Dear Heat,

It’s over. 

I’ve been sweating this relationship for way too long and enough is enough.

I used to look forward to being with you – especially in the summer. But that all changed once we started working out together. You became excessive to the point of exhaustion. “I’ll help you detox!”, you said. Well guess what, buddy? That’s what my kidneys and liver are for. 

Also, you make everything smell so bad. Trust me, if I wanted to smell like garbage all the time, I’d move to Staten Island. And speaking of trash talking, the times that you took my breath away had nothing to do with you being romantic.  

Truth is, I deserve to be in a healthy relationship with someone who doesn’t steal my energy or act like a hot-head all the time. I need someone more chill, a partner that gives me goosebumps when I’m around them – not an itchy rash. 

So goodbye, Heat. May the shoulder that you cry on be as cold as my heart.

Thankfully not yours,

Your Ex



Why You Should Warm Up to Cooler Temperatures

Mild Cold Stress

This refers to the physiological responses that the human body experiences when exposed to temperatures between 40°-64°F. The cold acts as a natural stressor on the body to which it has to react.

If there’s anything you retain from our accordion list of cool facts, let it be this, your first rule of Brrrn Club (insert Fight Club joke): You don’t talk about stress unless you’re talking about mild cold stress.

But seriously, if you were in a room chilled to 60°F with only a bathing suit on, you would no longer be able to rely on an outside heat source to ensure your body stays at 98.6°F. Instead, your body would have to rely on its own inner heat, aka, your metabolism – the sum of your trillions of cells working together — to keep you heated.

Keep in mind, variables such your very own body fat, genetic composition, age, satiation level and experience in cooler temperatures affects your comfort threshold and how your body responds to this cooler environment.

Case in point, cool environments can elicit a response on our bodies and there are some pretty cool health benefits involved when this happens, such as burning more calories, and building a higher tolerance to colder environments.

To learn more, check out these papers:

The “Metabolic Winter” Hypothesis: A Cause of the Current Epidemics of Obesity and Cardiometabolic Disease

Cold exposure – an approach to increasing energy expenditure in humans

Mild cold induced thermogenesis: are BAT and skeletal muscle synergistic partners?

Cold acclimation recruits human brown fat and increases nonshivering thermogenesis

Collection of Cold Stress Papers by Dutch Researcher Dr. Wouter D. Van Marken Lichtenbelt, Ph.D., at Maastricht University in The Netherlands in the Department of Ecologic Energetics and Health

Recruited brown adipose tissue as an antiobesity agent in humans

Involvement of basal metabolic rate in determination of type of cold tolerance

The Lower East Side circa 1905

Do you think the folks living on Orchard Street in New York City’s Lower East Side in the early 1900’s woke up in their apartments to a perfectly manicured temperature of 72°F in fall, winter, spring and summer?

They didn’t

It was cold in their dwellings in the cooler months. And how do we know this? Um, we took the Tenement Museum tour because learning is cool.

Their indoor temperatures would only rise once breakfast was made—probably offals (intestines of animals), root vegetables, a simple grain – using a coal or wood stove that heated the entire apartment. And if they lived on a top floor, they were lucky in winter and unlucky in summer.

So the next time a little chill is in the air, have a little perspective on how hard it was for the women and men that came before you.

The Thermal Comfort Zone

Our thermal comfort zone refers to the temperature at which you feel the most comfortable. It’s the temperature your body has to exert the least amount of effort to operate and keep you at 98.6°F.

Remember, your body wants to burn the least amount of calories at all times because it thinks winter or a famine is coming. Like, literally all the time.

We seek our thermal comfort zone the same way that Goldilocks did her porridge. And that “just right” temperature range is largely dependent on factors such as your age, gender, body composition, satiation levels and even the number of layers of clothing that you have on.

All these factors affect whether you feel cold at 72°F or 68°F.

In recent decades, researchers have been noticing a trend in that people like it warmer. What does this mean? It means that instead of our bodies doing the work to keep us at 98.6°F, we are relying on outside sources of technology and engineering to do the work for us. And in our opinion, these modern advancements in sourcing heat come with unintended consequences.

Honestly, the best way to feel heated year-round in New York City is to ride the subway during rush hour.

To learn more about this topic, explore these studies:

Differences between young adults and elderly in thermal comfort, productivity, and thermal physiology in response to a moderate temperature drift and a steady-state conditio.

Four‐week cold acclimation in adult humans shifts uncoupling thermogenesis from skeletal muscles to brown adipose tissue

Burn More Calories in Cold

Spoiler alert: You can burn more calories in cold. End of story.

What happens when you go outside in only your underwear in the middle of January in Wisconsin? You shiver. You might jump up and down or do the dance of joy. While this is happening, your metabolism is revving way-up because the clothing you left inside is no longer on you. Your body has no choice but to use its own internal means to keep you warm: your metabolism.

It is because of this fact that co-founder Jimmy named the company Brrrn: a play on words between the temperature and the primary benefit of working out in cooler temperatures is indeed burning more calories.

As pertains to burning more calories while you exercise in cold, the idea is that the cold creates the best workout environment for your fitness experience and optimizes the total fitness experience.

How so?

The beginning of the workout, while the body is warming up to the cold, you are probably burning calories via shivering, non-shivering thermogenesis (see below), performing the dance of joy to stay warm or by none of the above because you are a polar bear.

Once the body is warmed up through exercise, the metabolism is no longer working hard in the capacity of keeping you at 98.6°F. The mechanical heat given off by your moving muscles have done that. Your body can now focus on the task at hand: exercising and recruiting muscles to make you move. Did we say Brrrpee? Because the environment, however, is cool, instead of ambient or hot, your workout experience is better, and more efficient.

During exercise in ambient or hotter environments, competing metabolic (aka exercise) and thermoregulatory demands (aka sweating to stay cool) make it difficult to maintain an adequate cardiac output–aka, heat stress may reduce a person’s ability to achieve maximal metabolic rates during exercise.

Dropping the temperature provides a better workout experience. And a better workout experience probably means you are burning more calories.

Be sure to check out these sections below:
The Respiratory Quotient,
The Hot & Sweaty Myth,
Heat Production & Exercise

To learn more about burning calories in cold, explore these studies:

Cold exposure – an approach to increasing energy expenditure in humans

Thermogenesis challenges the adipostat hypothesis for body-weight control.

Environmental Conditioning

This is a term that has grown in popularity because of the success of journalist, anthropologist (and overall cool dude), Scott Carney and his book, “What Doesn’t Kill Us.”

Carney dubs environmental conditioning as the third pillar of fitness, behind diet and exercise.

In his book, Carney argues that focusing on diet and exercise is not enough and that cooler environments can exercise our physiologies in ways that exercise just can’t. He researched and participated in all sorts of methods that use environmental conditioning.

Perhaps most noteworthy of all, Carney wrote about Dutch guru and international cold sensation, wellness influencer and overall bad ass Wim Hof. For the record, we love Wim Hof.

Carney attempted to debunk Hof but realized that “The Wim Hof Method” is indeed legit, science-based, and can help people live better and healthier lives.

To learn more about this, here’s a great article by author Scott Carney himself:

A new theory promises to unlock your body’s full potential—and is actually scientifically sound


Have you ever noticed how you have that one friend who just doesn’t get cold that easily? It’s perhaps because they probably have more BAT fat than you do.

Let us explain.

Unlike our constitutional rights, not all fat is created equal.
There are two distinct types of fat: white adipose tissue and brown adipose tissue. White adipose tissue (WAT) is what we commonly think of as fat. It’s the stubborn type of fat that you wish away at the beginning of every New Year. It’s the type of fat that rarely appears around the midsections of all of those Instagram fitness influencers that you idolize way too much.

Brown adipose tissue (BAT), however, is actually a type of fat that you should want more of.

It’s the darker tissue found predominately on the neck, heart, shoulders and spinal cord that is activated in cold to help you stay warm. In 2009 in the New England Journal of Medicine, researchers discovered that BAT is present in the bodies of adults (they thought only babies had it).

So why brown?

That’s a great question! The reason brown fat is brown is because it’s loaded with these iron-rich organelles known as mitochondria (the powerhouse of the cell), which under a microscope look brown. When cold, BAT bypasses burning predominately glucose to make ATP and instead burns your own white fat to make heat. So in a way, it’s fat that’s burning fat to help you stay warm. And cold exposure makes this phenomenon happen! Pretty cool, right?

Here’s some more good reads:

Identification and Importance of Brown Adipose Tissue in Adult Humans

Cold acclimation recruits human brown fat and increases nonshivering thermogenesis

Could increased time spent in a thermal comfort zone contribute to population increases in obesity?

Non-Shivering Thermogenesis (NST)

If you’re cold but not shivering, your body is creating its own inner heat by burning fat through a process called non-shivering thermogenesis.

So how does your body create its own inner heat? Well you already know that because you took the time to read about BAT FAT a few tabs before this one!

To learn more, explore this article:

Identification and Importance of Brown Adipose Tissue in Adult Humans

Cold acclimation recruits human brown fat and increases nonshivering thermogenesis

Could increased time spent in a thermal comfort zone contribute to population increases in obesity?

Shivering Thermogenesis (ST)

This is a fancy, scientific way of saying… (Insert drum roll)… Shivering.

When exposed to cooler temperatures, your muscles involuntarily spasm. And this vibration creates mechanical heat to ensure your core temperature stays at 98.6°F.

Remember, your body will do whatever it takes to stay warm, even if it means shivering to the point where you look like someone just zapped you with a Taser.

Shivering just so happens to burn primarily glucose, not fat. And glucose is also the fuel source for aerobic activity.

So in a way, shivering is the first form of exercise. Did you just get goosebumps? Because we did.

Cold exposure – an approach to increasing energy expenditure in humans

Human studies concerning thermal-induced shivering, postoperative “shivering,” and cold-induced vasodilation.


Trust us, we didn’t spell the capital of China wrong.

Beiging is a phenomenon that happens your white fat cells start to take on the characteristics of Brown Adipose Tissue, aka. BAT fat., but haven’t completely converted into being fully brown. Thus, beige.

Routine cold exposure has been shown in studies to make this transformation happen.

How does it work? When exposed to routine cold, your white fat cells may start to increase in mitochondria density, thereby taking on the traits of brown adipose tissue. The whole reason cells are called brown is because under a microscope, the more mitochondria a cell has, the darker the cell looks because mitochondria are iron-rich organelles and the iron is what looks brown.

So, when white fat starts to convert into a brown cell, but hasn’t fully transformed, researchers say it looks “beige.” Most important, the cell has started to take what scientists call the “thermogene characteristic” – which means the cell is burning fat for heat.

How you benefit is you are converting fat cells in your body into fat burning cells and making you a more efficient system.


Here’s a few good reads about it:

Identification and Importance of Brown Adipose Tissue in Adult Humans

Beiging of white adipose tissue as a therapeutic strategy for weight loss in humans

The significance of beige and brown fat in humans


“Thermo” means heat. “Genesis” means creation of. Therefore, thermogenesis – simply put – is the process of heat production in the body in order to stay at 98.6°F.

We as humans are hot and bothered heatmakers – especially in New York City.

Michael Phelps

Remember during the 2008 Olympics when they were talking about how swimmer Michael Phelps ate some insane about of calories each day?

It was estimated to be 12,000-15,000 calories a day of food.

Well, it’s true.

But…not even Michael Phelps can out-exercise that. He’d have to be doing the butterfly all-day-long, every day of the week. For comparison sake, to run a marathon, you typically only burn about 100 calories a mile, so about 2,600 calories. And then you’re gassed.

Reality check: Exercise doesn’t burn that many calories. And the calories it does burn is mostly glucose, but that’s another story for another day…

So how did Phelps burn off all that food? Light bulb. He was in a pool of water most of the day, cooled to the high 70’s. Water is 24x more thermo-conductive than air, so this means that Phelps was losing his own body heat to the cool water. Remember, cool doesn’t go into the body, heat goes out. The cool water was pulling heat out of his body.

To compensate for losing that much heat, Phelp’s metabolism had to compensate. Boom. And the only way to compensate for a super-charged metabolism is by increasing caloric load—aka eating a s#*$& ton of food.

Ray Cronise, the father of the cold movement (to us), happened to be on his couch, 80lbs overweight, when the Phelps calorie story was broadcast to the American public. The rest is history. (Read about Ray below).

Ray Cronise

To us, Ray Cronise is the Father of the cold movement.

A former NASA Scientist, who happened to be some 80lbs overweight, Ray was sitting on his couch one afternoon in 2008, so the story goes, watching a feature about Michael Phelps and Phelp’s calorie consumption (read about Michael Phelps Above).

The math didn’t add up for Cronise.

There was no way Phelps was out-swimming the 12,000-15,000 calories worth of the food he was consuming every day. Then Ray figured it out. As a 15-year NASA veteran working with NASA’s Marshall Space Flight Center working on Physical and Analytical Chemistry and Biophysics as Assistant Mission Scientist on four Spacelab missions, the light bulb went on:

Phelps was in a pool of water most of the day, cooled to the high 70’s. Water is 24x more thermo-conductive than air, so this means that Phelps was losing his own body heat to the cool water. Remember: cool doesn’t go into the body, heat goes out. The cool water was pulling heat out of Phelp’s body.

This lesson in mind, Ray started infusing mild cold stress into his life—cold showers, shiver walks in his Alabama back woods, sleeping in 50°F bedroom—and he would go on to lose the weight. Transformation through cold (but remember diet plays a very important role).

His Ted Talk helped to start the conversation about the benefits of mild-cold stress. And a couple of years later, Ray was featured in Tim Ferris’s Book, The 4-Hour Body and became an internationally acclaimed authority on the topic.

To date, Cronise has co-authored two papers about the effects of mild cold stress (and caloric restriction) and recently co-authored “Plant-Based Nutrition, 2E (Idiot’s Guides).”

Ray has applied his talents in a number of capacities ranging from academic research and development to creative sales and marketing, to hosting us to geek out on all things cold.

Currently, Cronise is tackling the nutritional aspect to weight-loss via his company JustSides. We suggest you visit it at:

The two key papers Ray has co-authored:

The “Metabolic Winter” Hypothesis: A Cause of the Current Epidemics of Obesity and Cardiometabolic Disease

Oxidative Priority, Meal Frequency, and the Energy Economy of Food and Activity: Implications for Longevity, Obesity, and Cardiometabolic Disease

Heat as Dessert

As it pertains to the fitness industry, we argue that heat should be served to us as dessert – not the main course.

At Brrrn, heat is a reward after an appetizing workout served to you in the form of overhead infrared heating lights.

And this amazing treat helps us channel our parasympathetic nervous system, the “rest and digest” part of our autonomous nervous system that helps us chill out after a cool workout.

If you think about it, we live in a constant state of comfort. We wake up in warm apartments, we travel to work in heated vessels (subway, car), we work in heated offices, and we workout in ambient or heated classes, only to come home after a long day to a cozy home where we probably enjoy a hot meal and shower before we obsessively stare at hot bodies on Instagram before we go to bed.

Then we wake up the next day, and we rinse and repeat the same, hot cycle all over again.

But while this has made life easier in modern times, have our bodies caught up to such a constant access to heat and a continuously comfortable climate?

Researchers are suggesting that chronic heat is affecting our metabolism and may be a key reason we are overweight and obese as a society.

So consider this: Being spoiled with a constant heat source is preventing our body’s ability to create its own heat. It’s a lot like how spell check has made us terrible at spelling words on our own.

We are burning less of our own calories and exercising less of our natural and internal physiologies that we’ve exercised for the past millennia.

In a way, many physiologies in our bodies are going dormant. Is this really good for us?

Bottomline, at Brrrn, we will keep dessert were it belongs: after the meal.

The Sewing Needle

Did you know the sewing needle was invented only 50,000 years ago? How does this translate into you and your experience at Brrrn? It means that fashion and wearing clothing to keep us warm instead of relying on our own metabolisms is a really recent phenomenon for us Homo Sapiens.

Today, we depend too much on our fashion—aka, our self-made, layered micro-climates—to keep us warm instead of our own metabolism.

Consider that we’ve been in these Homo Sapien bodies for about 150,000 to 200,000 years and our current bodies have more in common with the lifestyle of the cave person from millennia ago than they do with the office worker sitting under fluorescent lights all day. Academics and authors like Scott Carney have drawn much attention to this concept, and we couldn’t agree more.

Break with fashion. Wear less layers. Layer down.

And most important, the wick-wear clothing you are sporting is a super recent invention!

A great read about the oldest sewing needle (that we know of):


We, as humans, are warm blooded creatures. We make our own heat instead of getting it from our environment. This makes us endothermic homeotherms.

Sexy, we know.

We make this heat through our metabolism which is the product of our trillions of cells working in concert to maintain homeostasis (aka. to stay at a constant 98.6°F). Heat production calls for more than half of the calories we burn – if not more – and is part of our basal metabolic rate.

Holy buckets, that’s a lot of calories to keep us heated. So how the heck do we fuel this constant metabolic furnace?

We eat!

Tutti a tavola! Everyone to the table!

“Giovanni, I a cooked la pasta with Uncle Angelo tonight! Open la bottiglia di vino per favore and close la window, it a cold in a here.” – Every Italian Grandmother


Did you ever watch the show Nature on PBS as a kid growing up that aired Sunday nights at 8pm CST right before Mr. Bean?

No? Ok then…

Then have you ever heard the English narrator, David Attenborough, talk about how certain snakes only eat one meal a year?

No again? Alright, well, just pretend that you have.

The reason why snakes only eat once a year is because they are ectothermic and don’t need to consume a lot of calories because they don’t produce their own body heat. Snakes get their heat from their environments, which is a key feature amongst ectotherms: such as turtles, reptiles and probably the sea creature in Guillermo del Toro’s 2018 Oscar winning film, “The Shape of Water”.

Ectotherms rely on their own behavior to regulate their body temperature, meaning they must move their bodies into the shade or sun to cool down or warm up. Seeking outside heat source requires less energy than fueling a constant metabolic furnace. And if you have an appetite for snake jokes, then feast your eyes on the joke below:

Q: What do you call a funny snake?

A: Hissterical!

You’re welcome.

Hot Weather Makes Us Unhappy

This 2016 paper, which we first learned about in this 2017 Washington Post story, analyzed and logged markers/expressions of
sentiment and mood across 1 billion tweets. Case in point, the study suggests there is indeed a correlation between temperature and temperament.

When are people in the best of moods…aka the happiest?

Answer: 55°F.

Very cool indeed.

How Bears Stay Cool in Summer (aka, Unbearably Hot)

Because bears are big furry creatures, they sure do get hot come summer. So how do they stay cool?

Bears in summer happen to dump heat through their paws, noses and feet. Known as glabrous skin, this hairless skin serves as a vehicle through which Bears can dump all that internal heat produced by bears and trapped in by their fat and fur.

Fun fact: Scientists think humans dump heat the same way. Look at the palms of your hands, the tips of your nose and your ears. Hairless, Yes? If not, all good. We accept you for who you are.

In fact, it gets cooler. All this cool science was recently discovered by Stanford biologists. They found out that humans and bears both share a special highway of arteries and veins in our arms and hands, known as AVAs (arteriovenous anastomoses), that bypass the capillaries to regulate our internal temperature directly out of our palms when we get hot.

According to these Stanford biologists H. Craig Heller and Dennis Grahn, “these networks of veins, seem exclusively devoted to rapid temperature management. They don’t supply nutrition to the skin, and they have highly variable blood flow, ranging from negligible in cold weather to as much as 60 percent of total cardiac output during hot weather or exercise.”

To learn more about their discovery, check out this article below:

Stanford researchers’ cooling glove ‘better than steroids’ – and helps solve physiological mystery, too

How Bears Stay Warm in Hibernation (aka, Unbearably Sleepy)

Does a bear eat when it hibernates in winter? No. It uses its own fat as fuel.

So what’s the thesis here with bears?

Answer: To not sleep on winter.

(FYI: That’s Brrrn slang for us saying to not ignore winter but rather to welcome it in your life).

We’ve been evolving for thousands of years where an annual period of cold makes food and heat scarce. We, in modern times, just happen to continue living through winter (pretty active lives actually) whereas bears take a giant nap and accept the seasonality of cold.

Case in point: Be like a bear and embrace winter. Chill for a bit, relax, and “hygge-out” with some extra blankets to a bingeworthy Netflix show.

Respiratory Quotient

Ever been at a gym and it says you are in a high calorie burning zone? Well, while this is arguably true, we argue at Brrrn that it’s the type of calorie that matters.

Are you are burning glucose or fat?

Pretty much at any given moment, you are always burning a combination of the two to keep you alive, unless you are performing explosive movements. Oh yeah, quick science fact here, our bodies predominately use either glucose (and glycogen) when we are cranking out burpees as fast as can be.

We know this because of our respiratory quotient.

The respiratory quotient (RQ) is essentially a ratio of carbon dioxide eliminated to oxygen consumed, and what’s crazy is this in turn tells us the ratio of glucose to fat our body is burning.

How do you capture it? Well, you have to wear a mask like Darth Vader where you can capture oxygen in and Co2 out. Simple as that.

The ratio of glucose to fat changes constantly: when we bicycle to the gym, when we sleep, when we sit at a work desk for a few hours, when we start to exercise really hard, and even when we are exposed to cooler air or water, our bodies shift to burning different ratios of glucose to fat.

Most interesting to our discussion about exercise and cold is this: When you exercise really hard (again, think explosive movements like a burpee) your RQ is close to 1.0, if not over. This means you are burning 100% glucose to fuel your exercise. You might be burning what seems like a lot of calories (according to your calorie counting gadget that is), but we reiterate here, these calories are glucose, not fat. And this is what we mean by the type of calorie you are burning. It’s something only not even your calorie counting gadget can inform you about.

On the contrary, mild cold stress dress drops the RQ significantly. In studies, when exposed to cold, and this occurs after shivering ceases or if the shivering never begins (remember, shivering is a form of exercise whereby your muscles are vibrating very much like exercise which raises the RQ), the RQ falls near the .7 marker. For example, if you jumped into a cold lake, your RQ may fall to .75 or even lower, and this would mean you are burning predominately fat in the cold. Crazy!

(Former Nasa Scientist and the Father of Cold, aka, Ray Cronise (read above) taps into the RQ in his paper Oxidative Priority. Ray and his co-authors suggest that simply sitting at your desk, your RQ is probably around .85, which means your metabolism is burning 50% fat and 50% glucose.

In short, whereas exercise uses mostly glucose (and glycogen) as its fuel source, exposure to a cool environment uses more fat as its fuel source, and the reason we know this is because of the respiratory quotient and the fact we pulled way too many all-nighters and drank a ton of coffee learning all this stuff.

To learn more, click this:

An overview of the respiratory quotient

Metabolic Winter Hypothesis

The unintended consequence of modernization—specifically, the securing of a food and a centralized heating system—has left us, chronically fed and chronically warm in affluent society. Winter never comes anymore. Thank you Ray Cronise for teaching us this.

This is indeed the theory posited in the article “The Metabolic Winter Theory: A Cause of the Current Epidemics of Obesity and Cardiometabolic Disease,” in the journal “Metabolic Syndrome and Related Disorders” in 2014, co-authored by Ray Cronise and his fellow authors; Dr. David Sinclair, a Professor in the Department of Genetics at Harvard Medical School and co-Director of the Paul F. Glenn Center for the Biological Mechanisms of Aging; and Dr. Andrew Bremer, the Program Director for the Division of Diabetes, Endocrinology, and Metabolic Diseases for the National Institute of Health for Diabetes, Digestive and Kidney Diseases.

According to their theory, we currently live in one seasons: summer. Aka, we pretty much live in a warm, bright, active and abundant environment all the time. We’re never in winter anymore, which is defined by cool, still, dark and scarce.

To their point, our 7-million-year evolutionary path was defined by two seasonable challenges: food scarcity and cold…aka winter. Yet, in the past half-century, we’ve solved them both. We’re never hungry or cold anymore in affluent society.

To their point, winter never comes anymore.

Gives you something to think about, right?

You can access the article here:

The “Metabolic Winter” Hypothesis: A Cause of the Current Epidemics of Obesity and Cardiometabolic Disease

It’s Always 72°F & Sunny

Today, many of us are shielded almost continually, by year-round, 70-something-degree comfortable environments. When temperatures turn colder, most of us quickly put on a sweater or turn up the thermostat.
In deep winter, we run from the house to the car and crank up the heat—always staying indoors. Technological advancements in heating efficiency, and even fashion, have allowed us to avoid cold exposure almost always in the twenty-first century.

And this constant warmth, according to scientists, is slowly changing our physiologies.

Specifically, bad-ass academics like Dutch Researcher Dr. Wouter D. van Marken Lichtenbelt, Ph.D., at Maastricht University in The Netherlands in the Department of Ecologic Energetics & Health has lead a host of research exploring this cool topic. Linchtenbelt argues that year-round warmth is a modern luxury and is changing the human metabolism. He argues regular exposure to mild cold temperatures may provide a healthy and sustainable alternative strategy for increasing energy expenditure in humans.

To learn more, explore his papers:

Collection of Cold Stress Papers by Dutch Researcher Dr. Wouter D. Van Marken Lichtenbelt, Ph.D., at Maastricht University in The Netherlands in the Department of Ecologic Energetics and Health

Cool, Dark, Still & Scarce

This is Ray Cronise phraseology for what winter is really about. We shouldn’t fight it but accept winter for what it is, a season when food is scarce and heat is lacking. Perhaps instead of fighting it with heat and light, we should accept winter for what it is.

To read more about this, explore Ray’s paper:

The “Metabolic Winter” Hypothesis: A Cause of the Current Epidemics of Obesity and Cardiometabolic Disease


Irisin is a chemical hormone messenger produced in our muscles.

It was recently discovered by cell biologist Bruce Spiegelman and colleagues at the Dana-Farber Cancer Institute at Harvard Medical School in 2012 and reported on in the Journal Nature.

Through shivering and exercise, the body secretes irisin into the blood circulation to talk to various tissues in the body, hence its name, in reference to the Greek mythological goddess Iris, messenger of the gods.

We like Bruce a lot for this cool name!

One of the cool things about Irisin scientists are seeing is that it induces energy-storing white fat cells to take on characteristics of brown fat. Pretty cool!

Science is indeed cool.

To read more about recent discovery of Irisin in 2012, here are some papers:

A PGC1-α-dependent myokine that drives brown-fat-like development of white fat and thermogenesis.

Irisin and FGF21 are cold-induced endocrine activators of brown fat function in humans

About Irisin in the journal Nature:

A PGC1-α-dependent myokine that drives brown-fat-like development of white fat and thermogenesis

Newton’s Law of Cooling

Cool doesn’t go into the body. Heat goes out. The cooler the temperature of the environment, the faster our 98.6°F bodies lose heat. This is, in essence, known as Newton’s Law of Cooling.

The theory is named after English physicist Sir Isaac Newton (remember that apple falling on his head?) who in the late 17th century, conducted the first experiments on the nature of cooling. He experimented with what we know now is the field of thermodynamics, but that’s a whole other conversation…like NASA rocket science conversations.

Here’s a fun fact: Water is 24x more thermoconductive than air. This means you lose your own body heat 24x faster in water than in air.

(In a bad Matt Damon impression from Good Will Hunting)
So how about dem apples?


More about Newton’s Law of Cooling


This is our signature breathing technique performed at the end of each class. What we found through our own experiences is that mindfulness begins with breath.

How Comfort Kills

We believe that modern comforts are killing us slowly—specifically, our consumption of heat and food. So in our opinion, if you want to live a better (and hopefully longer) life, start adopting a more nutrient dense, calorie deficient eating lifestyle (see Ray Cronise’s section) and warm up to the idea of frequently embracing cooler temperatures.

Are You Reading This At Work?

Just curious.

Securing a Central Heating System

If you’ve only heard it once, then let this be the next time you heard it: We are celebrating the s#*% out of heat in these modern times –and rightfully so.

As humans we’ve been cold for millennia and securing a heat source in the past wasn’t as easy as it was today (aka, aka, hitting a button on a thermostat). Without an organized society to supply and support this centralized heating system, cold was very much a daily stressor on life. No wonder we flock to a heat source every chance we get.

We think we’re subconsciously drawn to heat in a way because it means our metabolism gets a break from burning our own supply of fat, fat we’ve worked very hard to store-up in case a famine or a period without heat falls upon us.

Tip of the hat to you, Ms. Radiator.

Tummo Meditation

Tummo, also referred to as g-tummo, is a form of meditation that involves forceful breath to heat the body. It is a sacred practice of the Indo-Tibetan traditions of Vajrayana Buddhism and Bon.

Also known as vase breathing or physic heat, a notable study, published in 1982 in Nature, involved measuring the internal temperature on a group of nuns in the sub-freezing temperatures of the Himalayas. According to the study, the nuns were able to increase their core body temperature with this technique — up to almost 101 degrees Fahrenheit.

Called vase breathing, another study was recently done on 11 Westerners in New Jersey (out of all places!) to see if the same effects could occur. The study found that reliable core body temperature increases were observed in this group, and that non-expert meditators can do this ancient breathing practice.

What is the core of the G-Tummo Breathing?
During the inhale of the practice, participants should contract their abdominal and pelvic muscles, thereby expanding the lower belly, to take the shape of a vase or pot. Interestingly enough, in both of these studies, researchers found that the meditative forced breath component can also increase a core temperature

The visualization component involves imagining flames near the spine, for the sustained heat increase.

At Brrrn, our breathing practice is called Brrreath™, which is g-Tummo inspired breath meditations that focus on mindful inspiration and expiration as a means to heat the body in our cooler workout environment. (Insert breathing room joke).

To learn more, explore these studies:

Neurocognitive and Somatic Components of Temperature Increases during g-Tummo Meditation: Legend and Reality

Body temperature changes during the practice of g Tum-mo yoga

The Hot & Sweaty Myth

Sweating is the body’s natural cooling process. When you exercise in ambient or hot temperatures (72°F or warmer), you lose water weight through sweat. This doesn’t mean the workout is any better, as research is suggesting that the higher the temperature the worse your performance. . .

Our internal central organs—specifically the liver, kidneys, and intestines—rise above 101°F during exercise. When this happens, water and blood begin to leave the muscles and race to the skin in an attempt to cool the body. The body is literally dumping heat. This may deplete the muscles of oxygen and dehydrates them, causing fatigue and impacting performance.

Conversely, cooler temperature conditions regulate internal temperature, presenting an advantage for cardio and resistance training.

Exercise and heat dissipation (sweating) make competing demands on the cardiovascular system, in particular, in both ambient and hotter environments.

It’s like trying to talk to your mom on the phone while having an in-person conversation with your best friend. Both are lacking your full, undivided attention. Exercise in a hot environment, in our opinion, is no different.

Read more below in Heat Production & Exercise to learn more.

Heat Production & Exercise

The body produces a ton of heat during exercise. In fact, the US Army’s division of Environmental Sciences in Natick, MA recognize a significant deficit in physical performance of military personal when faced with ambient and hot (hyperthermic) environments versus cooler and cold environments (hypothermic). Vigorous exercise can increase heat production significantly within the body, raising the core temperature to dangerous levels (103°F and higher).

During exercise, competing metabolic (aka exercise) and thermoregulatory demands (aka sweating to stay cool) make it difficult to maintain an adequate cardiac output–aka, heat stress may reduce a person’s ability to achieve maximal metabolic rates during exercise.

Dropping the temperature provides a better workout experience.

Here are a few key studies about it:

Impact of weather on marathon-running performance

Physiological Responses to Exercise in the Heat

Effects of ambient temperature on the capacity to perform prolonged cycle exercise in man.

Methods, advantages, and limitations of body cooling for exercise performance

Effects of heat removal through the hand on metabolism and performance during cycling exercise in the heat.

Heat extraction through the palm of one hand improves aerobic exercise endurance in a hot environment.


This is a term defined in the biology and medical communities, but has also made its way into certain pubs after a few pints and some hits from your cool cousin with the “eco-friendly” vape pen.

But enough about what Jimmy and Johnny do on the weekends…

Hormesis is defined as an adaptive response of cells and organisms to a moderate (usually intermittent) stressor. Cold is certainly one of these natural stressors, as is exercise.

So what happens when the body is exposed to this stress?

It responds.
It fights back.
It grows stronger and adapts.

Amazing things can happen if you can summon the courage to step outside your comfort zone.

To learn more, explore this study:

Hormesis Defined

The Pull a Muscle Theory

We have gotten this question a lot when we were fundraising for Brrrn.

If you think about it, your body is already warm. Your core’s at a pretty constant state of 98.6°F pumping that warm blood throughout you. You are also chock full of layers, like, you gots lots of layers, keeping your body heat in. We’re not kidding, from top, starting with clothing, to bottom:

Clothing, Hair, Skin, Fat, Three layers of Fascia, Muscles

Under this skin and within all this is your vasculature of flowing blood. Did we mention layers of clothing? Your muscles are doing just fine. We think you’ve been fed this myth that temperature is the culprit. It’s not.

So how do you pull that muscle?

Your risk factor of pulling a muscle is increased and influenced by your movement patterns outside of your fitness experience. For example, if you are an office worker, you are probably sedentary most of the day and could develop certain over active and underactive muscle systems— like tight quads or weak glutes. A forward lunge at Brrrn that results in a pulled leg muscle is more an unintended consequence of that sedentary lifestyle than the 45-minutes in our cooler environment. Catch our drift?

So rest assured, the only time that we’re pulling your leg is with our sense of humor – not our workout temperatures.

But let’s not stop here. Muscle recruitment involves a host chemical, bio-mechanical and even neuro recruitment activations within the body. Aka, there’s a lot going on here and it certainly parlays into our ankle, knee, hip, shoulder, elbow and wrist joints.

Where are we going with this?

Our joints should be lubricated before we move. Whether we exercise in hot, ambient or cold temperatures, the body doesn’t want to be like the Tin (wo)man when starting to do those brrrpees. It wants to be super greased up!

But in order to have lubricated joints, the body needs bio-mechanical and chemical ignitions to transfer what’s called synovial fluid, literally a polymer-like fluid our bodies make naturally, that live outside of the joint capsule, to be sent into your ankle, knee, hip, shoulder, elbow and wrist joints.

And this is why we are putting you through a Pre-Heat movement series at Brrrn.

So, in short, don’t blame the temp if you pull a muscle. Instead, reflect on the above!

Hypothermia versus Hyperthermia

Hypothermic Environment: We define a hypothermic, aka, a cold environment, as anything colder than co-Founder Johnny’s parents’ garage, where they stored the beer growing up in Wisconsin in the ‘80s and ‘90s. So, like 35°F or colder.

Hyperthermic Environment: We define a hyperthermic, aka, a hot environment, as anything warmer than Boca Raton, Florida where our amazing web designer, Jenni, of Solmark Creative, lives with her husband Mike and kids. If you’re looking for a web designer, Solmark has got you covered.


This is the name of a tattoo that our co-founder, Johnny Adamic, wants to get after we reach our 1000th Brrrn customer.

But personal goals aside, PGC-1a is a gene, which studies show is expressed through cold exposure. Studies also show that this gene is associated with an increase in mitochondria density in the muscles – which revs up metabolism. If you want to dork out for a minute, this is known in the scientific community as “mitochondria biogenesis-related gene expression.” It is also the vocal warm up that Jimmy uses before every public speaking appearance.

To learn more, explore these articles:

The “Metabolic Winter” Hypothesis: A Cause of the Current Epidemics of Obesity and Cardiometabolic Disease

The effects of exercise and cold exposure on mitochondrial biogenesis in skeletal muscle and white adipose tissue

The Cold Finish

We finish every shower we take on cold at Brrrn and at home. Consider that cold baths and showers have an extended history in numerous cultures, and for good reason: Cold water bathing has achieved broad success as a therapy for a number of ailments across the centuries.

Cold water treatments, however, have fallen out of vogue in the latter part of this century as medical professionals have begun to depend more on other forms of practices (aka., science-based, duh) to treat illnesses. As a result, the hot shower has now become de rigeur.

We’ve completely forgotten about the power of cold. And it sure is powerful.

It’s time to bring the cold shower back.

There’s a ton of stuff out there about the benefits of cold water exposure so…

Finish Cold.

Here are few of the benefits and we encourage you to read and interpret these with the same dosage of skepticism as we have:

Cold showers may help in the production of healthier hair.
Cold showers may boost mood.
Cold showers may deepen breathing.
Cold showers may improve lymphatic movement.
Cold showers may regulate temperature.
Cold showers may improve blood circulation.
Cold showers may strengthen immunity.
Cold showers may boost recovery after exercise.
Cold showers may decrease inflammation.
Cold showers may result in better sleep.
Cold showers may help the body become stronger and adapt to stressors.

Further reading about cold showers:

The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial

Adapted cold shower as a potential treatment for depression

Winter swimming improves general well-being

Effects of long-term whole-body cold exposures on plasma concentrations of ACTH, beta-endorphin, cortisol, catecholamines and cytokines in healthy females

Howie Day

Co-Founder Johnny Adamic is obsessed with Howie. We’re serious. He has, like, so many of his set lists.

And from what Johnny says, Howie loves science and nature and is one cool dude. Like duh, Howie is from Maine, and Maine is one cool state.

So if Howie’s reading this, please know that Johnny has given you an invitation to come to Brrrn as often as you’d like. But don’t be surprised if Johnny asks for you to play an acoustic set one day in Brrrn’s rustic, hygge lobby.

He thinks it would literally be the coolest set ever. #stopalltheworldnow

Check out more about Howie Day by by going to

Cold Acclimation

Frequent exposure to cold air results in cold acclimation whereby the human body recruits brown fat and increases non-shivering thermogenesis. Cold no longer feels cold but normal. Pretty cool, hey!

So if you’re looking to beat Father Winter himself, then beat him at his own game by playing it more often.

One reason for acclimation has to do with the amount of BAT and Beige fat you have which you can read above!

Here are a few key studies about it:

Cold acclimation recruits human brown fat and increases nonshivering thermogenesis

Differences between young adults and elderly in thermal comfort, productivity, and thermal physiology in response to a moderate temperature drift and a steady-state condition.

Beiging of white adipose tissue as a therapeutic strategy for weight loss in humans

The significance of beige and brown fat in humans


Cryotherapy is a form of cold exposure where you stand in a chamber of air chilled to about -250°F for three minutes. Ever walked down Michigan Ave in Chicago on a January night?

At Brrrn, we are a less concentrated form of cold exposure where you exercise in temperatures that range from 45-60°F as a means to improve the fitness experience.

So think of Brrrn as a cup a coffee and Cryo as a triple shot of espresso.

Get in a Cryo session today at Cryofuel, owned by our friends Ben and Simon!

To learn more, watch our Cool Facts Friday episode here about Cryo!

Eat The Same, Lose Weight

Exposing our bodies to temperatures as warm as 60°F (we think this is warm) requires a rev in our metabolism. Research is suggesting that the metabolic increase through cold exposure is enough such that a dietary intervention is not needed.

This means you don’t have to change your diet if you bring more cold into your life.

When our bodies are exposed to temperatures between 40-64°F, studies show we activate a host of physiologies—processes that not even exercise can channel—to ensure our core stays nice and toasty.

Our body seeks to operate at homeostasis (98.6°F). So we either do it ourselves through our own metabolism or we rely on something else to do it for us (i.e. clothing, central heating or heated conversation with those you love).

To summarize: When you’re exposed to temperatures as warm as 64°F, and if you are wearing a short-sleeve shirt and shorts, and depending on your percentage of body fat and other factors (e.g., age, sex, satiation levels, etc.), your metabolism will start to increase, burning a combination of glucose and fat as fuel to ensure your core body temperature stays at 98.6°F. This causes a weight loss and burns so many calories that you may not even have to change your diet.

To learn more, explore this paper:

Thermogenesis challenges the adipostat hypothesis for body-weight control.

Rich Roll

Co-Founders of Brrrn, Johnny and Jimmy, listened to a heck-of-a-lot-of the Rich Roll Podcast while making Brrrn a reality. Both Johnny and Jimmy hope to meet Rich and share their story on his podcast one day without making things super weird.

Needless to say, we encourage you to listen to his podcast. He is truly a “Roll” model, that’s for sure!

Check out his webiste here:

Vasoconstriction & Vasodilation

This is the term for your blood flow when exposed to cold temperatures or warm temperatures. When cold, your blood vasoconstricts to your core, to keep you organs at 98.6°. Your hands, fingers, feet and toes are all ancillary to keeping you alive.

Once you return to warmer temperatures or stay warm yourself by moving, shivering, or by activating your BAT fat, you may start to vasodilate, which will draw your blood flow back to your arms and legs. #coldfeet