So that if you can raise your aerobic capacity or your aerobic base, raise the platform from which you launch all efforts of high speed, that’s why the milers are building that base and running a hundred miles a week with a lot of comfortably paced training in order to step on the track and be able to handle extremely fast pace for this, sub four minute event.

Brad (10:25):
And all those hybrid athletes out there. I suspect that with all that explosive high intensity workouts that they’re doing in the gym and elsewhere a lot of times they’re heading out and jogging and have a sufficient level of fitness to go out there and run six minute miles, seven minute miles, whatever they’re doing. But they’re exceeding their Fat Max heart rate or their aerobic limit and going into this no man’s land where the workout is a little bit too strenuous to truly nurture and develop the aerobic system, the mitochondrial biogenesis, and all the great things that happen when you teach your body to burn fat efficiently at comfortable heart rates. So here is the challenge, possibly the frustration for most of us when we truly conduct a predominantly fat burning workout that emphasizes aerobic development and minimizes anaerobic stimulation. Uh, it’s, it’s frustratingly slow in many cases.

Brad (11:29):
So the objective here is if you want to develop your aerobic capacity and nurture your aerobic systems so that you can perform better, even in explosive high intensity efforts. And hey, if your goals are more endurance oriented, so you wanna perform in the 5K or the 10 k or the half marathon, or the really long distance stuff that is almost entirely aerobic, a one hour effort all out time trial, they would call it an anaerobic threshold effort that represents something that’s 98% contribution of the aerobic system and only 2% of anaerobic metabolism. So you have sufficient oxygen to perform for an, uh, one hour time trial. That’s kind of a, a revelation to a lot of people too, who think that they have to work that top end speed frequently if they want to be able to go fast for an hour.

Brad (12:22):
But the best way to perform and reach a potential even on efforts that are, you know, 15 minutes, 20 minutes, 30 minutes or an hour, is to develop at that Fat Max heart rate or below, or well below you get a tremendous aerobic stimulation without the risk of burnout breakdown and, uh, extended fatigue and recovery time when you perform well below Fat Max heart rate. Most people are really frustrated to hear that beeper alarm go off when they hit Fat Max, and they don’t even realize that if you slow down even further, you get great training. This is how the elite athletes in every endurance sport have performed and have trained for the last 60 years. Dating back to Arthur Lydiard, the great coach in New Zealand who developed the runners that stormed the world stage starting in 1960 and won a bunch of gold medals in the middle distance and long distance events in the Olympics, the tiny country of New Zealand just became the dominant power, thanks in large part to Arthur Lydiard’s novel training methods where he had his endurance and middle distance runners doing a lot of over distance, comfortably paced exercise in order to perform well at distances as short as 800 meters.

Brad (13:43):
And so when we talk about Fat Max you’ve heard me on, on numerous shows emphasize this important point, the calculation. This is the Maffetone formula, widely respected to be a accurate, estimation of your Fat Max heart rate. Something that you can identify accurately in laboratory tests like the VO two max tests that are very popular now in clinics and gyms. And you can go pay 80 or a hundred bucks and get your, get your mask on your face, breathe into the gas exchange meter, and they’ll tell you all your levels for your anaerobic threshold. And what’s often called aerobic threshold or Fat Max that’s a similar thing where you’re burning the maximum number of fat calories per minute with a minimum amount of anaerobic stimulation. So Fat Max is the maximum fat burning, and if you were to speed up from that pace, you would of course burn more total calories per minute.

Brad (14:43):
The faster you go, the more calories you burn, right? But on a graph, this would be represented by a decrease in the number of fat calories burned per minute, and a huge spike or a comparatively huge spike in the number of glucose calories burned per minute. So, at Fat Max you’re burning maximum fat minimum glucose. And as you speed up fat burning goes down and sugar burning spikes, how can you identify this roughly? Well, if you start to become a little bit out of breath, that is a reliable indicator that you are passing up your Fat Max, where you have plenty of oxygen to emphasize fat burning and drifting into these heart rates that make it a little more difficult to supply sufficient ATP through predominantly fat metabolism. And now you have to kick into glucose metabolism. And of course, all kinds of workouts have training effects and adaptations. But the problem is, when you frequently exceed Fat Max heart rate, you become aerobically deficient and develop your anaerobic capacity to excess. And when you engage in this type of training pattern, what you are essentially doing is bypassing the foundational work necessary to reach your overall competitive potential. And instead, you are fine tuning a smaller engine. You’re fine tuning a jalopy rather than taking the time to patiently build a Ferrari engine that will perform better at all higher levels of exercise intensity because you are so competent at burning fat and the way to track your improvement and your progress here. And, uh, the way that to identify that you’re doing it correctly is to perform a maximum aerobic function test frequently. And the math test, MAF stands for Maffetone. He invented the test is where you go out and track your performance at that Fat Max heart rate, and then over time expect to be able to go faster while still maintaining a predominantly fat burning metabolic state.

Brad (17:01):
So for a simple example, you want to have the same exact course, the same exact test every time, and pegging your heart rate as as good as you possibly can. Obviously you’re exercising, the heart rate’s gonna bounce around, but if you get a little too high, you take it back down. If you’re going too slow, you just try to peg it as close as you can to your Fat Max number. And remember, Fat Max is 180 minus your age in beats per minute, 180 minus age in beats per minute in Dr. Maffetone’s books. And on his website, he has a variety of adjustment factors to help individualize it further. So if you’re coming off injuries struggles, you’re gonna be able, you’re gonna have to subtract five from your number to get an accurate Fat Max heart rate. If you’re taking prescription medication, uh, had numerous setbacks in recent times, you want to go conservative, you always want to err on the conservative side with Fat Max training.

Brad (18:01):
And on certain occasions, if you’ve been really successful or you’re an older age group athlete like myself, where my maximum heart rate is not declining at the predicted rate is declining, uh, slower than that. So I’m allowed to add five beats to my Fat Max heart rate. But in general, 180 minus your age, so 40-year-old athlete, 180 minus 40 Fat Max heart rate would be 140 beats per minute. So you set your beeper alarm on your watch and you take off down the road, whether you’re pedaling or jogging or whatever, and whatever pace that correlates to, that’s the pace where you will develop your aerobic system with most benefit and least risk of overdoing it and kicking into anaerobic metabolism. And as you patiently, uh, work in these heart rate zones, that’s when you can notice a steady improvement in your MAF test results.

Brad (18:59):
So if you go to, for example, a running track and your fatmax test is, uh, running four laps, close to a mile, most tracks are 400 meters. So it’s really 1,609 meters. So you do four laps and then another 10 meters to get an accurate mile test. And that’s important for marathon runners. ’cause you can calculate optimal marathon pace off of your Fat Max result. It’s actually 15 seconds per mile faster than your Fat Max pace. So the Fat Max test is super comfortable. It’s not strenuous at all. You can repeat it frequently, but basically you, you set off down the track, try to get that heart rate up at around 140 and keep it there for all four laps. You cross the finish line, you check your time. So if your first test is 13 minutes and 20 seconds, you’re ploting along keeping that heart rate 139, 141, 140, 138, 141, 140.

Brad (19:56):
Whatever you do to keep it there, note your time. And then as you continue to build your aerobic system, you will expect to go back to the track, run the same four laps, and here comes a finishing time of 12:47, 12:30, 12:18. And a lot of people report a steady improvement and even dramatic improvement if you have the patience to develop your aerobic capacity properly by exercising, emphasizing, uh, the endurance workouts at those lower heart rates. And just for reference, the, the world’s lead athletes are doing a vast majority of their training at or below or well below Fat Max heart rate because the fritter you get and the faster you’re able to go at Fat Max heart rate, uh, it warrants that you can’t put in a ton of mileage running at a six minute pace. Or like the great, uh, marathoner Eluid Kipchoge, um, they scrutinized his training log, he published his training log for all the world to review and the exercise physiologists and coaches had a field day studying all this stuff and concluding that he runs 82 to 84% of his weekly mileage at what is designated as quote, easy pace or 50% capacity pace.

Brad (21:18):
So here’s the greatest runner, the greatest marathon runner, one of the greatest endurance athletes who’s ever walked on planet Earth. And he trains relatively easier than the average recreational enthusiast who is up pegging against fat mat, Fat Max heart rate, or generally, uh, exceeding it, uh, routinely during workouts. So if the greatest runner in the world is running 82 to 84% of the time at a very comfortable heart rate that is well below, uh, or well slower than his marathon race pace, this is something that we all should model and perhaps even model more so than the most genetically gifted fittest athlete who’s dedicated his entire life to, uh, racing the marathon fast. He’s the guy who ran a 1:59 marathon in the staged event, and, um, that represents a pace of four minutes and 34 seconds per mile for a marathon race. One of the greatest human achievements, just absolutely stunning, but he does 82 to 84% of his weekly mileage at a pace per mile of 6:26 to 8:04.

Brad (22:27):
Yep, that’s pretty freaking impressive. But for him, it’s pretty incredibly slow. So if you extrapolate that to your current marathon capabilities and the average marathon finisher across the world comes in at four hours and 30 minutes, that’s the most recent statistics that represents a pace of, I believe, 10 minutes, 18 seconds per mile. So if you’re running, I believe it’s a 28 to 43% slower than your marathon pace is what Kipchoge is doing. We are talking about doing the vast majority, 82 to 84% of all your training at pace per mile up there in the 12 or 13 or 14 minute pace. And yes, we also know from gait analysis, exercise physiology that the crossover point for most humans to transition from a walk to a jog is 14 minutes per mile. In other words, if you’re going slower than 14 minute mile, you are now walking rather than jogging.

Brad (23:28):
This is a vote for spending more time doing easy to medium, to brisk walking as part of your training program for peak performance in marathon half marathon, 5K, 10K unless you’re extremely fit, even an easy jog will likely get that beeper alarm going in my example of 140 beats per minute because it’s a very, very comfortable pace. And if you can jog at, you know, seven minute pace per mile at your Fat Max or six minute pace per mile, you are one of the fastest people in the entire pack of marathon runners. For most people, most of their training should be something like a brisk walk or maybe a very slow jog if they’re super fit. And of course, we can apply this to all other aerobic cardiovascular activity. So if you’re a bicyclist and you want to go faster in your next century ride or your race, you’re gonna be doing a lot of easy pedaling as evidence by the training methods of the greatest cyclists on the planet, the Tour de France riders who, yep, they train 4 or 5, 6, 7 hours a day, but they’re well within their aerobic capacity for the vast majority of their pedaling.

Brad (24:46):
Again, take that example of Kipchoge, take it to heart because if the greatest athlete on the planet is doing most of his training at a very comfortable pace, you should too. There’s absolutely no exceptions to this except for if you’re not that fit <laugh>maybe you’re gonna do 90% of your exercise at what’s considered an easy or a very low capacity pace. And I promise you, you will develop and you’ll develop further, and you’ll develop further to the point where if you go and do a maximum aerobic function test now and your pace is your mild test is 14 minutes. In other words, that’s a brisk walk. In a six weeks time or six months time, you’re gonna get down to 13:20 and 12:57 and 12:48 and 12:17 someday. So you’re gonna switch as an athlete, you’re gonna switch from an aerobic walker to an aerobic jogger, and that represents a phenomenal, uh, improvement in overall conditioning and competitive potential because if you can jog a mile in 12:18 at your Fat Max heart rate, that suggests that you can run seven minute, eight minute pace for a 10K or for whatever your competitive interest is.

Brad (26:07):
And again, I mentioned the, uh, optimal marathon pace. This is also research from Maffetone is around 15 seconds per mile faster than your one mile maximum aerobic function test result. So if you can get your MAF test or result down to 12 minutes for one mile at Fatmax heart rate, you can go out there and aspire to run a marathon at 1145 pace. Okay? the other thing I wanna mention is, um, when I was in my most devoted endurance training when I was professional triathlete racing for nine years on the pro circuit, I did the vast majority of my training well being low, my Fat Max heart rate. Back then I was a young person, my Fat Max was 155 beats per minute. And so most of my running workouts were 25 to 40 beats being low, my Fat Max.

Brad (27:05):
So that would be 110 to 130 or so. Yeah. And at this time, my aerobic capacity was, you know, excellent. So I could run on my maximum aerobic function test, I would do longer tests because my goal was competing in, uh, two hour long triathlons. I could run five miles in 30 minutes at my Fat Max pace. That’s a six minute pace per mile at 1 55 beats per minute. Of course my competitive potential was much better than that. When I’m out there doing a 10 K race, I could run around five minutes per mile, but my Fat Max pace was a six minute mile. So when I was training, I’m running 7:30s eight minute pace. I’m putting in a lot of time on my feet at heart rates that are way below Fat Max. Now let’s translate that to today.

Brad (27:58):
Where I’m an old guy, I’m not training all day and my aerobic capacity is much lower. My VO2 max and all those things are much lower. If I took a workout at 25 to 40 beats below my Fat Max heart rate, it would be a brisk walk, even though I’m still in pretty decent shape and I could probably run a pretty fast single mile if I had to race, you know, six minute mile or something, maybe a little below that. But the proper way to train and build the aerobic system is all requisite on your relative fitness at any time. So when I was performing at my best, I was doing a lot of mileage at 25 to 40 beats below Fat Max. Therefore, I should still do the same today, which means in the Kipchoge example again, that 82 to 84% of my aerobic conditioning would best be at a middle or brisk walk rather than even jogging.

Brad (28:55):
I know this is super tough to swallow and it was super tough for me to transition away from this struggle and suffer mentality where I was so competitive and so disciplined and I wanted to do whatever it took to be the fastest triathlete and be ranked on the circuit and win races. And so I would train and train and train my heart out. And then I remember about halfway through my career, excuse me, I became extremely frustrated because guys were still kicking my butt even though I was training as hard as I could. And I remember cornering the Grip Mark Allen former podcast guest, the greatest triathlete of all time, one of the greatest endurance athletes of all time. cxI remember cornering him after a race in desperation. I said, Mark, what’s going on? I’m a young, hardworking, talented athlete. I’m training as hard as I can.

Brad (29:49):
I’m dedicating every ounce of my energy and devoting my life to this sport, and I’m still getting my ass kicked by the likes of you. What’s going on? And he says, you have to slow down. You have to build your aerobic capacity. You have to take better care of your body and not push yourself too hard with these challenging strenuous workouts. You have to build that aerobic base and improve that aerobic base carefully over time without the interruption caused by training too hard and frying your system, frying your muscular skeletal system, your hormonal, your endocrine system from these, uh, long duration workouts that were too strenuous. And that was the turning point. He inspired me to connect with Maffetone, who was helping some of the other great athletes at the time. And the whole message was slow down to go faster. And that’s what the primal endurance approach that Mark Sisson and I developed is all about.

Brad (30:44):
You can look at PrimalEndurance.fit and sign up for the comprehensive online multimedia course, the most comprehensive course on endurance training ever developed in the world. It’s such a great experience to get all these interviews from the greatest athletes, coaches, experts in endurance training. And it will transform your life. It will change your approach to be one that’s less strenuous, more enjoyable, and more successful on the race course. So it’s all about slowing down, disciplining that unregulated competitive intensity and allowing yourself to develop the aerobic system naturally at those comfortable heart rates. Realizing, as I talked about at the outset, that it will improve your performance even at the most explosive short duration efforts like sprinting, like power lifting, and all the, uh, the protocol of the CrossFit games and other such challenges. So aerobic capacity is essential for all athletes.

Brad (31:45):
I invite you to explore this further Primal Endurance stuff. It also has a free mini course where I cover some of these in a series of videos to give you a little, uh, tidbit of, uh, what’s to come. Of course the book goes into detail too, and you can get that book on Amazon still. But I recommend the digital course, the book, if you’re a fan of endurance training, you gotta do it the right way. Otherwise it’s so strenuous and exhausting that it’ll just be one frustration after another. That’s my plug for slowing down to go faster. Thank you so much for listening. watching this oftentimes generates a lot of comments and questions, so please engage with us, podcast@bradventures.com and let me know what you think. Lemme know how it’s worked for you and I look forward to hearing from you. Thank you. Thank you so much for listening to the B.rad Podcast. We appreciate all feedback and suggestions.

Brad (32:38):
Email podcast@bradventures.com and visit BradKearns.com to download five free eBooks and learn some great long cuts to a longer life. How to optimize testosterone naturally, become a dark chocolate connoisseur and transition to a barefoot and minimalist shoe lifestyle.


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