使用主动冷暴露改善健康与表现

安德鲁·休伯曼：

Welcome to the Huberman Lab 播客, where 我们 discuss science 和 science-based tools 对于 everyday life.

安德鲁·休伯曼：

I'm Andrew Huberman 和 I'm a professor of 神经生物学 和 ophthalmology at Stanford School of Medicine. Today 我们 are going to discuss the use of 主动冷暴露 对于 健康与表现. 温度 is a powerful stimulus on 我们的 神经系统 和, indeed, on every organ 和 系统 of 我们的 身体. 和 寒冷 in particular 可以 be leveraged to 改善 心理健康, physical 健康与表现, meaning 对于 耐力 运动, 对于 recovering 从 various forms of 运动, 对于 actually improving 力量 和 power, 和 对于 增强 mental capacity.

安德鲁·休伯曼：

In order to properly leverage 主动冷暴露 对于 sake of 心理健康, physical 健康与表现, 你 have to understand how 寒冷 impacts the 大脑和身体. So today 我们 are going to discuss 那. 我们're going to talk 关于 some of the neural 回路 和 通路, some of the 激素 involved. I promise to make it all clear 和 accessible, regardless of whether 或 not 你 have a scientific background 或 not.

安德鲁·休伯曼：

我们 are also going to discuss 非常 具体的 方案 那 你 可以 apply which leverage variables like 温度: how 寒冷, how to deliver the 寒冷 — 对于 instance, whether 或 not use a 冷水淋浴, 寒冷 immersion, ice bath, circulating 水, 或 still 水, whether 或 not 你're going 对于 walks outside in a T-shirt when it's 寒冷, 或 whether 或 not 你're purposefully using things like cryo if 你 have access to 那 或 not.

安德鲁·休伯曼：

一 thing I 可以 promise 你 is 那 by the end of today's episode, 你 会 know a lot 关于 the biology of thermoregulation. 那 is how 你的 大脑和身体 regulates its 温度. 你 会 also have a lot of tools in 你的 arsenal 那 你 可以 use 和 leverage toward improving 心理健康, 身体健康, 减少 炎症 in the 身体, improving athletic 表现, improving 心理表现. I promise to spell out all 那些 方案 in detail as I go along 和 to summarize them again at the end.

安德鲁·休伯曼：

I'd like to make a point now 那 I'm going to make several additional times 期间 today's episode, 和 那 is 那 温度 is a 非常 potent stimulus 对于 the 大脑和身体. 那 also means 那 it carries certain hazards if it's not done correctly.

安德鲁·休伯曼：

Now everyone shows up to the table, meaning to 方案, 与 a 不同的 background of health status, 和 there's simply no way 那 I 可以 know what 你的 health status is. So anytime 你 are going to take on a new 方案, 那 means a behavioral 方案 或 a nutritional 方案 或 a supplementation 方案, 你 应该 absolutely consult a board-certified physician 之前 initiating 那 方案. I don't just say 这 to protect us. I also say 这 to protect 你. If 你'd like to see 我们的 medical disclaimer, 你 可以 go to 我们的 show notes. It's described there. In fact, I encourage 你 to please do 那. 和 in general, when embarking on new 方案, in particular, if they involve strong stimuli like changing 温度 或 placing yourself 进入 unusual temperatures, I 会 encourage 你 to progress gradually.

安德鲁·休伯曼：

I 会 also encourage 你 to not look at gradual progression as the kind of weak version of a 方案. In fact, today I'm going to discuss a 确实 beautiful peer-reviewed 研究 那 involved having 人们 do 主动冷暴露. So they were immersing themselves 进入 水 up to 关于 their neck, 和 the 水 was actually not 那 寒冷. It was only 关于 60 degrees Fahrenheit, which 对于 most 人们 is pretty tolerable. So nowhere near the kinds of extreme temperatures 那 一 could use in other 方案. 和 the interesting thing is, despite 那 fairly modest 寒冷 温度, by simply extending the duration of time 那 人们 were in 那 水, they experienced enormous 增加 in 神经化学物质 那 ought to translate to improvements in 专注 和 情绪. 和 indeed, 那's what's been observed in subsequent 研究. So again, please see 我们的 medical disclaimer in 我们的 show notes. Please proceed 与 caution 总是. Please also understand 那 the most potent stimulus isn't 总是 the 一 那 你 experience as the most intense in the moment.

安德鲁·休伯曼：

In fact, I 会 encourage 你 to find the minimum threshold of stimulus 那 会 allow 你 to drive the maximum benefit 从 each 方案. 和 indeed, I 会 point out what 那些 thresholds ought to be today. I'll give 你 some simple formulas, gauges, 或 guides 那 你 可以 use in order to navigate 这 extremely interesting 和 potent tool 那 我们 call 主动冷暴露.

安德鲁·休伯曼：

之前 我们 talk 关于 主动冷暴露 和 its many powerful applications, I'd like to highlight a 研究 那 I find particularly interesting 和 那 I think 你 会 find particularly interesting 和 useful. The title of 这 研究 is "Brief aerobic 运动 immediately 增强 visual attentional control 和 perceptual speed. Testing the mediating role of feelings of 能量."

安德鲁·休伯曼：

Now, the reason I like 这 研究 is 首先 of all, it's a fairly large-sized sample group. They looked at 101 students. 这些 were college-aged students. 和 they had 二 groups. 一 group did 15 分钟 of jogging at moderate intensity. So they did measure percent 心脏 rates, et cetera. 但 这 会 be analogous to zone 2 cardio, which I've discussed on 这 podcast 之前.

安德鲁·休伯曼：

Zone 2 cardio is cardiovascular 运动 那 places 你 at a 水平 where 你 可以 hold a conversation 与 a little bit of strain, meaning 那 你 可以 get the words out, 但 every once in a while 你 have to catch 你的 breath. Whereas if 你 were to push any harder, by any mechanism, going faster 或 on a steeper incline, et cetera, 那 你 会 have a hard time carrying out a conversation. So zone 2 cardio is a common form of describing 那 水平 of intensity 那 they call moderate intensity. So 一 group did 15 分钟 of jogging at moderate intensity, which I'm translating to roughly zone 2 cardio.

安德鲁·休伯曼：

The other group did 15 分钟 of relaxation concentration 那 is somewhat akin to mindfulness meditation. 和 then they were analyzed 对于 perceptual speed, visual attentional control, something called working memory, which is 你的 ability to keep certain batches of information online. Just imagine someone telling 你 their phone number 和 你 have to remember 那 sequence of numbers in 你的 head 对于 some period of time. 那's working memory, 和 it depends 非常 heavily on the so-called prefrontal cortical networks, which are involved in planning 和 action.

安德鲁·休伯曼：

和 they also looked at 人们's feelings of 能量, 和 they measured 那 subjectively, how energetic 人们 felt. Now, the major takeaways 从 the 研究 那 I'd like to emphasize are 那 the 15-分钟-of-jogging group experienced elevated 水平 of 能量 对于 some period of time 之后 they ceased the 运动, whereas the group 那 did mindfulness meditation actually reported feeling 更多 calm 和 having 更少 overall 能量.

安德鲁·休伯曼：

Now, 那's 非常 subjective, 和 indeed, they used subjective measures to analyze 能量. 但 what gets interesting is when they looked at 表现 on 这些 various cognitive tasks. 和 the 二 tasks 那 they used were called the trail-making tests. They have 不同的 versions of 这. Version A, version B. I don't want to go 进入 too much detail. 但 version A 本质上 involves having a page of numbers 那 are distributed somewhat randomly. So 一, 二, 三, four, five, six, seven, eight 和 so on, 但 distributed randomly across the page, 和 人们 have to use visual search to circle 那些 numbers in sequence. So 这 involves visual 注意力, it involves some motor skills, involves a number of things 那 certainly require 能量 和 专注.

安德鲁·休伯曼：

The 秒 test was the trail-making test. Part B, as I mentioned earlier. 和 这 involved also circling numbers in sequence, 但 interspersed between 那些 numbers were letters. So rather than just having to circle off numbers in sequence, they actually had to connect 一, then the letter A, then 二, then the letter B, et cetera. 和 remember, 这些 are randomly distributed across a page.

安德鲁·休伯曼：

The major takeaway 从 the 研究 is 那 the group 那 did the 15 分钟 of moderate 运动 prior to 这些 二 tests showed significant 降低 in the amount of time required to complete 这些 tests accurately. 那 is interesting 和, indeed, surprising, at least to me, 因为 there have been many 研究 looking at the effects of mindfulness meditation on the ability to 专注. The key variable in the 研究 turned out to be 能量, 这 feeling, subjectively measured feeling, I 应该 say, of having 更多 能量 和 thereby the ability to 专注 尤其是 in 这些 high-cognitive-demand tasks.

安德鲁·休伯曼：

Now, the takeaway 从 这 研究 对于 all of us, I think, is pretty straightforward. If 你 are going to sit down to do some work 那 requires 专注 和 working memory 和 cognitive 注意力, 和 尤其是 if it's some visual-spatial control, meaning 你 have to search 对于 things on a page, 你 have to organize things on a page. So 这 会 be writing, arithmetic, basically cognitive work of any kind. Fifteen 分钟 of moderate 运动 done prior to 那 work bout could be 非常 beneficial 对于 你.

安德鲁·休伯曼：

这 does not mean 那 mindfulness meditation 会 not be of benefit to 你. I wouldn't want 你 to conclude 那. 但 if 你 had to choose between doing 15 分钟 of mindfulness meditation 和 doing 15 分钟 of moderate 运动 prior to a cognitive work bout, I 会 say the 15 分钟 of moderate 运动 会 be 更多 valuable, at least based on the 数据 in 这 paper.

安德鲁·休伯曼：

In many previous podcasts, I've talked 关于 the powerful effects of doing things like mindfulness meditation 和 other forms of NSDR, non-sleep deep rest. So 这些 could be 20-分钟 naps 或 just lying there quietly 与 你的 eyes closed; 或 yoga nidra, 或 NSDR, scripts are available on YouTube 和 various other places, free of cost of any kind. 你 可以 just go to YouTube, put in NSDR, non-sleep deep rest. 那些 方案 have been shown to be 非常 beneficial 对于 增强 neuroplasticity. The changes in the 大脑和身体 那 encode 或 shift the neural 回路 那 allow 对于 memory to change, 那 allow 对于 learning to occur 之后 a learning bout. What I'm referring to today 和 in 这 particular 研究 is the use of moderate 运动 in order to 增加 一's 专注 和 注意力 in order to trigger 那 neuroplasticity.

安德鲁·休伯曼：

So the simple sequence here is: get energetic 和 alert, do 那 prior to the learning bout, engage in the cognitive work 或 learning bout, 和 then mindfulness meditation, NSDR, 和 so forth 应该 follow. 和 if 你 会 like to access 这 paper 和 like to look 更多 at the details in the paper, 我们'll be sure to put a link in the show notes. The 首先 author is Legrand, 和 again, the title of 这 paper is "Brief aerobic 运动 immediately 增强 visual attentional control 和 perceptual speed." Testing the mediating role of feelings of 能量. 和 I also just want to emphasize immediately, I think most 人们 out there are interested in tools 和 方案 那 work the 首先 time 和 那 work every time. 和 indeed, I think 这 方案 fits 那 bill.

安德鲁·休伯曼：

之前 I begin, I'd like to emphasize 那 这 podcast is separate 从 my teaching 和 研究 roles at Stanford. It is 然而 part of my desire 和 effort to bring zero-cost-to-consumer information 关于 science 和 science-related tools to the general public.

安德鲁·休伯曼：

In keeping 与 那 theme, I'd like to thank the sponsors of today's podcast. Okay, let's talk 关于 the use of 寒冷 对于 健康与表现. I confess, I love 这 topic 因为 it takes me back to my undergraduate years when I worked in a laboratory studying 寒冷 physiology, its effects on the 大脑 和 its effects on the 身体.

安德鲁·休伯曼：

和 over the years, I've 总是 kept track of the literature in 这 area, 和 indeed, there have been some tremendous discoveries both in animal models, so in rodents like mice 和 rats, 但 also in humans. 和 today 我们're going to talk 关于 both categories of 研究. 和 I'll be careful to point out when discoveries were made in animal models 和 when they were made in humans.

安德鲁·休伯曼：

A key point when thinking 关于 the use of 寒冷 as a tool. 和 the key point is 那 你 have a baseline 水平 of 温度 那 is varying, changing across the 24-小时 cycle. So any use of 主动冷暴露 is going to be superimposed on 那 rhythm, 那 昼夜节律, meaning 那 24-小时 rhythm.

安德鲁·休伯曼：

The basic contour of 你的 昼夜节律 in 温度 is 那 approximately 二 小时 之前 the time 你 wake up is 你的 so-called 温度 minimum. So 你的 温度 minimum is a time within the 24-小时 cycle when 你的 体温 is at its lowest. So if 你 normally wake up 大约 6:00 a.m., 你的 温度 minimum is probably 关于 4:00 a.m. If 你 normally wake up at 关于 7:00 a.m., 你的 温度 minimum is probably 关于 5:00 a.m. It's not exactly 二 小时 之前 你的 wake-up time. It's approximately 二 小时 之前 你的 wake-up time.

安德鲁·休伯曼：

Now, as 你 go 从 你的 温度 minimum to the time in which 你're going to awake, 你的 温度 is rising slightly. 和 then at the point where 你 wake up, 你的 温度 starts to go up 更多 sharply 和 会 continue to go up 进入 the early 和 sometimes even 进入 the late 下午. 和 then sometime in the late 下午 和 晚上, 你的 温度 会 start to decline. 和 indeed, as 你 approach sleep, 你的 体温 会 drop by anywhere 从 一 to 三 degrees.

安德鲁·休伯曼：

和 in fact, 那 降低 in 核心体温 is 重要, if not essential 对于 getting 进入 和 staying in deep sleep. Okay, so 温度 rises 与 waking. 那's easy to remember. It tends to continue to rise throughout the 天. 和 in the late 下午 和 晚上, 你的 温度 会 start to go down 和 the drop in 温度 actually helps 你 access sleep. 那 background 或 what 我们 call baseline 昼夜节律 in 核心体温 is 重要 to remember 因为 it helps us frame both the effects of 主动冷暴露 和 helps us frame when 你 可能 want to use 主动冷暴露 in order to access 具体的 states. It also points to times within the 24-小时 cycle when 你 可能 want to avoid using 主动冷暴露 if 你的 primary goal is to get to sleep. Okay, so 那's the 昼夜节律 in 温度.

安德鲁·休伯曼：

Now, I just briefly want to touch on thermoregulation at the 水平 of the 身体 和 the 大脑. 和 这 会 be 非常 surprising to many of 你. Let's do what's called a Gedankin experiment, which is a thought experiment. Let's say I send 你 out 进入 the desert 热 对于 a jog 或 a run, 和 it's 非常 hot outside, 102 degrees 或 103 degrees, 和 你 start to move, 你 start to 汗液, 和 of course 你的 核心体温 goes up. Now then I offer 你 a 寒冷 towel, maybe a 确实, 确实 寒冷 towel, 和 这 towel is saturated 与 水, so 你 could actually squeeze the 水 out of 那 和 cool 你的 身体 off. 和 我们的 Gedankin experiment is 对于 me to say, "Okay, where are 你 going to place the towel? How are 你 going to cool yourself off?" 和 I'm guessing 那 most of 你 会 think 那 the best way to cool yourself off 会 be to drape 那 towel over 你的 head, maybe 你的, neck over 你的 torso, 那 it 会 feel 确实, 确实 good, 和 they 会 cool 你 off.

安德鲁·休伯曼：

Well, 那's exactly the wrong approach if 你 want to cool off, 和 in fact, if 你 were to use 那 approach, 你的 体温 会 continue to 增加 even 更多, yes, even 更多 than had 你 not placed 那 寒冷 towel on 你的 head 或 你的 torso.

安德鲁·休伯曼：

和 here is why. Thermoregulation, meaning 你的 大脑和身体's ability to regulate 你的 internal core 温度 is somewhat like a thermostat, 和 那 thermostat resides in 你的 大脑. So if 你 think 关于 the thermostat in 你的 home 或 apartment, if it's too warm in 你的 home 或 apartment 和 你 were to take a bag of ice 和 to put it on 那 thermostat, what 会 the thermostat do? It 会 register the environment as artificially cool; it 会 think 那 the environment was actually much colder than it is. 和 so as a consequence, it 会 trigger a mechanism to further 增加 the 温度 in the room.

安德鲁·休伯曼：

和 你 have such a thermostat as well. It's called the medial preoptic area of the hypothalamus. The hypothalamus is a small region of 大脑 组织 关于 over the roof of 你的 mouth 和 a little bit in front of 那. So it's basically right behind 你的 nose 和 over the roof of 你的 mouth, 和 it's a collection of neurons. 那些 neurons have a lot of 不同的 functions 那 include things like the control of aggression, the control of sex behavior, the control of 温度 regulation, 和 so on.

安德鲁·休伯曼：

The medial preoptic area has connections 与 the rest of the 大脑, 或 areas within the 大脑, I 应该 say. 和 与 many areas within the 身体. It receives input 从 受体 in 我们的 皮肤 和 inside 我们的 身体 那 register 温度, 和 it acts as the thermostat. So if the surface of 你的 身体 is made cool, 你的 medial preoptic area 会 send signals by way of 激素 和 by way of chemicals 那 会 serve to 热 你的 身体 up.

安德鲁·休伯曼：

So what 这 means is 那 if 你 want to cool down, the last thing 你 want to do is to bring a 寒冷 surface of any kind, towel 或 splashing 水, to the majority of 你的 身体 surface. I 可能 be 非常, 非常 surprising to 你, 和 你 可能 say, "Wait, if I want to cool down, I 应该 jump 进入 a 寒冷 lake 或 something of 那 sort." 那's a 不同的 thing altogether.

安德鲁·休伯曼：

What I'll tell 你, 和 我们'll get 进入 这 in 更多 depth later, is 那 if 你 确实 want to cool down quickly 和 efficiently, 你 应该 leverage particular portals, meaning particular sites on 你的 身体 where 热 可以 leave 你的 身体 更多 readily, 和 where cooling 可以 have a dramatic 和 fast impact on 你的 核心体温. 可以 even save 你的 life if 你're going hyperthermic. 我们're going to talk 更多 关于 the 具体的 方案 to 减少 核心体温 对于 sake of 表现 和 avoiding hyperthermia later in the episode.

安德鲁·休伯曼：

Hyperthermia, of course, is a 非常, 非常 dangerous situation 因为 while 你的 身体 可以 drop in core 温度 somewhat 和 still be safe, 你 可以't 确实 增加 你的 体温 那 much 之前 你的 大脑 starts to cook 和 other organs start to cook, 和 by cook, I mean the cells actually start to die. So 你 have to be 非常, 非常 careful 与 the use of 热. 热 stroke is no joke. 人们 die 从 热 stroke all the time. 你 确实 want to avoid 那.

安德鲁·休伯曼：

一 way to avoid 那 is to cool the appropriate surfaces of 你的 身体, 和 the appropriate surfaces in 这 case are the upper cheeks, 或 I 会 say the upper half of the face, the 手掌 of 你的 hands 和 the bottoms of 你的 feet. I've talked 关于 这 on the podcast 之前 和 in the guest episode 与 Dr. Craig Heller, my colleague in the Biology Department at Stanford.

安德鲁·休伯曼：

但 just 非常 briefly, 这些 surfaces, the upper half of the face, the 手掌 of the hands 和 the bottoms of the feet are what 我们 call 无毛皮肤 surfaces. G-L-A-B-R-O-U-S, glabrous. 和 那些 surfaces are unique in 那 just below them, the vasculature is 不同的 than elsewhere in the 身体.

安德鲁·休伯曼：

Normally the passage of 血液 goes 从 arteries to capillaries to veins, 但 just beneath the 无毛皮肤 on the bottoms of the feet, the hands 和 the upper half of the face, 你 have what are called arterio-venous astomoses. 这些 are portals of 血液 那 go directly 从 arteries to veins, 和 in doing so, allow the 身体 to dump 热 更多 readily, 更多 quickly. So as it turns out, 那 if 你 are to cool the 手掌 of the hands, the bottoms of the feet 和 upper half of the face, 你 可以 更多 efficiently 减少 核心体温 对于 sake of offsetting hyperthermia 和 对于 improving athletic 表现 和 maybe even cognitive 表现.

安德鲁·休伯曼：

So 我们 会 return to the 具体的 方案 对于 doing 那 later in the episode. I'll give 你 a lot of details 关于 how to do 那, how to do 那 没有 the use of any fancy 或 expensive technology. There are some technologies 那 are now commercially available. 对于 instance, the so-called CoolMitt 那 会 allow 你 to do 那 与 maximum efficiency, 但 I'll also give 你 some at-home methods to do 这 either in the gym 或 on runs 或 对于 sake of cognitive work.

安德鲁·休伯曼：

So the 二 key themes again are understand 那 baseline 昼夜节律 和 温度, 和 understand 那 the best way to cool the 身体 is going to be by making sure 那 something 寒冷 contacts the bottoms of 你的 feet, the 手掌 of 你的 hands, 和 the upper half of the face. Ideally all 三 if 你的 goal is to lower 核心体温 quickly. 和 again, just cooling off the back of 你的 neck 或 the top of 你的 head 或 你的 torso 与 a towel is going to be the least efficient way to lower 核心体温 和 可能 even 增加 体温 under certain conditions.

安德鲁·休伯曼：

与 那些 二 points in 心智, 我们 可以 start to think 关于 directed deliberate 寒冷-exposure 方案. 和 there are a number of 不同的 reasons to use 主动冷暴露, 和 I want to separate 那些 out 对于 你. There are 寒冷 方案 那 have been tested in peer-reviewed 研究 那 are designed to 改善 心理表现. They are designed to 改善 things like resilience, 或 你的 grittiness, 或 你的 ability to move 通过 challenge, 或 to regulate 你的 心智 和 你的 internal state under conditions of 压力. 和 我们 可以 define 压力 非常 specifically as times when 肾上腺素, also called 肾上腺素, 和/或 去甲肾上腺素, also called noradrenaline, are elevated in 你的 身体. Forgive me 对于 the noradrenaline, 去甲肾上腺素, 肾上腺素, 肾上腺素 nomenclature. I didn't make 那 up. Turns out 那 every once in a while, scientists disagree. Imagine 那. 和 你'll get multiple scientists naming the same molecule 不同的 things.

安德鲁·休伯曼：

So 肾上腺素 和 肾上腺素 are the same thing. I 会 use them interchangeably. 去甲肾上腺素 和 noradrenaline are the same thing. I 会 use 那些 terms interchangeably. Noradrenaline 和 肾上腺素 are 经常 coreleased in the 大脑和身体. So they work as kind of a pair to 增加 我们的 水平 of agitation, 我们的 水平 of 专注 和 我们的 desire 和 我们的 ability to move.

安德鲁·休伯曼：

They are 经常 coreleased 从 不同的 sites in the 大脑和身体 与 多巴胺, a molecule 那 is commonly misunderstood as the molecule of pleasure, 但 is actually the molecule of motivation, reward, 和 pursuit. So 多巴胺, 去甲肾上腺素 和 noradrenaline tend to be 释放了 together under certain conditions. 和 today 你'll learn how 主动冷暴露 可以 be used to cause 增加 in the 释放 of several, if not all of 这些, in ways 那 可以 改善 你的 水平 of 注意力 和 你的 情绪.

安德鲁·休伯曼：

但 the key point is 那 你的 mental state is shifted when 你 are exposed to certain forms of 寒冷. 和 many 人们 use 主动冷暴露 specifically to shift their 身体 state as a way to train their mental state so 那 they 可以 better cope 与 压力 in real life. 和 by real life, I mean when life presents stressful events. 和 I 会 give 你 具体的 方案 as to how 你 可以 do 那. In other words, how 你 可以 become 更多 resilient 通过 the use of 主动冷暴露.

安德鲁·休伯曼：

Now, 因为 of the ways in which 主动冷暴露 可以 增加 这 category of chemicals called the catecholamines, 那 includes 多巴胺, 去甲肾上腺素 和 肾上腺素, it 可以 also be used to elevate 情绪 对于 long periods of time. 和 I'm going to discuss a 具体的 方案 那 has been shown to 增加 这些 chemicals anywhere 从 2.5x, so 250%, to as high as 500%, five times over baseline.

安德鲁·休伯曼：

Now, 你 可能 be asking whether 或 not 这 is a good thing to raise chemicals like 去甲肾上腺素 和 多巴胺 to such a great degree, whether 或 not 那's healthy 对于 us, whether 或 not they 可以 harm us. 但 it turns out 那 这些 elevations in 肾上腺素 和 多巴胺 are 非常 long-lasting in ways 那 人们 report feeling vast improvements in 情绪 和 vast improvements in 水平 of cognitive 注意力 和 能量. So by my read of the literature, 这些 seem to be healthy 增加 in 我们的 baseline 水平 of 这些 chemicals in ways 那 可以 确实 support us. So I'll give 你 a 方案 对于 那.

安德鲁·休伯曼：

Now, 那些 are some of the mental effects of 主动冷暴露. 但 主动冷暴露 has also been studied in animal models 和 in humans in the context of increasing 代谢. Even in converting certain 脂肪细胞 那 我们 call white 脂肪细胞, which are the ones where 能量 is stored — they're the ones 那 我们 通常 think of is kind of blubbery fat — to beige 或 棕色脂肪, which is thermogenic fat, meaning 那 it 可以 增加 核心体温 和 serves as kind of a furnace by which 我们 增加 我们的 core 代谢.

安德鲁·休伯曼：

So 与 a 非常 broad stroke, I 可以 say 那 white fat is generally the kind of fat 那 人们 want 更少 of, 和 beige fat 和 棕色脂肪 is generally the kind of fat 那 if 你're going to have 脂肪细胞, 和 你 certainly need 脂肪细胞, 那 你 want 更多 of. They are thermogenic, they help 你 stay lean. They actually serve as a reservoir 对于 heating 你的 身体 up if 你're ever confronted 与 a 寒冷 challenge. So 我们're going to talk 关于 how to use 寒冷 对于 代谢 as well. 和 of course, 人们 are using 主动冷暴露 to 减少 炎症 postexercise, to 减少 炎症 generally. 和 人们 are also using 寒冷 to 增强 表现 in the context of 力量 训练, in the context of 耐力 训练. 和 我们'll talk 关于 那些 数据 as well.

安德鲁·休伯曼：

但 where I'd like to start is 与 心理表现. 和 I'd like to detail what happens when 我们 deliberately expose ourselves to 寒冷. It's key to point out the word deliberate. If I don't say otherwise, then throughout 这 episode, if I say 冷暴露, I mean 主动冷暴露. 和 the reason I point 那 out is 那, as my colleague David Spiegel in the Department of Psychiatry at Stanford says, "It's not just 关于 the state 那 我们 are in, it's 关于 the state 那 我们 are in 和 whether 或 not 我们 had anything to do 与 placing ourselves 进入 那 state 和 whether 或 not 我们 did 那 on purpose 或 not." 和 what he 确实 means by 那 statement is 那 there are 重要 effects of what 我们 call mindset. Mindset was a topic discussed in the guest episode 与 Alia Crum some 周 ago. If 你 haven't seen 那 episode, I highly recommend it.

安德鲁·休伯曼：

和 the science of mindset tells us 那 if 我们 are doing something deliberately 和 我们 believe 那 it's going to be good 对于 us, it actually 可以 lead to a 不同的 set of physiological effects than if something is happening to us against 我们的 会 或 没有 我们的 control. Now, 这 is 不同的 than placebo effects. Placebo effects are distinct 从 mindset effects. If 你 want to learn 更多 关于 那 distinction, please see the episode 与 Alia Crum.

安德鲁·休伯曼：

但 again, when I talk 关于 冷暴露 in 这 episode, I'm talking 关于 主动冷暴露, meaning 那 你 are placing yourself 进入 a 寒冷 environment on purpose in order to extract a particular set of benefits. When 我们 talk 关于 主动冷暴露, almost 总是 那 means getting uncomfortable. 和 一 of the most common questions I get when discussing the use of 寒冷 对于 sake of mental 或 身体表现, 代谢, et cetera, is how 寒冷 应该 it be? How 寒冷 应该 the 水 be? How 寒冷 应该 the environment be? 和 I just 会 tell 你 now, 和 I'm going to say 这 again 和 again throughout the episode, 因为 it 会 continue to be true throughout the episode 和 long 之后 the episode is over, how 寒冷 depends on 你的 寒冷 tolerance, 你的 core 代谢, 和 a number of other features 那 there is simply no way I could know 或 have access to.

安德鲁·休伯曼：

So I 会 like 你 to use 这 rule of thumb. If 你 are using 主动冷暴露, the environment 那 你 place yourself 进入 应该 place 你的 心智 进入 a state of, "Whoa, I 会 确实 like to get out of 这 environment, 但 I 可以 stay in safely." Okay, now 那 可能 seem a little bit arbitrary, 但 let's say 你 were to get 进入 a warm shower ,和 it 会 feel 确实, 确实 nice, 和 你 were to start turning down the warm 和 turning up the 寒冷.

安德鲁·休伯曼：

There 会 be some threshold at which it 会 feel uncomfortable to 你. 和 if 你 were to continue to make a little bit colder than 那, 你 会 确实 want to get out of the shower, 但 你 were confident 那 你 could stay in 没有 risking 你的 health, 没有 risking a 心脏 attack. Now, 那's 非常 不同的 than jumping 进入 a 非常, 非常 寒冷 lake, 或 I've seen 这些 images of 人们 那 会 cut holes 进入 frozen-over lakes, 和 they'll get 进入 那 寒冷 水. If 你 are trained to do 那 和 你 have the right conditions, et cetera, 那 可以 be done reasonably safely. 但 那's certainly not what I 会 start 与. 和 对于 many 人们, 那 会 be too 寒冷. 和 indeed, some 人们 可以 go 进入 寒冷 shock 和 可以 die as a consequence of getting to 那 extremely 寒冷 水 非常 quickly.

安德鲁·休伯曼：

Now, 那's not to scare 你 away 从 主动冷暴露, it's just to say 那 there's no simple prescriptive of how 寒冷 to make the environment in order to extract maximum benefit 对于 mental 或 身体表现. So the simple rule of thumb is going to be place yourself 进入 an environment 那 is uncomfortably 寒冷, 但 那 你 可以 stay in safely. 和 你'll have to experiment a bit. 和 那 number, meaning 那 温度, 会 vary 从 天 to 天. It 会 vary across the 24-小时 cycle 因为 of 那 endogenous, meaning 那 internal rhythm, in 温度 那 I talked 关于 earlier. Low, early in the 天, rises 进入 the 下午, drops at 夜间. 你 可以 actually do 这 experiment if 你 like. Try getting 进入 a 冷水淋浴 at 11 o'clock at 夜间, if 你 want, versus try doing it in the middle of the 下午.

安德鲁·休伯曼：

It's quite a 不同的 experience. 和 by quite a 不同的 experience, I mean, it requires quite a 不同的 degree of resilience 和 leaning 进入 the practice. 你的 willpower 会 have to be higher, I suspect, late in the 天 compared to early in the 天. 但 那 会 vary, of course, between 个体 as well.

安德鲁·休伯曼：

So the most common question I get 关于 主动冷暴露 is how 寒冷 应该 the 水 be? 和 我们've answered 那 与 uncomfortably 寒冷 to the point where 你 want to get out, 但 你 可以 safely stay in. The 秒 most common question I get 关于 主动冷暴露 is whether 或 not 冷水淋浴 are as good, better 或 worse than 寒冷-水 immersion up to the neck, 对于 instance. I also get a lot of questions 关于 whether 或 not cryo chambers are better than all the others, et cetera, et cetera.

安德鲁·休伯曼：

I'm going to make all of 那 非常 simple 对于 你 by saying 寒冷-水 immersion up to the neck, 与 你的 feet 和 hands submerged also, is going to be the most effective. 秒-best 会 be 冷水淋浴. Third-best 会 be to go outside 与 a minimum amount of clothing, 但, of course, clothing 那 is culturally appropriate 和 那 会 allow 你 to experience 寒冷 to the point where 你 会 almost want to 发抖 或 start 发抖.

安德鲁·休伯曼：

Now, there are a number of 不同的 重要 constraints 那 are going to dictate whether 或 not 你 use 一 form of 冷暴露 或 the other. 对于 instance, some 人们 don't have access to 寒冷-水 immersion, they don't have access to ice baths 或 寒冷-水 tanks, 寒冷 ocean 或 寒冷 lakes, et cetera. In 那 case, showers 会 be the next best solution.

安德鲁·休伯曼：

I do want to emphasize 那 there have been 非常 few, if any 研究 of 冷水淋浴. 和 你 可以 imagine why 这 会 be the case. In a laboratory 你 want to control 对于 as many variables as 可能. So placing 人们 进入 a 寒冷-水 immersion 或 an ice bath up to the neck 和 insisting 那 they keep their 手和脚 under is 非常 easy to control. It means 那 everyone 可以 do 本质上 the same thing, whereas 与 冷水淋浴, 人们 are 不同的-sized bodies. Some 人们 are going to put their head under, some 人们 are going to, are going to lean forward. Measuring the amount of 寒冷-水 exposure on the 身体 is 非常 hard to do. 和 so there aren't a lot of 研究 of 冷水淋浴, 但 of course a lot of 人们 don't have access to 寒冷-水 immersion, so they have to use 冷水淋浴. 和 if 你 don't have access to both, of course, then going outside on a 寒冷 天 可以 be of benefit.

安德鲁·休伯曼：

但 I 会 point out 那 the 热 transfer 从 你的 身体 进入 水 is much higher, four times greater, if not even greater — depending on the 温度 of the 水 — in 水 as opposed to an 空气. So it's going to be much 更多 efficient to do 寒冷-水 immersion than anything else. 冷水淋浴 之后 那, 和 put yourself 进入 a 寒冷 environment 会 be the third best thing.

安德鲁·休伯曼：

I'm not going to get 进入 cryo chambers 因为 they carry quite a high degree of cost. 和 again, there aren't many 研究 of them. So if 你 have access to cryo chambers, I'm sure 那 the cryo-chamber facility has told 你 关于 all 这些 incredible benefits. 和 I don't doubt 那 some of 那些 benefits truly exist, 但 most 人们 just don't have the resources 或 the access to 那些. So 我们're going to leave cryo chambers out of today's discussion. 和 of course, I realized there was a fourth cate-

安德鲁·休伯曼：

Cryo chambers out of today's discussion. 和 of course I realize there's a fourth category of 冷暴露 out there. 人们 are wearing ice vests; believe it 或 not, 那些 exist. Ice underwear, yes, 那些 exist. 你 可以 look 对于 them on Amazon, if 你 like. They are putting 寒冷 packs in their armpits, 或 in their groin, 或 elsewhere in order to stimulate some of the effects of 寒冷 on mental 和 身体表现. I'm not going to address 那些 in too much detail today; they 可以 be efficient in certain ways, 但 as 你'll learn 关于 later in the episode, cooling the 手掌, the upper face 和 the bottoms of the feet is going to be far 更多 efficient. 和 unfortunately, I think most of the 人们 那 are using ice packs to 增加 their core 代谢 are not aware of the glabrous-皮肤 cooling, 和 how it 可以 be a 非常, 非常 potent stimulus.

安德鲁·休伯曼：

So 我们'll return to 那 later. Unless I say otherwise, I'm mainly going to be focusing on 寒冷-水 immersion 和 冷水淋浴. So let's talk 关于 方案 对于 增强 mental 健康与表现 using 主动冷暴露. What happens when 我们 get 进入 寒冷 is 那 我们 experience an 增加 in 去甲肾上腺素, in noradrenaline 释放, 和 in 肾上腺素 释放. The fact 那 冷暴露, deliberate 或 no, 增加 去甲肾上腺素 和 肾上腺素 in 我们的 大脑和身体 means 那 it is a 非常 reliable stimulus 对于 increasing 去甲肾上腺素 和 肾上腺素. 那's sort of an obvious statement, 但 那 obvious statement 可以 be leveraged to systematically build up what 我们 call resilience. Now, when 我们 experience a stressor in life, whether 或 not it's something bad happens in 我们的 relationship 或 something bad happens in the world, 和 我们 feel 压力, 那 压力 is the consequence of 增加 in 去甲肾上腺素 和 肾上腺素 in 我们的 大脑和身体. 非常 相似的, if not identical, to the kinds of 增加 那 come 从 主动冷暴露.

安德鲁·休伯曼：

So 主动冷暴露 is an opportunity to deliberately 压力 我们的 身体, 和 yet 因为 it's deliberate, 和 因为 我们 可以 take certain steps which I'll describe in a moment, 我们 可以 learn to maintain mental clarity. 我们 可以 learn to maintain calm while 我们的 身体 is in a state of 压力, 和 那 可以 be immensely useful when encountering stressors in other parts of life. 和 那's what 我们 call resilience 或 grit, 我们的 ability 或 mental toughness, 我们的 ability to lean 进入 challenge 或 to tolerate challenge while keeping 我们的 heads straight, so to speak. So 一 simple 方案 对于 increasing resilience is to pick a 温度 那's uncomfortable of shower 或 寒冷 immersion, 和 then to get in 对于 a certain duration of time, 和 then to get out. Now, it's 重要 to understand 那 人们 会 experience 不同的 水平 of 去甲肾上腺素 和 肾上腺素 释放 when getting 进入 寒冷 水.

安德鲁·休伯曼：

Some 人们, 因为 they dread the 寒冷 so much, 会 actually experience 去甲肾上腺素 和 肾上腺素 增加 even 之前 they get 进入 the 寒冷 水 或 under the 冷水淋浴. Now, 你 may have experienced 这, I've certainly experienced 这. I'm dreading it, I don't want to do it, 和 I have to force myself to do it. 和 indeed, 肾上腺素 和 去甲肾上腺素 和 its surges 可以 be thought of as sort of walls 那 我们 have to confront 和 go over. 和 I'd like 你 to conceptualize them 那 way, 因为 it allows us to build 方案 那 可以 be 非常 objective, 和 可以 allow us to monitor 我们的 progress in terms of building resilience. So 一 option is to simply say, "Okay, I'm going to force myself to get 进入 the 冷水淋浴 对于 一 分钟." How 寒冷? Again, uncomfortably 寒冷, 但 你 可以 stay in safely. 或, "I'm going to get 进入 the ice bath 对于 一 分钟."

安德鲁·休伯曼：

Ice baths are 非常 寒冷 inevitably, 和 what is also inevitable is 那 when 你 get 进入 the 寒冷, 你'll experience a surge in 肾上腺素 和 去甲肾上腺素. 那's nonnegotiable, 因为 it's mediated by 寒冷 受体 on the surface of 你的 身体 和 你的 皮肤 和 the way 那 they trigger the 释放 of 去甲肾上腺素 和 肾上腺素, not just 从 the adrenals, 从 the adrenal glands above 你的 kidneys, 但 also 从 regions of 你的 大脑 like the locus coeruleus, which cause 增加 in the tension 和 alertness, 和 从 other locations in 你的 身体 where 肾上腺素 和 去甲肾上腺素 are 释放了. In other words, 寒冷 is a nonnegotiable stimulus 对于 increasing 肾上腺素 和 去甲肾上腺素. Even if 你 are the toughest person in the world 和 你 love the 寒冷, 那 增加 in 肾上腺素 和 去甲肾上腺素 is going to happen. So the way to think 关于 去甲肾上腺素 和 肾上腺素 in 这 context of building mental resilience is 那 你 have 二 options.

安德鲁·休伯曼：

你 可以 either try to extend the duration of time 那 你 are in the 主动冷暴露, so going 从 一 分钟 to 75 秒 to 二 分钟, 和 so on, over a period of 天. 或 一 way to approach 这, 和 the way 那 I particularly favor, is to take the context of the 天 和 the moment 进入 account. Meaning 我们 have 不同的 水平 of grit 和 resilience on 不同的 天, 和 depending on the landscape of 我们的 life at the time, even the time of 天 那 我们're doing 这些 方案. 和 start to be able to sense the 释放 of 肾上腺素 和 去甲肾上腺素 in 我们的 大脑和身体, 和 see 那些 as walls 那 我们 want to climb over in order to build resilience, 和 to start counting the number of walls 那 我们 traverse 和 the distance between 那些 walls as 我们 do 主动冷暴露.

安德鲁·休伯曼：

Let me give 你 an example of the timed 方案 因为 那 一 is 非常 straightforward, 尽管 I do not think it is as powerful 对于 building mental resilience. The timed 方案 会 be, "Monday I do 一 分钟 of 主动冷暴露 at a given 温度. Wednesday I extend 那 by 50%, 和 Friday I do 主动冷暴露 对于 twice as long as I did on Monday. 和 if I were to continue 那 every 周, Monday, Wednesday, Friday, I 会 continue to either 增加 the duration, 或 I 会 lower the 温度 和 减少 the duration." 这 kind of thing, 非常 much like sets 和 reps in the gym. Now 那 option is 非常 objective, right? 你 could even log it in a book. 和 as 你 develop the ability to stay in 寒冷 temperatures, even progressively colder 和 colder temperatures, 对于 longer 和 longer periods of time, 你 会 become 更多 resilient.

安德鲁·休伯曼：

What do I mean by 那? Well, my operational definition of resilience is 那 你 are able to resist, escape 从 the stressor, the 寒冷, by virtue of 你的 willpower, which is 确实 你的 prefrontal cortex causing top-down control on 你的 reflexes 和 你的 limbic 系统 和 你的 hypothalamus, which are basically telling 你 to get out of 那 寒冷 水, get out of 那 寒冷 environment. 和 in doing so, 你 are basically getting better at controlling 你的 behavior when 你的 大脑和身体 are flooded 与 去甲肾上腺素 和 肾上腺素. 那's a 非常 reductionist way to explain resilience 或 grit 或 mental toughness, 但 it's a reductionist way of explaining it 那 is 非常 closely tied to the biology 和 to the psychology. 和 it is a fact 那 去甲肾上腺素 和 肾上腺素 释放 in the 大脑和身体 are the generic universal code 对于 stressor. There is no unique chemical signature 对于 不同的 forms of stressors, 那 is the only 一,

安德鲁·休伯曼：

尽管 of course there are other chemicals involved as well. So 你 could go 对于 time, 和 你 could try 和 减少 the 温度 和 增加 the time over a period of 天 或 周. Now 那's an attractive way to approach things, 但 the problem is 那 你 don't have an infinite amount of room 与 which to lower 温度 因为 eventually 你 会 get 进入 temperatures 那 are either so 寒冷 那 they are dangerous, 或 你 have to stay in 寒冷 temperatures 对于 such long periods 那 it becomes impractical, 因为 presumably 你 also have to take care of other aspects of 你的 life. 你 可以't just sit all 天 in the ice bath. Now, 对于 那 reason, I favor a 方案 in which 你 build mental resilience 和 mental toughness 通过 二 不同的 types of 方案. The 首先 一 involves counting walls.

安德鲁·休伯曼：

Now, what do I mean by walls? I mean the sensation of "No, I don't want to do 这." 和 the idea 或 the sensation in 你的 大脑和身体 那 你 actually want to leave 那 environment 和 go warm up. Now again, 对于 some 人们 那 会 be even 之前 getting 进入 the ice bath 或 冷水淋浴. So if 你 are feeling 非常 resistant to getting 进入 the ice bath 或 冷水淋浴, 和 你 manage to do 那, 那's going over what I 会 call 一 wall. Okay?

安德鲁·休伯曼：

Then 对于 some period of time, 你 可能 actually feel comfortable in the ice bath, 寒冷 水 或 冷水淋浴, 和 你 feel like 你 could stay there 对于 some period of time. 那 你 could stay there 对于 a 分钟 或 二 分钟, 但 inevitably the next wall 会 arrive, 和 I 会 encourage 你 to pay 注意力 to when 那 next wall arrives, 和 actually having an awareness, 那 so-called interoceptive awareness, as 我们 call it, of when 那 next surge in 肾上腺素, 肾上腺素, comes, 或 whether 或 not it reaches a certain threshold in 你的 大脑和身体 那 你 feel 你 want to get out, 和 你're able to stay in 对于 even just 10 秒 longer, 那 means 你've traversed yet another wall.

安德鲁·休伯曼：

和 if 你 continue to stay in 那 寒冷 environment, 你'll find 那 the next wall 会 come, 和 the next wall 会 come. Now eventually, of course, 你 会 get 非常, 非常 numb, depending on how 寒冷 it is, 和 你 could also place yourself 进入 danger. So 你 have to maintain cognitive control, counting 这些 walls, traversing 这些 walls, 但 getting out at some point, of course. So my favorite 方案 对于 building mental toughness, aka grit, aka resilience, is to take 进入 account 那 some 天 just getting 进入 the ice bath 或 冷水淋浴 represents a wall, some 天 it doesn't. Some 天 你 get in 和 你 feel like 你 could go 10 分钟, other 天 你 get in 和 你 feel like 你 could only go a 分钟. 和 setting a designated number of walls 之前 你 start the 方案 is going to be 非常 beneficial here.

安德鲁·休伯曼：

So 你 say, "As long as I 可以 do it safely, I'm going to do 三 walls today. The 首先 wall is getting in, the 秒 wall 会 arrive when it arrives, 和 the third wall 会 arrive when it arrives, 和 I'll get over 那 wall, 和 then I'll get out." The next 天 你 可能 do five walls, the next 天 你 可能 do 三 walls again, 但 你 可能 lower the 温度. 这 gives 你 tremendous flexibility, 和 indeed, it gives 你 much 更多 latitude to be able to use the same temperatures in 不同的 ways, 或 to 减少 the 温度 only a little bit 和 still get a lot of stimulus, meaning a lot of 结果 out of a given 方案. Whereas 人们 who are just going 对于 温度 和 time, eventually become 寒冷 adapted, they get 非常, 非常 good at doing 三 分钟 或 six 分钟 或 even 10 分钟 at a given 温度. 和 so then they feel like they have to lower the 温度 even 更多 和 even 更多, 和 eventually they just bottom out; there's nowhere else to go.

安德鲁·休伯曼：

There's nowhere to get improvements out of the 方案, at least not in terms of mental resilience. Of course, there's still the positive effects on 炎症 和 代谢, et cetera, 那 我们'll talk 关于 in a little bit. 但 the key thing here is to design 方案 那 are going to work 对于 你 over time. 和 对于 你 非常, 非常 hardy, 非常, 非常 tough guys 和 gals out there 那 可以 get right 进入 an ice bath 或 非常, 非常 寒冷 immersion, 和 你 可以 just grind it out 对于 six 或 10 分钟, 或 你 可以 even do 那 by remaining peaceful, well, 更多 points to 你, 但 guess what? 那's the equivalent of already having loaded up the barbell 与 600 pounds 和 done 你的 10 reps — there's not a whole lot 更多 variable space 与 which to get benefits 从 那 stimulus.

安德鲁·休伯曼：

和 in the weight room, 人们 understand 那 你 可以 adjust, 对于 instance, the speed of the movement, 或 你 可以 start combining 那 movement 与 pre-exhaustion, et cetera. 与 冷暴露, 你 don't have as much variable space to play 与. So if 你的 goal is to build resilience, either go 对于 time as a function of 温度, 或 what I suggest is to start recognizing 这些 walls as an experience of resistance in 你 和 going over 那些 walls, set a certain number of walls 那 你're going to go over on a given 天, 和 do 那 at a given 温度, 和 then to mix it up. 和 ideally, 你 可能 even throw in 一 更多 wall at the end if 你're 确实 feeling bold 和 brave, 因为 那's going to build out further resilience. 但 if 你 want 冷暴露 to work 对于 你 对于 sake of building up resilience 和 mental toughness over time, 你're going to want to vary 这 parameter space in some sort of way, 和 你 don't have to be super systematic 关于 it.

安德鲁·休伯曼：

那's the beauty of 这 kind of approach 因为 你're relying on the fact 那 那些 walls 确实 represent times in which 你 are forcing 你的 top-down control, 你的 prefrontal cortex, to clamp down on 你的 reflex 和 你的 learning behavioral control in the context of 你的 身体 having elevated 水平 of 这些 catecholamines, 去甲肾上腺素 和 肾上腺素. 和 那 translates to real life in a much 更多 realistic way, I believe, 因为 in real life 你're not 确实 engaging in stressors 对于 a given amount of time, 那 你 know how long it's going to last, 和 你 know the context. No, most stressors arrive in the form of surprises 我们 don't like. Text messages 那 deliver bad news, information 关于 the outside world 或 real world 和 online interactions 那 send 我们的 系统 进入 a state of 增加了 去甲肾上腺素 和 肾上腺素. 和 if 你 start to think of 那些 as walls 那 你 可以 tolerate 和 climb over while staying calm 和 clear of 心智, then 你 可以 确实 imagine how the ice bath 和 other forms of 冷暴露 are 确实 serving to train 你 up 对于 real-life stressors.

安德鲁·休伯曼：

Okay, the next question 那 I 总是 get is, "What 应该 my mental state be while I'm exposing myself to 这 uncomfortable yet safe condition of 寒冷?" Well, 你 have 二 options, 和 there are probably other options as well. 一 is to try 和 calm yourself to remain as mentally still as 可能. The other is to lean 进入 那 challenge, 和 so to grind it out. 和 here, I have to say 那 这 is a lot like teaching someone to drive on a gravel road. 对于 any of 你 那 have driven on a gravel road, 你 know 那 there is no optimal speed 对于 all gravel roads. It depends on the density of the gravel, et cetera, 和 the vehicle, et cetera. So 对于 instance, on some gravel roads, when 你 start to drive, 和 the dust starts to kick up, 你的 best option is to drive fast 和 put 那 dust cloud behind 你.

安德鲁·休伯曼：

On other gravel roads, if 你 try 和 do 那, the dust actually kicks up 大约 the vehicle, 和 it makes it hard to see, 和 sometimes 你 have to slow down. The same thing is true 对于 getting 通过 主动冷暴露. Sometimes it's easier to calm yourself. 一 way to do 那 is 通过 double inhales 通过 the nose 和 extended exhales 通过 the mouth. 或 simply by trying to control 你的 breathing 和 减少 the pace of 你的 breathing 和 增加 the volume of 你的 breathing. I have to say 那 everyone experiences a shortening of breath when they get 进入 uncomfortably 寒冷 水; 那 is a universal physiological response. Everyone also experiences a 30 to 80% 降低 in cognitive function, in particular of the frontal cortex. The 代谢 of 你的 frontal cortex goes down, the 代谢, meaning the activity of 大脑 areas associated 与 压力 和 panic, goes way up.

安德鲁·休伯曼：

和 so anchoring 你的 心智 in cognitive activities as 你 get 进入 the 寒冷 可以 be 非常, 非常 helpful 对于 maintaining clarity of 心智. In fact, 一 thing 那 I sometimes recommend is 那 人们 try 和 engage in some sort of cognitive 运动 while in the 寒冷, not as a form of distraction, 但 as a way to maintain clarity of thinking, 和 to learn how to do 那 when the 身体 is flooded 与 all 这些 chemicals 那 make us stressed. So 对于 instance, 你 could do math problems, 和 not 二 plus 二 equals four, not 三 times 三 equals nine, 但 things 那 require a little bit 更多 专注 和 注意力, working memory, 和 so forth. 你 could also start to have thoughts 那 你 deliberately impose a full-sentence structure on, 那's actually quite tough. 你 could try 和 recall 具体的 bouts of information 那 are challenging.

安德鲁·休伯曼：

这 is teaching 你的 心智 how to stay online, 或 rather, I 应该 say, 这 is 你 teaching 你的 prefrontal cortex how to stay engaged, while 你 have high 水平 of 压力 in 你的 身体. Years ago, I had a friend who works in the neuroscience world, 研究 neuroscientist, who was obsessed 与 这 非常 bizarre sport 那 I don't necessarily recommend at all, which is the combination of boxing 和 chess. 你 may have seen 这 on YouTube, where 人们 会 box 大约, legitimate boxing 大约, they're sparring all-out 经常. 和 then at the end of the round, instead of resting in the corner, they actually sit down 和 play chess, 和 then they go back to boxing, 和 back to chess. Again, not a sport 那 I recommend, 但 the reason he was obsessed 与 这 is 因为 he 研究 the impact of 压力 on cognitive 表现.

安德鲁·休伯曼：

和 what 那 particular, 非常 bizarre sport was doing was toggling back 和 forth between 不同的 states of 心智. Now it's used both to 增加 cognitive clarity 对于 the fighter when they box, 因为 staying calm 和 clear thinking is 非常 重要 to winning boxing matches — believe it 或 not, it's not an all-out rage, it's a 非常 calculated game of mental chess 和 physical chess 那's quite high stakes, as 你 可以 imagine. It's also used in some circles as a way to teach 人们 how to engage in cognitive 表现 when their 身体 is simply filled 与 压力. So in the boxing-chess example, the replacement 对于 the 寒冷 水 is actually the boxing, right? It's the thing 那's supposed to induce the 压力, 因为 getting hit is stressful, 和 the risk of getting hit is stressful 对于 most 人们. So again, if 你 think 关于 主动冷暴露 as a way of just systematically 和 reliably inducing 肾上腺素 和 去甲肾上腺素 释放 in delivering 压力, well then 这 idea of maintaining cognitive clarity 和 actually engaging in cognitive tasks while in the ice bath 或 冷水淋浴 可以 actually be 非常 beneficial.

安德鲁·休伯曼：

Even though it 可能 sound a little bit silly, 你 are 确实 训练 up 你的 ability to keep 你的 大脑 working when the reflex is to shut down the parts of 你的 大脑 那 are involved in deliberate planning 和 thinking. Now, another 重要 aspect of 主动冷暴露 那 I rarely, if ever here discussed, 但 is vitally 重要, is whether 或 not 你 move 大约 或 not. Here's the reason, when 你 get 进入 寒冷 水, 和 你 remain there 对于 some period of time, 你的 身体 is generating 热, 和 那 热 generates what's called a thermal layer 那 surrounds 你的 entire 身体. So if 你 stay still, 你 are actually warmer than if 你 move 大约. 你 可以 try 这 the next time 你're doing 你的 主动冷暴露. If 你're submerged up to the neck, sit there 对于 关于 10, 30 秒 和 be 非常, 非常 still of 身体.

安德鲁·休伯曼：

In fact, 这 is the way 那 most 人们 start to do 主动冷暴露. They give 这 非常 stoic look, they don't blink, they look 非常 peaceful. Some of them even look tough, 或 they make a 非常 emotional face, 和 so it looks like they're, well, they're 确实 tough, 但 they are so still 那, believe it 或 not, they are not providing the most potent stimulus. If they 或 你 were to move 大约 in 那 水, what 会 happen is 你'd break up the thermal layer, 和 那 你 actually experience 那 as much colder. So if 你 确实 want to push the resilience aspect, 或, 对于 instance, if 你 want to use a given 温度 那 你're comfortable in, 但 那 你 want to 增加 the stimulus, 和 你 want to get some 更多 benefit 对于 mental resilience 训练, well then get 进入 the 寒冷 水, move 你的 身体 大约 continuously, 但 try 和 keep 你的 心智 still, 或 even do some sort of cognitive task.

安德鲁·休伯曼：

So as 你're starting to realize, there are a bunch of 不同的 variables 那 你 可以 play 与 while maintaining the same 温度 of 水, 和 in doing so, 确实 keep 你 in the zone of what 应该 和 absolutely has to be safe 对于 你, 没有 having to just continually drop the 温度 从, say, 60 degrees to 55 to 40 to 33 因为 as I mentioned 之前, eventually 你're going to bottom out. So if 你're 一 of 那些 人们 那 likes to look tough 或 确实 relaxed while 你're in the ice bath 或 寒冷-水 immersion, just realize 那 你're actually cheating yourself out of part of the stimulus. Keep 那些 limbs moving, 和 of course, limbs under the 水, feet 和 hands, is going to be a 更多 potent stimulus than 手和脚 out, 对于 reasons 那 应该 be obvious based on what 我们 talked 关于 in terms of glabrous-皮肤 cooling.

安德鲁·休伯曼：

So keep 那些 submerged, move 你的 身体, pedal, maybe move 你的 knees up 和 down, pedal 你的 feet, 和 trust me, it's going to feel a lot colder than were 你 to remain stone still. Another 非常 common question is, "How 经常 to do 主动冷暴露?" It's tough to make a recommendation on 那 based on any peer-reviewed 研究, 尽管 there are a few in humans 那 point to a threshold of 11 分钟 total per 周. So 那's total throughout the 周, divided 进入 二 或 four sessions of 二 或 三 分钟 或 so. Now 那 11-分钟 cutoff is not a strict threshold 和 is actually geared 更多 towards 增加 in 代谢. 我们'll get 进入 这 a little bit later in the episode, 但 I think the 11-分钟 threshold, meaning 11 分钟 total of 主动冷暴露 per 周, is a pretty good number to use if 你 need a number in order to keep 你 consistent.

安德鲁·休伯曼：

但 as 我们 talked 关于 earlier, some of 你 are going to be in the ice bath 或 寒冷 immersion 或 冷水淋浴 对于 一 分钟. Others of 你 会 be in there 对于 10 分钟, depending on how frequent 和 how high, if 你 会, 那些 walls of 肾上腺素 are coming. So 对于 some of 你, getting 进入 a 冷水淋浴 对于 三 分钟 total 对于 the whole 周 会 represent a tremendous achievement in terms of willpower 和 overcoming the resistance to doing 那, overcoming 那些 walls. 对于 others of 你, 三 分钟 is nothing.

安德鲁·休伯曼：

So what do I recommend? I recommend 那 你 get at least 11 分钟 total per 周, 但 at the point where 11 分钟 total per 周 is 非常 easy 对于 你, 或 is no longer representing a significant mental challenge, meaning 你're not experiencing many of 这些 walls — 你're excited to get 进入 the 冷水淋浴 或 immersion, 你're going 通过 it easily, 你're cruising, basically — then I 会 say either lower the 温度, safely, of course; extend the duration, safely, of course; 或 增加 the frequency so 那 你're doing 这 perhaps every 天, 或 maybe five 天 a 周, 或 三 天 a 周.

安德鲁·休伯曼：

I personally get tremendous benefit 从 doing 主动冷暴露 三 times a 周 和 using the walls method 那 I described earlier as my gauge 对于 how long to stay in. 和 通常 那 means 那 I'm staying in 对于 anywhere 从 二 分钟 to six 分钟 per session, 和 那 averages out to 关于 11 to 15 分钟 total per 周. So again, I do not think 那 你 need to be super strict 关于 这些 guidelines. It's most 重要 when embracing a 方案, A, 那 你 do it safely, 但 secondarily 那 你 do it consistently. So find what 你 可以 do consistently, 和 then vary the parameters 那 会 allow 你 to continue to do 主动冷暴露 consistently, regardless of whether 或 not 你 have access to a shower 或 寒冷 immersion, et cetera. Okay, so 我们've been talking 关于 mental effects 和 the use of 主动冷暴露 对于 sake of building resilience, which I do believe 可以 be tremendously powerful.

安德鲁·休伯曼：

Look, it's no coincidence 那 the screening 和 the 训练 对于 Navy SEALs involves a lot of exposure to 寒冷 水. 一 could argue 那 it is deliberate 因为 they elect to go to BUD/S, 但 when they get 进入 the 寒冷 水 at BUD/S is dictated by the instructors. 和 the reason they use 寒冷-水 exposure as the stressor is 那 it does offer considerable leeway in terms of duration 和 温度 in terms of how 你 可以 use it as a stressor. Whereas things like 热 don't offer much variable space, as 我们 say. There isn't a lot of room beyond which 你 start injuring 或 even killing 人们 by using 热. So there are a lot of forms of stressors out there, 但 寒冷 is 一 那 我们 可以 titrate, 那 我们 可以 adjust in ways 那 可以 allow us to continually build up, 和/或 maintain mental toughness.

安德鲁·休伯曼：

Now, 主动冷暴露 also has many effects on chemicals other than 去甲肾上腺素 和 肾上腺素. Most notably the neuromodulator 多巴胺, which is involved in elevating 我们的 情绪, making us feel energized, 和 增强 我们的 ability to 专注, 和 那 has a lot to do 与 how 多巴胺 engages us in motivated states, tends to narrow 我们的 thinking in 我们的 behavior 进入 a particular trench of goal-directed behavior. If 你 want to learn 更多 关于 多巴胺, 你 可以 learn a lot 关于 多巴胺 in 我们的 episode 关于 多巴胺. It's at Hubermanlab.com; 你 可以 find it. It's a 二-和-a-half-小时-plus deep dive 进入 all things 多巴胺, 专注, motivation, et cetera. 主动冷暴露 has a 非常 powerful effect on the 释放 of 多巴胺 in 我们的 大脑和身体, 和 这 is 一 of the main reasons why 人们 continue to do 主动冷暴露.

安德鲁·休伯曼：

Basically, it makes us feel good, 和 it continues to make us feel good even 之后 我们 get out of the 寒冷 environment. In fact, some 人们 会 say they don't feel good in the 寒冷 environment, it's all 压力 对于 them, 但 afterwards they feel great. 一 of 我们的 previous guests, Dr. Anna Lembke, who's a medical doctor at Stanford University School of Medicine, she's a close colleague of mine, described the use of 多巴胺 in her book "多巴胺 Nation," an incredible book 关于 addiction 和 多巴胺, I 应该 mention, 和 the use of 多巴胺 elicited by 寒冷-水 exposure by 一 of her patients. What I'm referring to is the fact 那 一 of her patients helped themselves get 和 stay sober off drugs by using 主动冷暴露 to 增加 多巴胺. So a healthier form of 多巴胺 释放 than they were engaged in prior to getting sober.

安德鲁·休伯曼：

Now, the basis 对于 多巴胺 释放 in response to 冷暴露 is 那 the catecholamines, 去甲肾上腺素, 肾上腺素, 和 多巴胺, tend to be 释放了 by the same sorts of stimuli. 但 most stressors 和 in particular things 那 evoke 压力 或 我们的 feelings of 压力 internally 那 我们 don't like, do not 增加 多巴胺. They only 增加 去甲肾上腺素 和 肾上腺素, 但 主动冷暴露 seems to cause a dramatic 增加 in 多巴胺, 和 这 has actually been substantiated in a 确实 beautiful 研究 entitled "Human physiological responses to immersion 进入 水 of 不同的 temperatures." The 首先 author is Šrámek; I'm almost certainly pronouncing 那 poorly, 和 if not incorrectly, S-R-A-M-E-K. 这 was published in the European Journal of Applied Physiology, in the year 2000. 确实, a beautiful 研究; I love 这 研究. They took 人们 和 they had them sit in chairs under 水, 但 their head was out, 和 they were ... so they were immersed up to the neck in either of 三 不同的 temperatures: 32 degrees Celsius, which is 89 degrees Fahrenheit; 20 degrees Celsius, which is 68 degrees Fahrenheit; 或 14 degrees Celsius, which is 57.2 degrees Fahrenheit.

安德鲁·休伯曼：

So not super 寒冷, 但 then what they did is they measured 人们's 核心体温 throughout. They measured their 代谢, 和 they looked at serum 水平 of things like 去甲肾上腺素, 肾上腺素, 多巴胺, 和 cortisol — serum meaning within the 血液. So a 确实 nice 和 quite thorough 研究. There were not a huge number of 受试者 in the 研究, 但 nonetheless, it was a 非常 thorough 研究 in terms of the number of variables 那 they explored. So I just want to briefly highlight some of what they saw, 或 what they observed in 这 研究. 首先 of all, the groups were in the 水 of a given 温度 对于 一 小时, which is much longer than most of the deliberate 寒冷-exposure 方案 那 anyone is using at home. I mean, maybe 你're taking 一-小时-long 冷水淋浴, maybe 你're getting 进入 the ice bath 对于 an 小时, 尽管 I don't recommend 那. I think 你'd probably get badly hypothermic.

安德鲁·休伯曼：

或 maybe 你're getting 进入 a 寒冷-水 immersion 对于 some period of time, 但 I have a hard time imagining 那 it 会 be an 小时, 和 I don't suggest 那 if it's 非常 寒冷. So 这 研究 focused on actually somewhat moderately cool temperatures, not what I think most 人们 会 consider 非常, 非常 寒冷 temperatures, 但 extended the duration 对于 quite a while. So again, 32 degrees Celsius, 20 degrees Celsius, 或 14 degrees Celsius. Here's what they observed. The group 那 was immersed up to the neck in 32 degrees Celsius — 那 is 89 degrees Fahrenheit — 水 did not experience a shift in 代谢, nor a significant 增加 in 多巴胺, 去甲肾上腺素 或 这些 other catecholamines. The group 那 was in 20 degrees Celsius, meaning 68 degree Fahrenheit 水 对于 an 小时 experienced a 93% 增加 in metabolic rate, which is remarkable given 那 the 水 wasn't 那 寒冷, 和 yet an 小时 is a pretty long time to be in there.

安德鲁·休伯曼：

和 again, it speaks to the dramatic effect of 热 transfer 那 水 has, which I mentioned earlier, as opposed to being out in the 空气 at 68 degrees; it 会 certainly not cause 那 增加 in metabolic rate. The group 那 was at 14 degrees Celsius — meaning 57.2 degrees Fahrenheit — 水 对于 an 小时 experienced a 350% 增加 in 代谢, so huge 增加 in 代谢. Now, the most interesting 数据 to me, at least in terms of mental effects of 主动冷暴露, were 那 the plasma, 或 serum, 水平 of 去甲肾上腺素 in the 血液 增加了 530%. 这些 are huge 增加 in 去甲肾上腺素, so it suggests 那 这 is a stressful stimulus, at least neurochemically speaking — stressful, despite the fact 那 it's not super, super 寒冷. 尽管 57.2 degrees Fahrenheit, 14 degrees Celsius, is not a warm environment, 但 it's not an ultra, ultracold environment, 但 an 小时 is a 非常 long time to be in there.

安德鲁·休伯曼：

The 受试者 also experienced a 250% 增加 in 多巴胺 concentrations, which, while not 530% as it was 与 去甲肾上腺素, is still a 非常 large 增加 in baseline 水平 of 多巴胺. 和 what was interesting is 那 那些 增加 in 多巴胺 persisted 对于 a 非常 long period of time afterwards, even out to 二 小时, 和 they stopped the 研究 之后 120 分钟 of getting out of the 寒冷. 但 nonetheless, 这些 增加 in 去甲肾上腺素 are huge 和 long-lasting, 和 这些 增加 in 多巴胺 are 非常 large 和 long-lasting. 和 I do believe 那 这些 documented effects in humans explain much of the enhancement of 注意力, 和 of feelings of well-being 和 情绪, 那 人们 通常 experience 之后 doing 主动冷暴露.

安德鲁·休伯曼：

和 the reason I say 那 is 那 if 你 were to go back to the episode 那 I did on 多巴胺, 或 你 were to go back to the episode 那 I did 与 Dr. Anna Lembke on addiction 和 多巴胺, what 你 会 find is 那 增加 in 多巴胺 of the sort evoked by 主动冷暴露 are actually 非常 相似的 to the kinds of 增加 in 多巴胺 那 are elicited by things like nicotine, 或 从 other behaviors 那 are known to be addictive 和 bad 对于 us 因为 they lead to other effects on the 大脑和身体 那 我们 simply don't want.

安德鲁·休伯曼：

和 yet, 主动冷暴露, provided it's done safely, 可以 create 相似的, if not greater 增加 in 多巴胺 那 are not just fleeting, 那 don't just occur 期间, say, the consumption of some deleterious drug 或 activity, 但 那 are 非常 long-lasting, 和 那 可以 be leveraged toward activities other than 主动冷暴露. So I want to emphasize 这: I'm not suggesting 那 人们 do 主动冷暴露 对于 an 小时 a 天. 和 unfortunately, there are not many 研究 yet exploring how shorter, colder 温度 environment exposure, say 一 分钟 或 三 分钟 或 six 分钟 at 55 degrees, 或 at 50 degrees, whether 或 not 那 leads to 相似的, greater, 或 reduced 水平 of 多巴胺 in the 大脑和身体. 和 yet almost everybody who does 主动冷暴露 会 say, "Yeah, it was stressful. I didn't enjoy it," 或, "I eventually grew to like it, 但 ..." 那 "... I 总是 feel better afterwards. 和 then 那 feeling lasts a 非常 long period of time." 和 I think it's almost certain 那 那些 experiences 那 人们 report relate to 这些 增加 in 多巴胺 和, in concert 与 the 增加 in 去甲肾上腺素, also explain the other effect 那's commonly reported, which is an enhancement in mental acuity 和 the ability to 专注. Now here 我们 可以 extrapolate to the 研究 那 I discussed at the early part of the episode, where I was talking 关于 the use of short, 15-分钟 运动, kind of moderate-intensity 运动, 和 how 那 was shown to 增加 水平 of 能量 和 mental acuity in 这些 working memory visual 注意力 tasks. 和 there again, 我们 have to assume somewhat 因为 they weren't doing neurochemical measurements, 但 我们 可以 reasonably assume 那 那些 improvements in cognitive 表现 were

第1部分（共3部分）结束 [00:33:04]

安德鲁·休伯曼：

Reasonably assume 那 那些 improvements in cognitive 表现 were due at least in part to the 增加 in catecholamines known to accompany moderate intensity zone 2 cardio. So, what 你're starting to see here is a theme. The theme is 那 virtually any stimulus 那 delivers 更多 去甲肾上腺素, 肾上腺素 和 多巴胺 进入 我们的 系统 会 sharpen 我们的 mental acuity 和 elevate 我们的 情绪 和 会 do so 对于 some period of time. 主动冷暴露, it turns out, is a 非常 potent way to 增加 这些 catecholamines, 这 category of chemicals 和 thereby to 改善 情绪, mental acuity 和 水平 of alertness, 和, as 我们'll next see, it not only has 那 effect, which 可以 be 非常 beneficial 对于 many 人们 in a bunch of 不同的 circumstances, 但 it also has the positive effects 那 many 人们 seek in terms of 代谢, in lowering 炎症 in the 身体 和 other physiological effects as well.

安德鲁·休伯曼：

和 forgive me, I was almost ready to move on to effects of 主动冷暴露 on 代谢 和 炎症 和 so forth, 但 I neglected to point out 一 of the other 非常 interesting aspects of the 研究 showing 主动冷暴露 可以 增加 去甲肾上腺素 和 多巴胺. Which is 那 they observed no significant 增加 in the 压力 激素 cortisol. 和 那 is both surprising, interesting 和 重要 因为 what it means is 那 the quality of 压力 那 主动冷暴露 is creating in the 身体 is 可能 to be 一 of what 我们 call use 压力. Hans Selye, the great physiologist, won a Nobel Prize 对于 distinguishing between distress, which is 压力 in the 大脑和身体 那 causes the 释放 of things like cortisol, along 与 the other catecholamines, 和 那 我们 experience as negative, happening to us, 和 可以 lead to negative health outcomes.

安德鲁·休伯曼：

和 he distinguished 那 从 eustress, which was 压力 那 我们 now understand is associated 与 增加 in things like 去甲肾上腺素 和 多巴胺, 但 no 增加 或 minimal 增加 in cortisol, 和 那 可以 lead to positive health outcomes. So it appears 那 主动冷暴露 可以 create what 我们 call, 或 what Hans Selye called, eustress. In other words, it 可以 create a condition in the 大脑和身体 in which 我们 are stressing ourselves, 我们 are 训练 up resilience, 和 yet, 我们 are creating a neurochemical milieu 那 actually has many health benefits. Now, I'd like to shift 我们的 注意力 to the effects of 主动冷暴露 on 代谢. 和, I'd like to start by detailing a 研究 那 was performed on humans 和 published just at the end of last year. The title of the 研究 is "Altered 棕色脂肪 thermoregulation 和 enhanced 寒冷-induced thermogenesis in young, healthy, winter-swimming men."

安德鲁·休伯曼：

和 I 应该 point out 那 while the 研究 was only performed on male 受试者, there's no reason to think 那 the effects 那 they discovered 会 only pertain to men. I 会 hope 那 they 会 also do a 研究 on women at some point in the future, 但 the effects 那 they describe are 非常 basic core physiological processes. What they did is they looked at 主动冷暴露 in 这 group of young men, 和 they used 那 11-分钟 threshold per 周. So in other words, they had them get 进入 寒冷 水 对于 approximately 11 分钟 per 周. 和 again, 那's 11 分钟 total per 周. They divided 那 进入 二 sessions. 尽管 in speaking 与 the 首先 author of 这 研究, Dr. Susanna Søberg, I learned 那 it probably is not 重要 那 it be 二 sessions, it could be 三 或 even four sessions, as long as it reaches 那 11-分钟 threshold.

安德鲁·休伯曼：

What they discovered was 那 by going 进入 这些 寒冷 environments, in 这 case 寒冷-水 immersion up to the neck 对于 11 分钟 total per 周, 那 这些 men experienced 增加 in so-called 棕色脂肪 thermogenesis — I'll talk 更多 关于 what 那 is in a moment — 和 增加 in 核心体温, 那 translate to 增加 in core 身体 代谢. Now, the overall 增加 in core 身体 代谢 那 they experienced were not extremely large. They were statistically significant, 但 they weren't extremely large. 然而, the changes in 棕色脂肪 stores are perhaps what's most interesting 关于 这 研究, 和 I'll tell 你 why. The metabolic 增加 of 主动冷暴露 are both acute, meaning happening in the short-term, when 你 get 进入 the 寒冷, 和 immediately 之后, 一 does experience an 增加 in core 代谢. 你 burn some calories, in other words. 和 while 那些 可能 not be 非常 significant 增加, 或 I 应该 say they 可以 be statistically significant, 但 they are not enormously large numbers of calories burned.

安德鲁·休伯曼：

The longer-lasting effects of 主动冷暴露 on 代谢 seem to take place by changes 那 occur in the types of fat 那 我们 store in 我们的 身体 和 the way 那 那 fat impacts 我们的 代谢 at other times throughout the 24-小时 cycle. 这 actually has a somewhat anecdotal basis, in particular in Scandinavia. I don't speak Swedish, nor I speak Danish, nor do I speak Norwegian, 但 I do have Danish relatives, 和 they were able to help me decipher a common Swedish saying, which 本质上 translates to the fact 那 in preparation 对于 the summer, they say, 一 应该 expose themselves to warm environments so 那 一 is comfortable in warm environments in the summer. 那's 一-half of 这 traditional Swedish 和 also Danish saying. The other half of 这 traditional Danish Swedish saying is 那 in preparation 对于 winter, in order to not feel too 寒冷 in 寒冷 environments, 一 应该 prepare 对于 那些 in the fall by not wearing a jacket 和 exposing oneself to 寒冷 environments.

安德鲁·休伯曼：

Now of course, 这 is just anecdotal cultural lore, 但 it actually has a physiological basis, which is by exposing oneself to 寒冷 environments on a repeated basis in anticipation of exposure to 更多 extreme 寒冷 environments, 一 可以 feel 更多 comfortable in 那些 extreme 寒冷 environments. 和 那's exactly what they observed in 这 研究 by Søberg at al. The men felt 更多 comfortable in extreme 寒冷 if they had trained 通过 主动冷暴露. Which 可能 not seem surprising at all, 但 based on what 我们 talked 关于 earlier, whereby 主动冷暴露 evokes 这 discomfort 和 这 experience of 去甲肾上腺素 释放, at least in the short term, then 你 会 say, "Well, shouldn't 那 主动冷暴露 also make them feel uncomfortable, like they 确实 want to get out?" Well, 那 is true at the beginning of a 主动冷暴露 方案, meaning in the 首先 周, 或 in the 秒 周 或 the third 周.

安德鲁·休伯曼：

但 what 一 finds, 和 what 你 会 find if 你 do 主动冷暴露 consistently, is 那 你 会 then become 更多 comfortable at 寒冷 temperatures away 从 the 主动冷暴露. So whereas 你 可能 have previously been the person who has 总是 寒冷 in the room 与 空气 conditioning 或 总是 seeking a sweater, 总是 wanting to bundle up, 你 会 be 更多 comfortable in 那些 寒冷 environments.

安德鲁·休伯曼：

和 the reason 对于 那 is well-substantiated 从 这 研究 和 从 animal 研究, whereby 主动冷暴露 converts 一 particular kind of fat cell, the white fat cell — which is a 非常 low metabolic output cell; it's basically a storage site 对于 能量 in the 身体 脂肪细胞 — to a 不同的 type of fat cell, which is the beige fat cell, called beige 因为 it's actually beige 或 slightly brown under the microscope, 或 even to brown 脂肪细胞, which are 非常 dark under the microscope. 和 dark 因为 they contain mitochondria 和 are 非常 metabolically 和 thermogenicly active. In other words, white fat doesn't burn many calories, it's basically a storage site, it's a bank account 对于 能量. It's filled 与 lipids, 和 那些 lipids 可以 be used if the 身体 needs 能量 和 if it goes 进入 a caloric deficit. Beige fat 和 棕色脂肪 acts as sort of a furnace, 或 the sort of fat 那 你 会 find in a candle, a fuel 那 可以 增加 核心体温.

安德鲁·休伯曼：

So beige fat 和 棕色脂肪 is 非常 good at raising 我们的 代谢 和 helps burn white fat. Now of course, it does 那 only in the context of a caloric deficit, 但 it 可以 actually help create 那 caloric deficit. Having 更多 beige fat 和 棕色脂肪 可以 增加 你的 overall core 代谢. In other words, the number of calories 那 你 burn per 天, 和 因此, the number of calories 那 你 need to either maintain 或 to lose weight. The simple translation of 这 is 那 getting 进入 寒冷 水 对于 a total of 11 分钟, perhaps 更多, 但 at least 11 分钟 per 周, divided 进入 二 或 four sessions, 可以 增加 你的 core 代谢 in part by increasing 你的 beige 和 棕色脂肪 stores. 和 我们 know how 那 works, at least in animal models. 和, there's now reason to suspect 那 the exact same mechanisms are occurring in humans.

安德鲁·休伯曼：

The primary way in which 主动冷暴露 converts white 脂肪细胞 进入 这些 更多 metabolically thermogenicly active, 代谢-increasing beige 和 brown 脂肪细胞 is 因为 去甲肾上腺素 释放了 when 我们 get 进入 the 寒冷 binds to 受体 on the surface of white 脂肪细胞 和 activates downstream 通路 such as UCP1, so 这 is an uncoupling protein 一, 那 acts on the mitochondrial 代谢 of cells 和 增加 the mitochondrial output of 那些 cells 和 the mitochondrial density of 那些 cells. In other words, it takes a cell 那 has a kind of a weak engine, 或 no engine 对于 generating 能量, 尽管 every cell has some mitochondria, it takes cells 那 have 非常 few mitochondria 和 增加 the engine size. It kind of stokes the furnace of 那些 particular cells 和 actually 可以 change gene expression in 那些 cells. So, 那's what's 确实 interesting. 主动冷暴露 causes 增加 in 去甲肾上腺素, which bind to 受体 on the surfaces of white 脂肪细胞, which triggers the 释放 of things like UCP1.

安德鲁·休伯曼：

It also causes the 释放 of things like PPAR gamma 和 cofactor PGC1. I'm going to refer 你 to a review if 你 want to learn 更多 关于 这些. 对于 那些 of 你 那 don't want to learn 更多, all 你 need to know is 那 the downstream of all 那 are 增加 in mitochondria 和 代谢. 和 actual genetic changes in the white 脂肪细胞 那 convert them 进入 beige 和 brown 脂肪细胞. 这 is 尤其是 重要 对于 adults, 因为 babies 和 young children actually don't have the ability to 发抖, 或 they have a 更少 robust capacity to 发抖. 非常 small babies 确实 可以't 发抖, so they have a lot of 棕色脂肪 in order to keep them warm. Young children eventually develop the ability to 发抖 和 maintain 这些 棕色脂肪 stores mainly 大约 the clavicles, the 心脏, the upper spine, 和 in the upper back. 和, it's no coincidence 那 kids 可以 经常 run 大约 与 a minimal of clothing 和 be comfortable in environments 那 adults 会 be 寒冷 in.

安德鲁·休伯曼：

As life goes on, 我们 tend to lose beige 和 棕色脂肪, 但 这 mechanism 那 I'm referring to points to the plasticity of white fat, meaning the ability 对于 white fat to actually convert its identity 进入 这 metabolically thermogenicly 增强 form of beige 和 棕色脂肪. So 主动冷暴露 is a terrific way to 增加 你的 core 代谢. 和 oftentimes critics 会 say, "Well, the 增加 in 代谢 isn't 那 significant," 尽管 I do want to point out again, the 93% 和 350% 增加 in 代谢 从 那 previous 研究. 但 critics then 会 say, "Well, 那 doesn't 确实 translate to 那 big of a caloric burn 期间 the 主动冷暴露." 但 to 那, 你 应该 say, "Ah, 但 那's only limiting 你的 optics to just a portion of the effects of 主动冷暴露, 因为 主动冷暴露 可以 also convert white fat to beige fat 和 棕色脂肪 和 lead to 这些 更多 lasting 增加 in 代谢.

安德鲁·休伯曼：

So 对于 any of 你 interested in increasing 你的 代谢 和/或 being comfortable in 寒冷 environments 和/或 being comfortable in terms of being able to combat 压力 mentally, 主动冷暴露, I do believe is a powerful tool. 和, there is simply no reason why 你 couldn't 和 shouldn't use the same 方案 那 I described earlier 对于 building resilience to 增加 代谢. Provided 你're hitting 那 11-分钟-per-周 threshold, 你 ought to be stimulating both mechanisms, 增加 in resilience 和 增加 in core 代谢. As I mentioned earlier, most of the detailed 研究 on the conversion of white fat to beige fat 和 棕色脂肪 通过 the use of 寒冷 have been done in animal models. 但 the human 数据 are starting to emerge. 和 if 你'd like to do the deep dive 进入 这些 mechanisms, things like UCP1, PPAR gamma, et cetera there's a beautiful review 那 was published recently in the journal Cell, which is 一 of the 三 apex journals, Nature, Science, Cell. 和 the title of 那 paper is "Adipose-组织 plasticity in health 和 disease."

安德鲁·休伯曼：

I love 这 review; it has beautiful diagrams detailing all of the 通路 从 寒冷 to 去甲肾上腺素, 通过 UCP1, downstream of things like cyclic AMP. If none of 那些 names mean anything to 你, don't worry 关于 it. 你 certainly don't need to know 这些 mechanisms to benefit 从 deliberate 寒冷-exposure 方案. If 那些 names do mean something to 你 或 你 are interested in exploring the downstream effects of 主动冷暴露 — 和 something else 那's 确实 nice 那's covered in 这 paper is how 主动冷暴露 interacts 与 fasted states 和 fed states — I think 你'll also find 这 review 非常 interesting. I don't want to go too deeply 进入 fasted states 和 fed states right now. Suffice to say 那 when 我们 are fasted, meaning when 我们 haven't eaten 对于 some period of time, 我们的 baseline 水平 of 去甲肾上腺素 和 肾上腺素 are already elevated.

安德鲁·休伯曼：

和 so, 冷暴露 at 那些 times ought to have an even greater effect on 代谢 和 resilience, 和 so on. So 对于 你 fasters 或 你的 intermittent fasters out there, if 你 确实 want to get fancy, 你 可以 do 你的 主动冷暴露 when 你 are fasted. I certainly wouldn't recommend doing it 与 a 非常 full stomach in any case. 和 as I mentioned 之前 on 这 podcast, intermittent fasting is 但 一 way, 和 certainly there are other ways, to limit total caloric intake, 对于 sake of maintaining 或 losing weight, if 那's 你的 goal. I know many 人们 are using 和 benefit 从 intermittent fasting, 然而, 和 so, it certainly 可以 be combined 与 deliberate 寒冷 exposures in order to get even greater 增加 in 去甲肾上腺素 和 肾上腺素. So 对于 那些 of 你 那 are primarily interested in using 主动冷暴露 to 增加 多巴胺 水平 in 你的 大脑和身体, 你 可以 also do a combined 方案, whereby 你 ingest caffeine 60 to 120 分钟 之前 the 主动冷暴露.

安德鲁·休伯曼：

这 is based on a 研究 那 I've talked 关于 之前, entitled "Caffeine 增加 striatal 多巴胺 D2/D3 受体 availability in the human 大脑." 和 as the title suggests, 这 研究 was done on humans, looking at the density 和/或 efficacy of 这些 多巴胺 受体 in an area of the 大脑 called the striatum, which is involved in planning 和 action 和 also suppressing planning 和 action. It's involved 非常 closely 与 whether 或 not 我们 可以 engage in behavior 和 withhold behavior, the so-called Go 和 NoGo 通路 in the 大脑. 多巴胺 plays a critical role in 那 和 many other things as well, as 你 now know. So, why 会 你 want to ingest caffeine 60 to 120 分钟 之前 主动冷暴露? Well, as I talked 关于 earlier, 多巴胺 可以 增加 quite substantially in response to 主动冷暴露, 但 多巴胺 on its own doesn't do anything; it has to bind to 受体.

安德鲁·休伯曼：

和 这 paper shows quite definitively 那 ingesting caffeine, in 这 case it was a 300-milligram dose of caffeine, which is 关于 the dose of caffeine in 二 或 三 cups of coffee — it depends on the 力量 of the coffee of course, 但 it's not an outrageous amount of caffeine. 那 增加 the density 和/或 efficacy of 这些 受体, which 会 allow 那 多巴胺 to have its greatest effect. 和 对于 那些 of 你 那 want to get 确实, 确实 fancy, I suppose 你 could do 这 fasted, so 你 get the further 增加 in 去甲肾上腺素, then 你 get the 多巴胺 增加 从 the 冷暴露, the [inaudible 01:23:05], the 多巴胺. 尽管, I do want to point out 那 at some point, 你 start layering together enough 方案 那 你 会 be spending 你的 entire 天 trying to get 这 多巴胺 pulse, 和 I 会 hope 那 你 会 have other activities 那 你 会 engage in.

安德鲁·休伯曼：

但 if 你're getting up in the 早晨 和 你're fasted 因为 你 haven't eaten all 夜间, 和 你 have a cup of coffee, 和 then 60 分钟 later, 你'd take 你的 冷水淋浴 或 二 小时 later, 你'd do 你的 寒冷 immersion 或 你的 冷水淋浴, 你 会 be layering together 这些 不同的 mechanisms of 多巴胺 受体, 肾上腺素, 和 so forth, in a way 那 at least to me doesn't seem incompatible 与 having some other life, like going to school 和 having relationships, et cetera. 和 这 增加 in 多巴胺, particularly in the striatum, is not a trivial 一. I do want to point out, as the authors do, 那 preclinical 研究 have shown 那 增加 in striatal 多巴胺 induced by things like modafinil, which is used to treat ADHD 和 treat narcolepsy, is necessary 对于 their wake-promoting actions. What 这 确实 says is 那 just having elevated 水平 of 多巴胺 从 a drug 或 从 an ice bath, 或 what have 你, is not sufficient to get the effects of 多巴胺.

安德鲁·休伯曼：

你 确实 need the 受体 to be available, 和 你 need 那些 受体 to be available in the appropriate density, 和 你 need 那些 受体 to be available in the appropriate density, in the striatum, in particular. So I think there are a number of reasons why if it's compatible 与 the other aspects of 你的 health, 因为 of course 总是 你 have to consider 这 on a background of cardiovascular health 和 血液 pressure, et cetera, 那 ingesting a cup 或 二 of coffee an 小时 之前 你的 ice bath, maybe fasted as well, could be quite beneficial 对于 increasing 多巴胺 over quite extended periods of time. A couple of key points 那 你'll want to pay 注意力 to in thinking 关于 主动冷暴露 和 代谢. In the Søberg 研究, they also explored the use of sauna 和 how to use sauna, meaning deliberate 热 in conjunction 与 寒冷.

安德鲁·休伯曼：

我们 are going to do an entire episode 关于 the use of 热 对于 健康与表现, so 那 is not the 专注 now. 然而, it does raise an 重要 point 那 我们 do need to address at 这 moment, which is if 你 are using sauna, 或 if 你 are taking warm showers, 或 if 你 are simply using 主动冷暴露 of any kind, 应该 你 get 进入 the 热 afterward 或 之前 或 not at all? 和 这 is where 我们 可以 point to the so-called Søberg principle, at least I call it the Søberg principal. The Søberg principal, named 之后 首先 author of 这 研究 I referred to earlier, Dr. Susanna Søberg. In science, it is appropriate to take a key piece of 数据 和 call it a principle if, in fact, it translates to something larger, which I believe it does. It is generally not appropriate 对于 人们 to name a principle 之后 themselves, 尽管 there are a few scientists 那 have done 那.

安德鲁·休伯曼：

So I have named it the Søberg principle, 但 I did 那 to give it appropriate credit to Dr. Susanna Søberg, who discovered 那 和 pointed out quite appropriately, 那 to achieve the greatest 增加 in 代谢 通过 主动冷暴露, 你 want to force yourself to reheat on 你的 own 之后 the 主动冷暴露. Meaning 你 wouldn't want to go 从 the 冷水淋浴 to a hot shower, 或 从 the 冷水淋浴 to a sauna. Rather, if 你 were going to start 与 a hot shower 或 你're going to start 与 a sauna, 那 你 会 end 与 the 寒冷, 和 then 你 会 reheat naturally. Now, I personally take a 冷水淋浴 a few times a 周 或 do 寒冷 immersion. 和 因为 I'm not specifically focused on increasing 代谢, 尽管 I probably 应该 be, 那's not what I'm using it 对于 now. I 会 take a hot shower afterwards. 和 in doing so, I'm short-circuiting some of the further metabolic 增加 那 I 会 achieve were I to just end 与 the 寒冷.

安德鲁·休伯曼：

So the Søberg principle is if 你 want to 增加 你的 代谢, end 与 寒冷. 和 我们 可以 take 这 a step further 和 say 那 if 你 want to use 主动冷暴露 to 增加 代谢, 那 你 应该 make sure 那 你 get to the point where 你 发抖. 和 the reason 对于 这 is 那 there are a series of 研究, 但 in particular 一 研究 published in the journal Nature, excellent journal, in the year 2018, showing 那 主动冷暴露 那 evokes 发抖 从 the 肌肉 causes the 释放 of a molecule called succinate 从 the 肌肉. 和 那 succinate plays a key role in activating brown-fat thermogenesis, which 你 now have heard 关于 和 understand as critical to the 增加 in 代谢 caused by 主动冷暴露. So what 这 means is if 你 want to 增加 你的 代谢, end on 寒冷, 那's the Søberg principle, 和 as best 你 可以 try 和 get to the point where 你 are 发抖, either when 你 are in the 冷暴露 或 immediately afterwards.

安德鲁·休伯曼：

Now, 一 efficient way to do 这 is to, 对于 instance, 你 could get 进入 the 冷水淋浴 对于 a 分钟 或 二 分钟 或 三 分钟, uncomfortably 寒冷, 但 safe to stay in. Remember, 那's 我们的 general rule of thumb. Then turn off the 水 和 stand there. Make sure 那 你're not holding yourself close to 你的 身体, 你're not hugging yourself to try 和 keep yourself warm, 但 rather 你的 limbs are extended at 你的 sides. 和 then if 那 fails to induce 发抖, then to turn on the 寒冷 水 again, 和 then turn it off again. So alternating, perhaps, a 分钟 to 三 分钟 of 冷暴露, followed by a 分钟 to 三 分钟 of drying out in 空气 和 going back 进入 the 冷暴露, et cetera.

安德鲁·休伯曼：

I 可以 tell 你 这 从 experience, 这 is a pretty brutal 方案. If 你 have 从不 tried getting 进入 an ice bath, 或 寒冷-水 immersion 或 冷水淋浴 对于 一 分钟 和 then getting out 和 trying to stand there 与 你的 arms extended in cool 或 寒冷 空气 对于 一 分钟 和 then getting back 进入 the 冷水淋浴 或 水 immersion, 你 are in 对于 an experience. 因为 even 对于 那些 of 你 那 are pretty 发抖 resistant, 你'll find 那 it is much, much harder to get out of 那 寒冷 水 和 stand there arms extended 和 drying off by evaporation, which further draws 热 从 the 身体, than it is to wrap yourself in a towel, get in a warm shower 或 a sauna. So there's certainly no requirement to end on 寒冷, there's certainly no requirement to induce 发抖.

安德鲁·休伯曼：

但 if 你的 primary goal is to induce 增加 in 代谢, both in the short term 和 in the long term, following the 冷暴露, well then, 你'll want to end on 寒冷, 和 你'll want to find a way to 发抖, provided 那 the 水平 of 寒冷 那 你're exposing yourself to is still safe 对于 你 overall. So up until now, I've been talking 关于 主动冷暴露 as a potent stimulus 对于 the 释放 of 去甲肾上腺素 in the 大脑和身体, 和 indeed it is.

安德鲁·休伯曼：

但 the way I've been describing it has been in the context of circulating plasma 水平 of 去甲肾上腺素, meaning circulating within the 血液. What I haven't mentioned, 但 is absolutely true, is 那 the 脂肪细胞 themselves actually receive input 从 neurons. So there are neurons 那 释放 去甲肾上腺素 in response to 寒冷 directly 进入 the fat. So I want to give 你 这 picture of how the architecture of all 这 works, 因为 I think it 可以 help 你 navigate 和, indeed, build better deliberate 寒冷-exposure 方案. 你的 adrenal glands 释放 去甲肾上腺素 和 肾上腺素. 你的 大脑 has sites within it, like the locus coeruleus, 那 释放 去甲肾上腺素 和 肾上腺素. 但 there are also neurons within 你的 皮肤 那 sense 寒冷 和 other neurons 那 可以 directly 释放 去甲肾上腺素 进入 the fat stores 和 cause 那些 white 脂肪细胞 to convert to beige 和 棕色脂肪.

安德鲁·休伯曼：

和 I think 这 particular aspect of 我们的 physiology is 经常 overlooked in 研究. 和 when 人们 say, "Oh well, the 增加 in 代谢 aren't 那 great, the circulating 水平 of 去甲肾上腺素, 那些 are 非常 large, 但 they're 非常 transient," 和 so on, 那 fails to understand 那 neurons 那 actually sense 寒冷 are in a position to communicate via other neurons directly to the 脂肪细胞 和 释放 去甲肾上腺素 进入 那些 脂肪细胞, which as I pointed out earlier, set off a huge set of immediate 和 long-term cascades of even gene expression changes. So the picture 那 I'd like 你 to have in 你的 心智 is 那 when 你 get 进入 the 寒冷, yes, of course, 你 experience 那 as an experience of "I don't want to do 这, I'm going to overcome 这, I'm going to climb over 这些 mental walls 那 represent 肾上腺素 释放 in my 大脑和身体," 但 also 那 你的 脂肪细胞 are receiving signals, 去甲肾上腺素 signals 那 are changing 那些 脂肪细胞 in the way 那 they metabolize 能量.

安德鲁·休伯曼：

Now, I'd like to shift 我们的 注意力 to the use of 主动冷暴露 对于 sake of 身体表现. 和 there are a lot of opinions out there 关于 the use of deliberate 寒冷, whether 或 not it 应该 be done, 对于 instance, 之前 或 之后 运动, whether 或 not if done immediately 之后 力量 训练 或 hypertrophy 训练, meaning 训练 designed to grow 肌肉 或 make them stronger, whether 或 not it 可以 inhibit 那 process, 和 so on 和 so forth. I think today in looking over the literature 和 trying to bring forward the simplest 和 most straightforward 和 yet scientifically grounded 方案, 我们 可以 set up some general guidelines 那 会 allow most, if not all of 你, to still extract the benefits of 主动冷暴露 on 身体表现, 没有 getting too neurotic 关于 the exact timing.

安德鲁·休伯曼：

但 对于 sake of discussion 和 因为 it's a prominent theme in many online communities, let's just start 与 the big 一 out there, meaning the question of whether 或 not doing an ice bath 或 doing 主动冷暴露 或 taking a 冷水淋浴 之后 力量/hypertrophy 训练, meaning 训练 designed to 增加 力量 或, 和/或 I 应该 say, the size of 肌肉 会 somehow short-回路 或 diminish 那 process, whether 或 not it 会 减少 或 eliminate 那些 力量 gains 和 hypertrophy gains. 和 the short answer 那 I was able to arrive at on the basis of a review article 那 I'll talk 关于 in a moment, 和 some other 研究 as well, is 那 if 你的 main goal is hypertrophy 和 力量, it is probably best to avoid 寒冷-水 immersion 和 ice-bath immersion in the four 小时 immediately following 那 力量 和/或 hypertrophy 训练.

安德鲁·休伯曼：

Again, if 你的 main goal is to achieve hypertrophy 或 力量 或 some combination of 那些, probably best to avoid 寒冷-水 immersion up to the neck 或 ice-bath immersion up to the neck immediately 之后 力量 和 hypertrophy 训练 和 extending out to 关于 four 小时 之后 那 训练. If 你're 确实 neurotic 关于 这, then perhaps 你'd want to move the 寒冷-水 exposure to a 不同的 天 entirely, 但 it all depends on how neurotically attached 你 are to getting every last bit of 力量 和 hypertrophy. 和 if 那's 你的 goal, terrific.

安德鲁·休伯曼：

Well then, probably moving the 冷暴露 four 小时 或 更多 away 从 那 训练 is going to be necessary 对于 你. Now, 你'll notice I did not talk 关于 冷水淋浴, 和 the reason I did not talk 关于 冷水淋浴 is 那 there simply are not 非常 many 研究 of 主动冷暴露 通过 冷水淋浴, 对于 the reasons I talked 关于 at the beginning of the episode. It's hard 对于 me to imagine 那 taking a brief 冷水淋浴 之后 a 力量 或 hypertrophy 训练 session 会 completely reverse 或 short-回路 the effects of 那 力量 和 hypertrophy 训练. 但 again, if 你're neurotically attached to getting every last bit of 力量 和 hypertrophy out of 你的 训练 sessions, then by all means, err on the side of caution 和 wait four 小时 或 更多 to do 你的 冷水淋浴, just as 你 会 wait four 小时 或 更多 to do 你的 寒冷-水 immersion.

安德鲁·休伯曼：

Now, there are nice 数据 pointing to the fact 那 doing 寒冷-水 immersion 之后 a hard run, so 耐力 训练, 或 even sprint 和 interval 训练, 或 之后 a weight workout, where 你的 main 专注 is on 表现 of 那些 movements, 或 之后 a skill 训练 workout, where 你的 main 专注 is on 表现 of 那些 movements, 那 there's no reason to think 那 那 寒冷-水 immersion, 或 ice bath, 或 冷水淋浴 会 inhibit the progress 或 the stimulus 那 会 lead to progress 那 occurred 期间 那 训练 session. In other words, I don't see any reason based on the literature to avoid 主动冷暴露 immediately 之后 训练. Again, unless 你的 goal is hypertrophy 和 力量. 和 in fact, there's a 非常 nice review 那 was recently published on 主动冷暴露 和 how it 可以 impact 身体表现, whether 或 not it's done 之前 或 之后 不同的 types of 训练. 和 so forth.

安德鲁·休伯曼：

The paper is entitled "Impact of 寒冷-水 immersion compared 与 passive 恢复 following a single bout of strenuous 运动 on athletic 表现 in physically active 参与者: A systematic review 与 meta-analysis 和 meta-regression." So 这 is a meta-analysis of 52 研究 那 looked at a tremendous number of variables 和 context, as 你 会 expect in a meta-analysis of 52 研究. I'm going to read 你 the conclusions of the 研究, 和 I 会 provide a link. 我们 certainly don't have the time to go 通过 all the details of the 研究. I 会 highlight a few 具体的 outcomes 那 I found particularly interesting, 但 here I am paraphrasing their conclusions 那 寒冷-水 immersion — I want to emphasize immersion, not 冷水淋浴, 但 寒冷-水 immersion — they say was an effective 恢复 tool 之后 high-intensity 运动. They observed positive outcomes, meaning improvements in certain variables, 对于 muscular power, muscular soreness — meaning reduced muscular soreness, 增加了 muscular power — perceived 恢复 之后 24 小时 of 运动.

安德鲁·休伯曼：

然而, there were certain forms of 运动 那 were not benefited by 寒冷-水 immersion, such as eccentric 运动, 运动 focusing only on the lowering component, 或 the so-called eccentric component of resistance 运动. They saw some 非常 interesting dose-response relationships 对于 things like 耐力 训练 — meaning the longer the 冷暴露, post 耐力 训练, the 更多 improvement in 耐力 表现 — reductions in circulating creatine kinases 和 things 那 relate to 肌肉 damage under certain conditions. At some point in the future, by the way, 我们'll do an entire episode on creatine 和 creatine kinases, which are 重要 not just 对于 muscular function, 但 also 对于 大脑 function. 但 the basic takeaway was 那 寒冷-水 immersion performed 之后 high-intensity 运动 was beneficial 从 a number of 不同的 standpoints 和 indicated 那 shorter-duration 冷暴露 和 lower temperatures 可以 改善 the efficacy of 寒冷-水 exposure if used 之后 high-intensity 运动. Okay. There, I'm directly pulling 从 their conclusions.

安德鲁·休伯曼：

So what 这 says is 那 it's not just 那些 longer-duration 30-, 45-分钟 和 60-分钟 方案 of 寒冷-水 immersion 那 我们 discussed earlier, 但 also shorter-duration 一-分钟, 三-分钟, five-分钟 exposures to lower temperatures — temperatures 那 会 make 你 psychologically want to get out as soon as 你 possibly 可以, 但 again, 那 你 可以 safely stay in — done 之后 训练, 确实 have been shown to 改善 outcomes in terms of 减少 soreness 和 improving 训练 efficacy. Meaning 你的 ability to get back 进入 训练 更多 quickly 和 thereby deliver 更多 训练 stimuli to a given 肌肉 或 in 你的 耐力-训练 方案. Translate to English, what 这 means is 那 taking a 冷水淋浴 或 getting 进入 an ice bath 或 some other form of 寒冷-水 immersion within the immediate...

第2部分（共3部分）结束 [01:06:04]

安德鲁·休伯曼：

... do an ice bath 或 some other form of 寒冷-水 immersion within the immediate 分钟 或 even the immediate 小时 following 你的 训练 has been shown to be beneficial. I'm sure a number of 你 have questions. 对于 instance, "How long 应该 你 be in 那 冷暴露? Is it the same as the 11-分钟 threshold described earlier?" To be honest 与 你, there are not enough 研究 to 确实 point to the critical threshold 对于 eliminating 或 减少 delayed-onset 肌肉 soreness 或 对于 getting maximal 结果 从 power 和 耐力 训练. 但 这 研究 does make a couple of key points, 和 here I 会 just paraphrase, 对于 instance, 那 寒冷-水 immersion is 更多 可能 to positively influence muscular power 表现, to 减少 肌肉 soreness, to 减少 serum creatine kinase, 和 to 改善 perceived 恢复 之后 high-intensity 运动, as compared 与 passive 恢复. 这 可以 be translated to 寒冷-水 exposure 之后 训练 is beneficial 和 probably better than passive 恢复 从 a number of standpoints.

安德鲁·休伯曼：

In addition, they say 那 dose-response relationships, meaning the amount 和 the degree of 寒冷 那 人们 were exposed to 和 how 经常 they did 那, in particular in lower-温度 寒冷-immersion — so 这些 会 be the sorts of 寒冷-immersion 方案 那 are 一 分钟 或 二 分钟, 三 分钟, maybe five 分钟, 但 那 一 couldn't stay in there longer 因为 it feels stressful 和 一 wants to get out — may be 更多 effective 之后 high-intensity 运动 对于 removal of serum creatine kinase. As well, 那 这些 shorter-duration 寒冷-水 immersion approaches may be 更多 effective 之后 high-intensity 耐力 表现 as well. So all of 这 可以 be translated to say 那 unless 你的 main goal is hypertrophy 和 力量, 那 冷暴露 — ideally 寒冷 immersion 和 寒冷 水, ice bath, 但 if 你 don't have access to 那, then 冷水淋浴 — is 可能 going to be beneficial if done immediately 之后 或 in the 分钟 或 小时 之后 你的 训练, 尤其是 high-intensity 训练.

安德鲁·休伯曼：

一 particularly nice thing 关于 这 meta-analysis is 那 it included some 研究 那 involve the use of cooling packs. So again, vests 那 可以 hold 本质上 ice packs, 和, indeed, even cryotherapy chambers, 和 so on. There's a nice table in the 研究 if 你 want to get 确实 detailed 和 go 和 look specifically at 那些 研究, I invite 你 to do 那. 我们'll put a link to 这 研究 in the caption 对于 这 episode. 但 all in all, what 这 研究 shows is 那 主动冷暴露 可以 be 非常 useful 对于 恢复, 可能 通过 reductions in 炎症 in 肌肉 和 connective 组织.

安德鲁·休伯曼：

和 while 这 研究 did not look specifically at the mechanisms of reduced 炎症 caused by 主动冷暴露, 那些 mechanisms are somewhat known. There are a number of 研究 那 have pointed to the fact 那 deliberate 寒冷, 和 寒冷 generally, 可以 减少 炎症性的 cytokines such as IL-6, interleukin six. It 可以 增加 anti-炎症性的 cytokines such as interleukin 10, 和 so on.

安德鲁·休伯曼：

没有 getting 进入 all 那些 details, I think it's sufficient to say 那 if 你 are somebody who experiences a lot of delayed-onset 肌肉 soreness, taking a 冷水淋浴 之后 你的 训练 或 getting 进入 a 寒冷 immersion 之后 你的 训练, even if it's a few 小时 later, ought to help. 和 if 你 are doing particularly intense 训练, then 你 probably want to ratchet up the number of 冷暴露 sessions 那 你're doing, even if 那些 have to be done on separate 天 从 你的 训练, 因为 a lot of the 炎症性的 effects of 训练, 耐力 和 力量 训练, are actually occurring some 小时 away 从 the 训练 stimulus. So it's not just 那 炎症 goes up radically 期间 训练, which it 经常 可以, 但 那 it 可以 occur even in the 天 和 even 周 afterwards, depending on how intense 和 how long duration 那 训练 is. So 主动冷暴露 is 非常 powerful as an anti-炎症性的 tool.

安德鲁·休伯曼：

Now, I'd like to emphasize the topic 那 我们 touched on at the beginning of the episode, which are 那些 无毛皮肤 surfaces, the hands, the upper face, 和 the bottoms of the feet, 通过 which 热 is 尤其是 good at leaving the 身体. 和 another way of putting 那 is 那 一 可以 cool the 身体 much 更多 efficiently 通过 the 无毛皮肤 surfaces. Now, if 你 want to understand all of the science behind 这 和 all of the various applications, I invite 你 to please listen to the episode 那 I did 与 Dr. Craig Heller, again, in the Biology Department at Stanford. 对于 sake of 这 episode, I'm just going to detail a couple of findings 从 his laboratory. The 首先 一, dealing 与 运动-induced hyperthermia, 因为 I think 这 is 非常 interesting, 和 it 可以 even save lives if 你 understand the way 这 works.

安德鲁·休伯曼：

There's a particular paper 那 focuses on 这, 和 我们 会 put a link to 这 as well. The title of 这 paper is "Novel application of chemical 寒冷 packs 对于 treatment of 运动-induced hyperthermia: A randomized controlled trial." 这 is a pretty brutal 研究 — brutal 对于 the 受试者, 那 is. What the 研究 involved was having 受试者 walk on a treadmill at a pretty significant incline, anywhere 从 9-17%, wearing a substantial amount of clothing 那 was not well ventilated, 和 the room was kept to 40 degrees Celsius, which is 104 degrees Fahrenheit. 这 is definitely not something to do at home. 这 研究 was designed to induce hyperthermia, which as I mentioned earlier, 可以 be quite dangerous. 和 they compared 二 types of cooling.

安德鲁·休伯曼：

In the 首先 form of cooling, 那 they call traditional cooling, they had ice packs on their neck, in their armpits 和 in their groin. 和 in the other group, there was the so-called glabrous-皮肤 cooling. So the 手掌, the 脚底 of the feet, which were actually — so they were cooling inside the boots, 或 inside of gloves — 和 on the upper portion of the face. 和 the basic takeaway of 这 研究 is 那 by cooling the 无毛皮肤, the 受试者 were able to sustain walking on 这些 incline treadmills 对于 much longer than were the 人们 who received traditional cooling. 和 also, the return to baseline 温度 was much faster in the 无毛皮肤-cooling group.

安德鲁·休伯曼：

So how 这 translates to the real world is 那 if ever 你 are hyperthermic, 或 someone else's hyperthermic, 一 way to cool them down quickly is to cool 这些 手掌的 glabrous, 脚底 of the feet glabrous 和 upper portion of the face glabrous portions of the 身体, using cool rags, using ice packs, 或 using any number of 不同的 寒冷 objects 或 temperatures.

安德鲁·休伯曼：

一 key thing, if 你're going to use 无毛皮肤 cooling, is 那 whatever 你 use to cool 那些 surfaces cannot be so 寒冷 那 it causes vasoconstriction. 因为 as I mentioned earlier, the arterio-venous astomoses, 这些 portals of arteries directly to veins 那 exist only in 这些 无毛皮肤 surfaces, the way 那 they're able to cool the 身体 和 本质上 pass cool 进入 the 身体 — 尽管 那's not 确实 what they're doing, they're actually extracting 热 从 the 身体 to be technical; they're extracting 热 从 the 身体. The only way they 可以 do 那 is if 那些 veins don't collapse, 和 veins 会 collapse if they are made 非常, 非常 寒冷. So if 你 want to use 无毛皮肤 cooling to offset hyperthermia, 或 对于 the other forms of 表现 which 我们'll talk 关于 in a moment, 你 need to use a cool object 或 surface 那 is not so 寒冷 那 it causes vasoconstriction.

安德鲁·休伯曼：

和 这 可以 be a little bit tough to dial in, meaning it 可以 be tough to identify such an object. 和 对于 那 reason, Dr. Heller 和 some of his colleagues have developed a commercial product called the CoolMitt. 你 可以 actually go to their website, coolmitt.com. I don't have any financial 或 other relationship to them. I know they've been developing 这 technology 对于 some period of time. It involves a glove 那 你 put 你的 hand 进入, it circulates 水 of a given 温度, 和 it does so at a 温度 那 is sure to not cause vasoconstriction of the palm. 和 你 may be asking, "How 可以 你 just put 你的 hand 进入 一 glove 和 have 这 work?" Well, 那's how powerful 这些 无毛皮肤 surfaces are. Even just by cooling 一 palm, the 核心体温 drops radically.

安德鲁·休伯曼：

Now, 那's their commercial technology. I know 那 some 人们 out there have started to experiment 与 a home version of 这, which 会 be taking a package, 对于 instance, of frozen blueberries, 或 some other 寒冷 drink, 或 寒冷 metal object, 和 actually bringing it 进入 the gym 或 out on a run. There are even 人们 who are now developing cooled bicycle handles 对于 long rides. 这 可能 seem a little kooky 或 crazy to 你, 但 as 你'll soon hear in the 研究 I'm 关于 to describe, the 增加 in 耐力 和 in the volume of 力量 训练 那 人们 可以 conduct if they appropriately cool their 身体 通过 这些 无毛皮肤 portals is actually quite significant.

安德鲁·休伯曼：

So again, as it relates to hyperthermia, if someone is overheating, by all means try 和 get them out of 那 热. Get them to stop exercising. 你 可以 die 从 hyperthermia. Try 和 cool the bottoms of the feet, the 手掌 of their hands, 和 the upper portion of their face. 那 does not mean 那 it 会 be a bad idea to put 寒冷 水 on the top of their head. 那 probably 会 also help. 和 perhaps on their neck. What is probably not going to be a good idea is to do the 更多 standard thing of draping someone in 寒冷 towels on the surface of their 身体, 因为 as I mentioned in the beginning of the episode, 那 thermostat in the hypothalamus, the medial preoptic area, 会 通常 react to 那 by increasing 核心体温 further.

安德鲁·休伯曼：

The effects of 无毛皮肤 cooling on 身体表现 are truly remarkable, provided the 无毛皮肤 cooling is done correctly. 和 I want to point out 那 the main degree of effect is on volume, 或 the ability to do 更多 work. 和 I want to point 这 out 因为 I think 那 many 人们, certainly in the 运动 science community, 但 even in the general public, when they hear 关于 some of 这些 effects 那 are measured in the laboratory, they sort of look at 那些 effects a bit askance, 和 they think, "Well, 那's not 可能, right?" Effects, 对于 instance, 那 have been documented showing doubling 或 tripling of the number of dips 那 一 可以 do in a relatively short amount of time. 或 doubling of the number of pull-ups 一 可以 do, 或 14% 增加 in 力量, 或 even comparable degrees in 增加 in weight 训练 output to 人们 who are on 表现-增强, drugs, et cetera, et cetera.

安德鲁·休伯曼：

Part of the confusion is 那 the effects of proper 手掌的 cooling, 因为 it almost 总是 is done by 手掌的 cooling 和 更少 经常 in 这些 experiments by cooling of the bottoms of the feet 和 the upper portion of the face, 但 那些 effects tend to be the ability to do 更多 work over time. 和 just to illustrate some of the major effects 那 the Heller Lab has seen 和 那 are documented in 这 manuscript 那 I'll share 与 你 in a moment, the typical 方案 is to have 人们 come in 和 do some 耐力 训练, so running on a treadmill, 和 to have a condition where 一 group is actually doing 手掌的 cooling while they are on a bike 或 on a treadmill, 和 inevitably the outcome is 那 they 可以 do 更多 work. They 可以 pedal further at a given speed, 或 they 可以 run longer at a given speed than 人们 who are not doing 手掌的 cooling 或 who are receiving cooling by way of 寒冷 compress to the back of the neck 或 ice pack to the armpits, et cetera.

安德鲁·休伯曼：

So the effects of 手掌的 cooling are 非常 clear 和 非常 robust, 和 in the context of 耐力 运动, almost 总是 allow 人们 to do 更多 work, to go longer 与 更少 perceived effort, 和 to quit later, so to speak. In terms of 力量 训练, they've looked at the capacity to perform sets of dips. So 一 of the 更多 famous examples of 这 那 Dr. Heller shares in the episode 那 我们 did earlier, 和 那 你 可以 find at hubermanlab.com, involves someone coming in 和 doing sets of dips, maybe 40 dips. 这 person actually could do 40 dips on their 首先 set. Then, resting 对于 a period of 二 to 三 分钟, 和 then doing 35, 和 then resting 对于 a period of 二 或 三 分钟, 和 then doing progressively fewer 和 fewer 和 fewer to the point where over a period of time, they add up the total number of dips 那 they 可以 do, 和 then they have them come back 之后 a period of 恢复. So not immediately 之后, 但 take a couple of 天, come back 和 do effectively the same 方案, 但 期间 their rest periods, they're doing 二 分钟 of 手掌的 cooling, which 本质上 allows 热 to move out of the 身体, lowering 核心体温, in other words.

安德鲁·休伯曼：

和 what they find is 那 they see enormous 增加 in the total number of dips 那 人们 可以 do. 但 那 doesn't mean 那 the person goes 从 being able to do 40 dips to being able to do 50 dips 或 60 dips on 那 首先 set. What it means is 那 they are able to do 40 on the 首先 set, then 40 on the 秒, then 38 on the third, 和 so on 和 so forth, so 那 the total duration of the workout is extended, 和 yet they're doing much 更多 work, even though it takes 更多 time. So 那's an 重要 point, 和 I think a point 那 perhaps wasn't as clear 或 as clearly made by me in the previous episodes 那 discussed 这 topic.

安德鲁·休伯曼：

对于 那些 of 你 那 are interested in exploring 手掌的 cooling, 首先 of all, I recommend taking a brief glance 或 even a deep dive 进入 这 研究, which is entitled "Work volume 和 力量 训练 responses to resistive 运动 改善 与 periodic 热 extraction 从 the palm." In 这 研究, they describe big 增加 in anaerobic — meaning 力量 训练 — output, things like improvement in dips, improvement in bench press, improvement in pull-ups, et cetera in human 受试者. 和 it's a 确实 nice 研究 和 points to some of the 方案 那 你 可能 be able to adapt in 你的 own setup. 对于 instance, over six 周 of pull-up 训练, palm cooling in between sets 改善了 volume by 144%, 和 这 was in experienced 受试者. So 那's interesting, 因为 a lot of 研究 of 力量 训练 和 improvements in hypertrophy 和 力量 are done in inexperienced, untrained athletes, which changes the picture somewhat compared to experienced athletes.

安德鲁·休伯曼：

They found 那 力量, meaning the 一-repetition maximum, 增加了 22% over 10 周 in bench-press 训练. 和 they point to the particularly strong effects of using 手掌的 cooling when 人们 reach plateaus in 耐力 和 力量 训练. 和 there, I think it's an 重要 point. I think 那 if 你're going to explore 手掌的 cooling, it's probably not the sort of thing 那 你're going to do in every run 或 in every bout of cycling 或 in every 力量-训练 session, 但 那 it 可能 be used to vastly 增加 你的 volume 或 vastly 增加 你的 耐力 in a given session, 或 a set of sessions, in order to push 通过 plateaus.

安德鲁·休伯曼：

A particularly interesting point in light of 那 is Dr. Heller has observed again 和 again 那 手掌的 cooling 减少 delayed-onset 肌肉 soreness 或 可以 eliminate it entirely. 和 那's 非常 interesting 因为 it also points to the fact 那 减少 核心体温 may somehow be involved in short-circuiting the normal mechanisms of delayed-onset 肌肉 soreness. 和 你 可能 say, "Well, how 会 温度 be involved in delayed-onset 肌肉 soreness?"

安德鲁·休伯曼：

Well, I want to refer 你 back to the meta-analysis 那 我们 talked 关于 earlier where the short-duration, 非常 寒冷 温度 exposure 之后 训练 did indeed 减少 delayed-onset 肌肉 soreness, in part 通过 reduction in creatine kinase. So it's not inconceivable 那 温度 和 delayed-onset 肌肉 soreness are related. 和 那 raises perhaps the most 重要 point, which is the way 那 手掌的 cooling 可以 改善 表现 by way of 减少 核心体温 is known.

安德鲁·休伯曼：

和 那 is 因为 when 一 engages in 运动 或 muscular output of any kind, 力量 或 耐力 运动, the range of temperatures under which a 肌肉 可以 perform is actually 非常 narrow. There's an enzyme called pyruvate kinase, which is critical to 肌肉 contractions. 和 pyruvate kinase 可以 only function in a 非常 narrow range of temperatures. If 那 温度 gets too hot, meaning if the 肌肉 heats up locally, whether 或 not by running 或 cycling 或 swimming 或 weight lifting, the ability 对于 那 肌肉 to continue to contract is reduced 和 eventually is short-circuited completely. 和 I think 这 is a much under-explored, 或 at least a much under-discussed, aspect of so-called muscular failure 或 the failure of 一 to continue to endure in running. So 对于 instance, when 你 run, as compared to a bench press 或 something, 你 don't stop running 因为 你 可以't actually contract the 肌肉 further, 但 somehow signals 关于 the heating up of muscular 组织 are conveyed to the 大脑, there's a crosstalk there, it's probably bidirectional, 和 人们 stop. They quit, right? 这 is the quitting reflex.

安德鲁·休伯曼：

In 力量 训练, 一 可以 no longer perform a repetition 或 set of repetitions in part 因为 of heating up of the 肌肉 locally. There are other mechanisms as well, of course, 和 I realize 那. 但 what's 非常 clear 从 the 手掌的 cooling work is 那 by simply holding onto a cool object ... remember, not an object so 寒冷 那 it constricts the vessels of the 手掌 或 constricts the vessels on the bottoms of the feet. 但 by holding onto a relatively cool object in 一 或 both hands in between sets 对于 二 分钟 或 so, 你 可以 非常 efficiently 减少 你的 核心体温. 和 in doing so, 减少 the 温度 of the 肌肉 那 are doing the work, 增加 the capacity 对于 pyruvate kinase to continue to allow 你的 肌肉 to contract, 和 thereby allow 你 to do 更多 volume of 耐力 和 力量 训练.

安德鲁·休伯曼：

So a simple 方案 那 Dr. Heller passed to me is find a relatively cool object. So 你 could, 对于 instance, fill 二 bottles 与 寒冷 水, maybe put a few ice cubes in there, right? 这 is not exact, 因为 我们're not talking 关于 the commercial CoolMitt product here, 我们're talking 关于 an at-home version. 或, use a pack of frozen blueberries 或 broccoli, a pack of 那些, as what he described. 和 then in between sets to put 你的 hands, 和 ideally 你'd put the bottoms of 你的 feet, 但 那's not 总是 feasible in most gyms where they won't let 你 take off 你的 shoes 和 so forth. 但 to put the 手掌 of 你的 hands on 那 cool surface 对于 a 分钟 或 二 分钟 between sets 和 then returning to 你的 sets of work.

安德鲁·休伯曼：

Now, if 你 are heating up 通过 other mechanisms like 你're wearing a stocking cap, 和 你're in a 非常 warm environment, 这 可能 not have as potent of an effect as if 你 were to do 这 cooling in a 更多 moderate environment, wearing lighter clothing, et cetera.

安德鲁·休伯曼：

So by all means, warm up to do 你的 运动, lubricate 你的 joints, 和 get 进入 a place where 你're not going to injure yourself doing whatever form of 运动 你 do. 但 then if 你'd like to explore 手掌的 cooling — I know a number of 人们 who have written to me saying they heard 关于 手掌的 cooling on the episode 与 Dr. Heller, they've tried 这 和 they see quite excellent 结果. It does take some discipline. It's 一 thing to just hang out in the gym 和 play on 你的 phone in between sets. It's another to do deliberate cooling 与 你的 手掌, 或 the bottom is 你的 feet, 或 the upper portion of 你的 face. 你 可能 get some weird looks, 但 of course, 你'll be the 一 doing significantly 更多 volume, not experiencing delayed-onset 肌肉 soreness, 和 achieving better 耐力 和 力量 gains, were 你 to do 这 properly.

安德鲁·休伯曼：

Now, as a final topic related to the use of 主动冷暴露 对于 improving 健康与表现, I'd like to touch on 这 theme 那 exists online, on social media, on YouTube, 和 in various fitness communities, of using 主动冷暴露 to the groin, in particular to the testicles, in order to try 和 增加 testosterone. 和 while 这 可能 sound 确实 kooky, indeed, 这 practice exists. Indeed, if 你 were to go onto Amazon, there are actually ice-pack underwear 那 are being marketed 对于 sake of increasing testosterone.

安德鲁·休伯曼：

Now, I am not aware of any 具体的 well-controlled 研究 那 show 那 这 indeed works. I 可以 imagine, based on what I know 关于 the 神经系统, testosterone 和 寒冷, et cetera 那 there are a couple of mechanisms by which 一 可能 experience 增加 in testosterone as a consequence of 主动冷暴露.

安德鲁·休伯曼：

首先 off, let me say, there is no reason why 你 会 have to apply 这些 ice packs in the way 那 I just described. 一 could, of course, take a 冷水淋浴; 一 could, of course, use 寒冷 immersion of various kinds, 和 你're still going to get 那 exposure of the groin 和 the testicles to 寒冷. Now, I 应该 point out 那 人们 do report, at least anecdotally, 增加 in testosterone as a consequence of 这 practice. 和 I have to imagine 那 they are measuring their serum testosterone, 那 they're not just guessing 那 their testosterone went up. If 你 know of a 研究 exploring 这 directly, please let me know. Put it in the comment section on YouTube 或 even just email me. 我们 have an email 那 你 可以 find at hubermanlab.com. Please email me the reference. I wasn't able to find a reference. 但 I 可以 imagine 二 reasonably plausible mechanisms by which 主动冷暴露 to the groin, in particular the testicles, 会 增加 testosterone.

安德鲁·休伯曼：

The 首先 is somewhat direct, which is 那 anytime 你 cool a 身体 surface, if it's 寒冷 enough, 你're going to get vasoconstriction. 和 then subsequently 你're going to get a rebound 增加 in vasodilation. Meaning 你're going to constrict the 血管 in 那 area, 和 then 之后 the 寒冷 is removed, there's going to be 更多 血流 to 那 area. 和 of course, 血流 relates to organ health 和 组织 health generally. So perfusion of 那 region 和 the gonads, to be 具体的, 与 additional 血液, 你 could imagine in some ways increasing testosterone. 那's reasonably plausible.

安德鲁·休伯曼：

The other, probably 更多 可能 mechanism, relates to the 多巴胺 增加 caused by 冷暴露 那 我们 talked 关于 earlier. Again, anytime 你 have a somewhat stressful stimulus, 但 in particular 与 冷暴露, it seems 那 the catecholamines 去甲肾上腺素, 肾上腺素, 和 多巴胺 all 增加. 和 多巴胺 is known to be in the 通路 那 可以 stimulate testosterone. 和 so while there isn't a direct relationship between 多巴胺 stimulating testosterone, there is an interesting 通路 whereby 多巴胺 增加 可以 trigger 增加 in things like luteinizing 激素, which 可以 trigger 增加 in testosterone, as well as estrogen, 对于 那 matter.

安德鲁·休伯曼：

So I know 那 there are a lot of 人们 out there 那 are interested in the use of 冷暴露 对于 increasing testosterone, 和 some of 那些 人们 和 communities are indeed using 冷暴露 directly on the gonads, on the testes, in order to do 这. I'm not certain 那 那 direct contact is necessary, 和 in some cases it 可能 actually be quite dangerous, 或 你 at least 应该 be careful in terms of the 组织 there 和 avoiding damage. 但 nonetheless, I think 那 a 多巴胺 impact on testosterone is 非常 可能, given the 250% 增加 in 多巴胺 那 have been observed 与 寒冷-水 immersion. 和 all of 那 points to the fact 那 寒冷-水 immersion 非常 可能 增加 testosterone, 但 as a downstream consequence of the 寒冷-水 immersion effects on 多巴胺 和 luteinizing 激素.

安德鲁·休伯曼：

和 again, there's no reason to think 那 the 增加 in luteinizing 激素 wouldn't also 增加 estrogen. Probably not to dangerous 或 水平 那 一 会 want to avoid, 但 I don't think 那 there's anything particularly 具体的 关于 寒冷 对于 inducing testosterone 和 not other 激素. I think it's 非常 可能 那 it 增加 a number of 不同的 激素. I do hope 那 there 会 be a systematic 研究 on 这 in the not-too-distant future. I also hope to not be a subject in the cooling-of-the-gonads experiment.

安德鲁·休伯曼：

Now, I promised 你 the last topic was the last topic, 但 there's 一 other 确实 重要 point 那 I think everyone 应该 be aware of if 你're going to use 主动冷暴露. 和 那 brings us back to the 非常 首先 thing 那 我们 discussed today along the lines of 主动冷暴露, which is 那 你的 baseline 温度 is going to be lowest 关于 二 小时 之前 你 wake up. It's going to 增加 in the 早晨 和 as 你 wake up, 和 增加 throughout the 天 和 下午, 和 then start to drop in the 晚上, 和 come down at 夜间 as 你 head to sleep.

安德鲁·休伯曼：

I also want 你 to remember 那 if 你 are to cool the external portion of 你的 身体, in particular 你的 torso, the net effect of 那 is going to be an 增加 in 体温. So 对于 many 人们, not all, 但 对于 many 人们, if 你 are going to do 主动冷暴露, 你 are going to 增加 你的 核心体温. 和 那 makes sense if 你 think 关于 how 主动冷暴露 可以 增加 代谢 by increasing thermogenesis.

安德鲁·休伯曼：

What 那 all means is 那 if 你 are doing 你的 主动冷暴露 early in the 天, 你 are going to get yet a further 增加 in 核心体温 那 会 be associated 与 wakefulness, 你的 ability to be alert 那 早晨 或 throughout the 天, 和 so on. It also means 那 if 你 do 你的 主动冷暴露 非常 late in the 晚上 或 at 夜间, so 6:00 p.m., 7:00 p.m., 9:00 p.m. 和 so on, 你 are going to 增加 你的 核心体温. 和 if 你 recall, a 降低 in 核心体温 of 一 to 三 degrees is not just beneficial, 但 is necessary in order to get 进入 deep sleep 和 remain in deep sleep.

安德鲁·休伯曼：

So the takeaway 从 这 is, 主动冷暴露 done properly 会 增加 你的 核心体温 和 make 你 feel 更多 alert. So if 你're doing it early in the 天, 那's probably terrific, given 那 most of us want to be alert 期间 the 天. 然而, if 你 do it too late in the 天, 晚上, 或 夜间, it 可以 disrupt sleep by way of disrupting 你的 核心体温. Now, the caveat to 那 is I myself tend to do my 主动冷暴露 early in the 天, maybe not 首先 thing in the 早晨, 但 midmorning, maybe as late as 3:00 或 4:00 in the 下午 in some cases. In the longer 天 of summer, I 可能 do it even later, 5:00 或 6:00 p.m., 和 have no trouble sleeping.

安德鲁·休伯曼：

I have done 主动冷暴露 非常 late at 夜间, 10:00 p.m., 11:00 p.m. 和 so on, as part of a 30-天 challenge of doing 主动冷暴露 every 天 对于 30 天. 和 I got sloppy 与 my timing, 和 then in order to not miss a 天, I 会 do it at 11:00 o'clock at 夜间. 和 I must say I found 那 I could still fall asleep 非常 easily, even doing 主动冷暴露 非常 late at 夜间. 然而, on 那些 particular 天, I was particularly busy, 和 so I was particularly exhausted when I arrived at the 主动冷暴露, 和 I had no trouble falling asleep 之后 doing 主动冷暴露 和 then taking a nice warm shower 和 then going to sleep. 但 I could imagine 那 因为 of the 增加 in 核心体温 caused by 主动冷暴露, 那 were 一 to do 那 too late in the 天, 晚上, 或 夜间, 那 it could indeed disrupt 你的 sleep. So my recommendation 会 be, 对于 most 人们, only do 主动冷暴露 if 你 are prepared to be fairly alert 对于 the next 一, to four, 或 maybe even six 小时 following 那 主动冷暴露.

安德鲁·休伯曼：

So 对于 today's episode, as is the case 与 most episodes of the Huberman Lab 播客, I covered a lot of material. 我们 talked 关于 mechanisms of catecholamines 和 压力 和 pulsatile 释放 of 肾上腺素, 代谢, mental effects, 表现, 无毛皮肤 cooling, 和 on 和 on 和 on. 和 while the goal, of course, is to make sure 那 everyone arrives at 具体的, 非常 clear, mechanistic 和 actionable 方案, I do realize 那 it is an immense amount of information. 和 对于 那 reason, I've created a list of deliberate 寒冷-exposure 方案 aimed at improving mental toughness 和 resilience, 情绪, 表现, 代谢, 减少 炎症, 和 so on 和 so forth. All of 那些 have been condensed 进入 succinct form 和 可以 be found at the Huberman Lab Neural Network Newsletter.

安德鲁·休伯曼：

这 is a monthly 或 semimonthly newsletter 那 我们 释放 那 includes takeaways 从 the podcast 和 方案. 你 可以 access 那些 方案, zero cost, by simply going to hubermanlab.com, signing up 对于 the Neural Network Newsletter; it's 非常 easy to do. 你 just supply 你的 email 和 你 会 receive the newsletter. 我们 do not share 你的 email 与 anybody else. In fact, 我们 have 我们的 privacy policy laid out on the hubermanlab.com website, so 你 可以 find 那 there. 和 the 方案 那 I've designed 应该 make it 非常 straightforward 对于 你 to create a set of 方案 那 你 could use 与 冷水淋浴, 与 寒冷 immersion, 与 或 没有 ice, in combination 与 运动 specifically 对于 一 goal 或 another, 或 to accomplish multiple goals simultaneously.

安德鲁·休伯曼：

If 你're learning 从 和/或 enjoying 这 podcast, please subscribe to 我们的 YouTube channel. 那's a terrific zero-cost way to support us. In addition, please subscribe to the podcast on Spotify 和/或 Apple. 和 on Apple, 你 have the opportunity to leave us up to a five-star review. 你 可以 also now leave reviews on Spotify, so 我们'd appreciate if 你 会 do so. If 你 have suggestions 对于 future guests, 或 topics 那 你 会 like us to cover, 或 feedback generally 对于 the Huberman Lab 播客, please put 那 in the comment section on YouTube.

安德鲁·休伯曼：

Please also check out the sponsors mentioned at the beginning of today's episode; 那 is the best way to support 这 podcast. If 你're not already subscribed to Huberman Lab on Instagram 和 Twitter, please do so. There I cover science 和 science-related tools 那 sometimes overlap 与 the content of the podcast, 但 oftentimes is distinct 从 the information covered on 这 podcast.

安德鲁·休伯曼：

So thank 你 once again 对于 joining me in the discussion 关于 the use of 主动冷暴露 对于 健康与表现. 和 last 但 certainly not least, thank 你 对于 你的 interest in science.

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