#239 ‒ 力量、肌肉与延寿训练的科学 | 安迪·加尔平博士（第一部分）

所以我们可以从血液中提取它，如果血液中的量变低，我们还可以从肝脏中提取。

So we can pull that out of the blood and then we can actually, if that gets low, we can pull that out of the liver.

这就是基本的能量代谢途径，而肝脏则充当了葡萄糖的备用储存系统，确保你在组织中糖原浓度变化时仍能调节血糖水平。

So that's the basic like energy pathway and the liver then functions as kind of your backup storage system for glucose to make sure that you can regulate blood glucose while you're changing concentrations of glycogen in tissue.

这正是它的作用，因为正如你多次提到的，你当然不希望血糖出现大幅波动，那是很糟糕的。

That's really what it's doing because you don't want, obviously as you've talked about a million times, a bunch of instability and blood glucose, that's a bad thing.

这是人体会优先调控的四大要素之一，其他还包括pH值、血压和电解质浓度。

It's one of the four things that your body will regulate over almost anything else in addition to pH and blood pressure, etcetera, and electrolyte concentrations.

它们根本不愿意去干扰这些指标。

They don't like to mess with those things at all.

其他所有生理过程都会围绕这些指标进行调整，以维持它们的稳定。

So everything else will move around those things to keep those stable.

好的，那么现在我们回到组织层面，过了报纸之后，接下来会是一大块木头。

All right, so if we're in the tissue now and we've got past our newspaper, the next thing it would be a giant piece of wood.

如果你有柴火之类的东西，在野外生火是非常困难的。

So if you had firewood or something like that, lighting firewood in the wild is very difficult to do.

这不会在几秒钟内发生。

It doesn't happen in seconds.

你需要知道该怎么做，但这会给你带来成倍增长的燃烧时间。

You need to kind of know what you're doing, but it's going to give you exponentially more fire length.

我的意思是，你把一根木头放在火上，第二天早上醒来时它可能还在燃烧，能持续数小时。

I mean, you could put a log on a fire and that could literally be on going the next morning when you wake up and give you hours.

把这想象成脂肪。

Think about that as fat.

我喜欢这个类比：如果你对脂肪和碳水化合物的化学结构有点了解，它们都是长长的碳链。

Now I like this whole analogy is if you know a little bit about the chemistry of fat versus carbohydrate, they're both big long chains of carbon.

就像纸实际上是用木头做的，它只是同一种物质的另一种形式。

Just like a paper is actually made of wood, it's sort of just a separate piece of the same thing.

你可以从葡萄糖中得到一个六碳链，而脂肪则可以有不同长度的碳链，比如十八碳脂肪酸，你可以把三个这样的脂肪酸连接到甘油骨架上，形成一个含有约五十个碳原子的甘油三酯。

So you get a small six carbon chain from glucose, You can get any number of lengths of chains of fat, 18 carbon fatty acid chain, you can put three of those on a backbone of glycerol and you've gotten yourself 50 carbon molecules per triglyceride or something like that.

这里的化学计量关系更优。

Stoichiometry gets better here.

每分子脂肪你大约能获得300到400个ATP，这才是真正更优的地方。

You're going to get something like 300 or 400 ATP per molecule of fat, and that's where things get actually better.

好的，脂肪主要来自肌肉外部。

Okay, the fat is actually coming mostly though from outside of the muscle.

因此，脂肪动员产生的能量在全身相对均匀分布，而葡萄糖则主要来自肌肉内部，再辅以少量储备来源。

So energy from fat mobilization comes throughout the body somewhat evenly, glucose comes mostly from the intra muscle itself, and then a little bit from the backup supplies.

如果能量不足，磷酸肌酸会直接从肌肉中释放。

If it gets low, phosphocreatine comes directly from the muscle.

说了这么多能量背景，当你开始运动并试图产生锻炼效果时，我们漏掉了哪一部分呢？

All that energetic background to say, when you start moving and you start trying to create exercise, where's the last piece we forgot here?

哦，是蛋白质。

Oh, that's protein.

所以在这个类比中，蛋白质更像一块金属。

So protein actually in this analogy would be functioning more like a piece of metal.

如果你在森林里有一块金属，又需要生火，而除此之外什么都没有，理论上你确实可以用火来熔化金属。

So if you had metal in the woods and you needed a fire and you had absolutely nothing else, you can in theory melt metal with a fire.

你会得到一些能量，但这是一种效率极低的方式。

You're going to get some, but it is a very, very low end proposition.

如果你非得这么做，为了生存也可以做到。

If you absolutely have to do it, you can do it to survive.

但如果你把这当作主要的能量来源，那就麻烦大了，因为在野外金属会很快耗尽。

But if that's your fueling strategy, you're in a big, problem because you're gonna run out of metal very quickly in the woods.

你就没得用了。

You're out of it.

它还是你建造庇护所、维持稳定、获取食物等一切生存所需的关键资源。

It's also the only thing you have to create shelter and stability and to fend for food and everything else.

所以从提供能量的角度看，这虽然理论上可行，但却是最糟糕的选择。

And so it is a plausible way to provide energy, it's just a terrible one.

它的主要作用是让你重新制造工具。

It's mostly there for you to reconstruct new tools.

所以如果你在野外有金属，需要制作一把刀，你就可以把它加工成刀具。

And so if you're in the woods and you have metal and you need to make a knife, you can fashion that.

好的，现在我们需要把这东西熔化，做成一个屋顶，我们可以把它打造出来。

Okay, now we need to melt that thing down and make a roof, we can fashion that.

现在我们需要再次熔化它，做成一把铲子。

Now we need to melt that back down and make a shovel.

它的设计本意是被拆解后，以相同或不同形式重新塑造为同一种基本物品。

It's meant to be kind of broken back down, recreated in the same and different forms of the same basic item.

所以，这正是我们所关注的。

And so that's really what we're looking at.

能够在碳水化合物和脂肪之间切换作为不同的能量系统，这确实很重要，但我们今天没时间深入讨论，这也不是最重要的。

The ability to play back and forth with carbohydrate and fat as different fuel system, that's really, we don't have time to get to that today, it's not really the best thing.

但蛋白质在组织中的作用和必要性，它并不是能量来源。

But the ability and the need and the point of protein in tissue, it is not fuel.

尽管如我所说，它理论上可以作为能量来源，但它的真正作用就是如此。

Although it can be for what I explained, it's really that.

我们需要做的是，现在主要把它用在这一项任务上。

It's taking it and saying, need it mostly for this task right now.

我们主要需要它来维持骨骼肌。

We need it mostly for skeletal muscle.

我们主要需要它来支持免疫系统。

We need it mostly for immune system.

我们主要需要它来支持这些其他功能。

We need it mostly for these other functions.

因此，快速流失肌肉的一种方式是让自己处于不利状态，因为身体会权衡：是保留24英寸的肱二头肌，还是优先满足免疫需求，它会选择后者。

And so one of the ways to quickly lose muscle is to put yourself in a compromised position because it's going to say, if we're choosing between keeping that 24 inches bicep or clearing up something we need immunologically, it's going to go towards that.

这也是为什么我们会看到蛋白质在肌肉间的重新分配。

This is also why we see protein redistribution across muscle.

比如，你花大量时间锻炼肱二头肌，让它们变得非常大，但却不训练小腿。

Like say you spend a bunch of times on your bicep and your biceps get really, really big and then you don't train your calf.

假设你的蛋白质摄入不足。

And let's just say your protein intake is insufficient.

你就会开始将小腿的蛋白质重新分配到肱二头肌，以支持其生长。

You will start redistributing proteins from the calf up to the bicep to actually enable that growth.

所以你以为自己在变壮，但实际上如果蛋白质摄入不足，你只是从其他部位挪用了资源。

And so you're thinking you're getting bigger, but you're really just taking it from other places if protein intake itself is not sufficient.

因此，这确实是一个基石。

And so it really is a cornerstone.

如果你查阅相关研究，就会清楚地看到这一点。

And if you look at the research, you're going to see this very clearly as something.

如果你曾疑惑为什么有些人对蛋白质摄入如此执着，为什么这成了如此重要的事，那是因为它是你无法从其他地方获取的原材料。

If you ever wonder why some of these people are just so diligent about protein intake and why this has become such a big deal is it's the raw material you really can't get anywhere else.

你可以获取碳水化合物和脂肪，并通过多种方式实现这一点。

And you can get carbohydrates and fat and you can go through that whole thing in a lot of ways.

但蛋白质是无法造假的。

You can't fake protein though.

要做到这一点非常具有挑战性。

This is very challenging to do so.

最后我想说的是，这对我如此重要的原因是，没有蛋白质，你几乎不可能真正地构建肌肉。

And the last little piece I'll say there is why this is so important to me is you can't fake muscle most specifically without the protein.

当我们开始流失肌肉时，就会引发一系列从身体表现开始的问题。

And when we start losing muscle, now we enter a whole cascade of problems from physical performance.

你的兴趣更偏向于衰老和长寿。

Your interest is more of like aging and longevity.

整个连锁反应就变成了一个问题。

That whole cascade becomes a problem.

然后我们当然可以讨论肌肉的具体变化，并回顾你之前提到的一些细节。

And then we can certainly talk about the specific changes in muscle and pass some of the details you've actually covered before.

是的，这些事情变得真的非常重要。

Yeah, those are things like it just becomes a really big deal.

因此，在这一点上节省是完全没有意义的。

So it just doesn't make any sense to skimp on that one as a place to go.

对。

Yeah.

值得重复一下。

It's worth repeating.

当你观察人们一生中的肌肉质量，并根据他们拥有的肌肉量进行分类时，我们应该谈谈这一点，因为当然，我对数据的解读是，一旦将力量标准化，力量才是关键，但测量肌肉质量相对更容易。

When you look at people across their lifetimes and you evaluate for muscle mass and you divide people up and categorize them by the amount of muscle mass they have, And we should talk about this because of course my interpretation of the data is that once you normalize for strength, strength wins, but it's sort of easier to measure muscle mass.

你知道，你只需要让人做一次双能X射线吸收测定法（DEXA），就能大致算出他们的ALMI，因此我们通常根据ALMI来观察生存曲线，对听众来说，ALMI指的是四肢瘦体重相对于身高的标准化指标，即四肢瘦体重指数。

You know, all you need to do is put somebody in a DEXA and you sort of can figure out their ALMI and so we tend to look at survival curves based on ALMI, which for the listener just means the amount of lean muscle you have in your arms and legs normalized to your height, appendicular lean mass index.

毫无疑问，肌肉越多，寿命越长。

There's no ambiguity about the fact that more muscle means a longer life.

这一点就像高VO2 max意味着更长寿命一样清晰。

It's as clear as high VO2 max means a longer life.

那么现在让我们回到基础，确保大家理解肌肉的结构，因为我想谈谈不同类型的肌纤维，以全面介绍一些生理学知识。

So let's now go back and make sure people understand the structure of a muscle because I wanna talk about different fiber types as well, to round out some of the physiology.

为了理解快肌纤维和慢肌纤维之间的差异——它们在代谢上有区别——我想知道它们在结构上有什么不同，也许你可以简单解释一下肌原纤维是如何工作的，以及类似的内容。

So in an effort to understand the difference between fast twitch and a slow twitch muscle fiber, which has a metabolic difference, I'm curious as to what the structural difference is and maybe just kind of explaining how myofibrils work and things like that.

让我稍微回退一点，来理解人类的功能和运动。

Let me go back just a little bit to understand human function, movement.

不过我不会在这上面深入太多。

I won't go as deep into this one though.

如果你只是思考一下你是如何实际产生动作的，它实际上有三个核心功能。

If you just think about how you actually create movement, it really has three core functions.

首先，你必须有一个方向或信号，这将来自你的神经系统。

So number one, you have to have some sort of direction or signal, and this is gonna be coming from your nervous system.

无论是中枢还是外周，无论是自主神经还是受控的躯体反应，对于这场对话来说其实都不重要。

And so whether this is central peripheral, whether this is autonomic, whether this is a controlled somatic action response, it doesn't really matter for this conversation.

神经必须告诉肌肉该做什么。

The nerve has to tell it what to do.

所以，神经这一部分你已经明白了，就这些。

So nerves, you get that one, that's it.

不要再从神经系统中去考虑其他东西了。

Don't take anything else nervous system.

你已经获得了这种控制。

You get that control.

现在，这条神经必须进入肌纤维，并告诉该肌纤维收缩。

Now that nerve then has to go into a muscle fiber and tell that muscle fiber to contract.

好的，肌肉纤维是第二部分，细胞本身必须收缩，但这并不会直接产生运动。

Okay, the muscle fiber then is part two, so the cell actually has to contract itself, but that actually doesn't cause movement.

肌肉并不是直接附着在骨头上的，事情不是这样运作的。

Muscles are not attached to bone, That's not how it works.

肌肉纤维被结缔组织所包围。

So muscle fibers are surrounded by connective tissue.

所有这些结缔组织会被捆绑成一个整体。

All those connective tissue are bundled together in like a package.

如果你想象从肉铺买回一捆培根条，他们会用保鲜膜把它们包起来，肌肉的结构其实就有点像这样。

So if you imagine buying a bunch of strips of bacon from the butcher and they would wrap that up and kind of Saran wrap together, that's actually kind of what a muscle looks like.

所以，这层保鲜膜把它们连接在一起。

So you've got that Saran wrap connecting it.

如果你拉其中一条培根，你会发现整包都会跟着动。

So if you pulled on one piece of bacon, you'd notice the whole package moves.

这正是关键所在。

That's sort of the point.

你正在通过结缔组织将力量从肌肉传递出去。

You're transferring force from muscle through connective tissue.

这些结缔组织汇聚成肌腱，而肌腱则附着在骨骼上。

That connective tissue comes together into a tendon and that tendon then attaches to bone.

因此，人类运动的第三部分实际上是结缔组织。

And so the third part from a human movement is actually connective tissue.

因此，你需要一个信号，需要肌肉收缩，使结缔组织拉动骨骼，这才是产生人类运动的关键。

And so you have to have a signal, you have to have a muscle contract that has to make connective tissue pull on a bone, that actually is what generates human movement.

如果你看前端，我们把神经科学留给其他人，只看结缔组织，就会发现很难理解它在发生什么，原因有很多，但最主要的是它不具备可塑性。

Well, if you look at the front end, we'll leave the neuroscience to other people, you look at the connective tissue and it's very difficult to understand what's happening there for a number of reasons, but mostly it's not plastic.

当我们观察肌肉时，它的可塑性非常强。

When we look at muscle, it's tremendously plastic.

我的意思是，它能适应，并对许多因素做出快速而迅速的改变。

And what I mean by that is it adapts, it changes very quickly and rapidly in response to a lot of things.

结缔组织没有血液供应，没有能量需求，它只是在那里存在着。

Connected tissue doesn't have a blood flow supply, it doesn't have energetic demand, it's kind of just there.

这个故事还有更多内容，但我们先说到这里。

There's more to that story, but we'll just kind of leave it like that.

适应性问题的核心——无论是正面还是负面的——都在于骨骼肌。

The core of the issue of adaptations, whether they are pro or negative, is going to be in skeletal muscle.

这就是实际情况的样子。

And so here's what that actually looks like.

神经会延伸下来，附着并支配大量的肌纤维。

A nerve will come down and actually attach and innervate to a whole host of muscle fibers.

你可以想象，肌细胞是整个生物学中直径最大的细胞之一。

And so you can imagine, cellular muscle fibers are some of the largest cells in all of biology by diameter.

它们在人类身上非常巨大。

They're tremendous in humans.

事实上，真正让人类特别的是，我们的肌纤维被称为多核细胞。

In fact, what's actually very interesting about humans that makes us special is our muscle fibers are called multinucleated.

你可能在医学院或类似的地方听说过这个术语。

And so you probably remember this term from med school or something like that.

事实上，每当我跟生物学领域的人聊这个，他们都会震惊，因为我都忘了自己在运动科学里陷得多深。

In fact, whenever I talk to biology people about this, their head is blown because I forget how lost in exercise science I get.

在自然界中，看到一个细胞拥有多个细胞核是非常罕见的。

It's very uncommon in nature to see cells that have more than one nucleus.

细胞核可以说是细胞的核心，它承载着你的DNA。

And the nucleus is the core of the cell, if you will, that's what holds your DNA.

它控制着细胞何时复制蛋白质以生长、收缩、死亡或修复，是整个细胞的控制中心。

It tells you when to replicate proteins to grow, shrink, die, repair, so the whole control center.

因此，骨骼肌细胞中拥有如此多的细胞核，这可不是几个，也不是两三个，而是每细胞数千个。

So the fact that skeletal muscle has many of them per cell, in fact, it's not a few, it's not two or three, it's thousands per cell.

所以骨骼肌可以变得异常庞大。

So skeletal muscle can be extraordinarily large.

我 somewhere 有个相关的视频。

I have a video of this somewhere.

我想不起来了。

I can't remember.

实际上，我们之前做的一期《男性健康》杂志里可能有一张图片。

Actually, there might have been a picture in a men's health thing we did.

somewhere 有一段视频。

There's a video somewhere.

我们会找到那段视频，并且也会把它放在节目笔记里。

We'll find that, and we'll also put that in the show notes.

好的。

Okay.

我实际上可以用镊子夹起一根人类的肌纤维，而且肉眼就能看到。

I can actually pick up a single muscle fiber from a human with tweezers, and you can see it with your naked eye.

所以我们可以拿着它，事实上，如果我现在有一根，我可以在镜头前举起来，你们就能看到一个完整的肌细胞，它们就是这么大。

So we could hold this, in fact I could do it right now if I had one, I could hold in front of the camera, you'd be able to see an actual whole muscle cell, they're that large.

而且它们可以非常非常长，长度可达几英寸。

And in fact they can be very, very long, so they can be several inches in length.

让我们帮大家理解一下，通常在肌肉以外的地方，我们是用细胞膜和单个细胞核来定义一个细胞的。

Let's help folks understand what defines because normally outside of the muscle, we kind of define a cell by a cell membrane, has a single nucleus.

我的意思是，我们大致知道这里的组成成分。

I mean, we kind of know what the constituent of elements here.

这也由细胞膜定义，但它看起来更像一个细长的管状结构，而不是球形。

This is defined also by a cell membrane, but it's a sort of a longer looking tube as opposed to a sphere.

这个区分很好。

Good distinction there.

我们又容易陷入运动科学的细节里。

Sort of again get lost in exercise science.

如果你还记得高中生物课，当时把细胞想象成一个圆圈或椭圆，其实它就是这样，是圆形的，但呈管状。

If you remember like back to high school biology and you think of a cell as like a circle or an oval, it's like that, it's circular, but it's a tube.

所以它是一个非常长的管子。

So it's a very long tube.

可以把它想象成一条马尾辫。

The way to think about it is like a ponytail.

当你想到马尾辫时，你会觉得它是一个整体，确实是一条马尾辫，但它是由许多细长的管状头发组成的。

So if you think about a ponytail, you think about it as one thing, it is a ponytail, but it's made up of a whole bunch of long tube individual hairs.

它们全部缠绕在一起形成一条马尾辫。

And they all wrap together to make a ponytail.

这就是骨骼肌细胞的外观，实际上与心肌细胞非常不同。

That's what a skeletal muscle cell looks like, which is actually quite different than a cardiac cell.

那些细胞更接近矩形，较短且较宽。

Those are more rectangular, if you will, that they're shorter and wider.

骨骼肌纤维非常长、非常细，但仍然是圆形的。

Skeletal muscle fibers are very long, very narrow, but still circular.

它们仍然具有细胞膜。

They still have a cell membrane.

它们拥有多个细胞核。

They have a bunch of nuclei.

大多数细胞器与其他细胞基本相同。

Most of the organelle are the same as any other thing.

收缩单位我们稍后再讲，但这就是它们的基本结构。

The contractile units we can get to in a second, but yeah, that's the basic setup of them.

给我一个骨骼肌细胞的典型长度。

Give me the typical length of a muscle cell, a skeletal muscle cell.

你无法给出一个典型的数值，因为骨骼肌的结构取决于其功能。

You can't really give a typical because depending on what you'll see with skeletal muscle is structure is function.

所以，如果你将这与心肌组织对比的话。

So if you contrast this to cardiac tissue.

心肌组织其实非常有趣，因为它是我们所说的终极慢肌纤维。

So cardiac tissue is actually quite interesting because it is what we call the ultimate slow twitch fiber.

所有心肌组织都是慢肌纤维。

And so all the cardiac tissue is slow twitch.

事实上，慢肌纤维比骨骼肌的还要更慢。

And in fact, slow twitch are even more slow twitch than the skeletal.

而且它们通常相当均匀。

And they tend to be fairly uniform.

因此，你可以给出关于横截面积、直径和长度的具体数值。

So you could give specific numbers on cross sectional area, a diameter length on those.

骨骼肌，如果你看看你的缝匠肌，就是从你髋部前侧那个尖突部位延伸到膝盖内侧中部的那块肌肉，理论上这些肌纤维可以贯穿整个长度。

Skeletal muscle, if you look at your sartorius, which is that kind of muscle that goes from that pointy part of the front of your hip down to the inside middle of your knee, theoretically those fibers could run the whole length.

一个单独的细胞？

A single cell?

没错。

Correct.

可以贯穿整个长度。

Can run that whole length.

是的。

Yeah.

即使它只延伸一半那么长，也已经非常长了。但如果你回过头去看眼肌，那就会小得多。

Even if it runs half that length, that's extraordinarily You go back though and you'd go to like an ocular muscle, it's going to be minor.

它会非常小。

It's going to be extremely small.

如果你看看手指上的肌肉，它们会非常、非常、非常短。

And like if you go to muscles and you digitize your fingers, they're going to be very, very, very, very short.

并没有一个典型的范围。

There is no like classic range.

长度可能从几毫米到几英寸不等。

It could be from millimeters to literally inches in length.

所以，这些细胞具有多个细胞核的原因，大概是为了解分散细胞构建的调控功能。

So presumably the reason that these cells have multiple nuclei is basically to decentralize the actions of cellular construction.

因此，你有DNA在靠近细胞核的地方转录成RNA，再输送到高尔基体合成蛋白质。

So you've got DNA making RNA in the proximity of that nucleus coming out onto the Golgi making protein.

如果你有一个长达一厘米的细胞——那已经大得离谱了。

And if you had, for example, even a one centimetre long cell, which is enormous Outrageous.

你不可能仅靠一个细胞核来管理整个细胞的所有活动。

You couldn't simply make all of that work with one nucleus.

所以问题来了，这些细胞核是独立运作的吗？

So the question is, does that mean these nuclei act independently?

那么，谁是这里的中央指挥中心？

Where's the central command on this?

这似乎是一个非常棘手的问题。

It seems like a remarkable problem.

棘手的问题，巨大的优势。

Remarkable problem, remarkable advantage.

这里也是同样的情况。

It's the same thing here.

难以控制，但极具适应性。

Hard to control, but amazingly adaptive.

没错。

Exactly.

完全正确。

This is exactly right.

如果你想要深入探讨成核问题，这会变得非常有趣，因为我们的实验室已经证实，许多职业运动员每单位体积的细胞核数量更多。

So if you want to dive down the entire nucleation question, this gets very, very interesting because we've actually shown in our lab that a lot of professional athletes have more nuclei per volume.

因此，我推测这或许就是他们能够如此良好适应的原因。

So this is one of the things that I posit is maybe this is why they can adapt so well.

他们之所以能承受如此大的训练量，正是因为周围有更多这些肌核。

It's why they can handle the volume that they can handle is they just simply have more of these nuclei around.

你认为这有多少是遗传因素，有多少是训练适应的结果？

And you believe that that is how much genetic and how much adaptation to training?

我很想给你一个明确的答案。

Well, I would love to give you an answer there.

这两方面都会有一些影响。

There's going be a component to both.

我们确实知道许多生活方式因素会影响这些机制，但最新的数据正在揭示这一点。

We actually know numerous lifestyle factors are going to influence these things, but the more recent data are showing this.

通常来说，我们认为肌核具有几个特点。

In general, we have thought that nuclei have a couple of things.

首先，不仅仅是肌核的数量重要，这是我们过去的想法。

So one, it's not just nuclei count that matters, which is what we previously thought.

形状也很重要。

The shape matters.

有球形的，有椭圆形的，还有各种各样的形状。

There's like spheres, there's ovals, there are all kinds.

看起来形状决定了功能。

And it looks like the shape determines the function.

位置也决定了功能。

The location determines the function.

因此，似乎存在一些围绕线粒体的核亚型。

And so it looks like there are subtypes of nuclei that surround, for example, the mitochondria.

它们专门负责线粒体的修复。

And they're going to be very specific to mitochondria repair.

还有其他类型的核则更专注于外围区域，负责细胞壁损伤的修复。

And then there's other types that are more specific to periphery that'll do cell wall damage.

还有一些核则专门调控损伤反应。

And then there are some actually that are regulating injury specifically.

这目前就是它的样子。

This is what it looks like right now.

因此存在多种亚型，这是非常近期才有的新认识。

And so there are subtypes, and this is very, very recent understanding.

这可能就是为什么有些人比其他人更能恢复和应对损伤的原因——他们只是恰好拥有更多这种亚型。

And this is probably why some folks recover and respond to injury more than others is they just simply have more of this subtype.

关于天性与教养的问题，难点在于这里的测量精度很难保证，而且技术发展得太快了。

Now to your question of nature versus nurture, what's challenging about that is the measurement fidelity here is difficult and the tech is moving quickly.

但每隔几年，当显微镜技术提升时，我们就会发现前三年的很多结论都被推翻了。

But it's sort of like every couple of years when the microscopes get better, we sort of realize that all the three previous years are now invalidated.

因此，观点一直在反复变动。

And so there's just a lot of movement back and forth.

事实上，如果你关注细胞生长的相关研究，比如是否属于肥大，关于这些结构在生长中所起作用的问题，目前仍存在极大混乱。

And in fact, if you look at this related to cell growth, whether it was hypertrophy, there seems to be tremendous confusion about the role of these things in growth or not.

过去我们曾提到过一个概念，叫做单核域限制。

So there used to be a thing that we referred to as a mononuclear domain limitation.

换句话说，一个细胞的生长会受到限制，这便是你的肌纤维。

So in other words, a cell would only grow, so this would be your fiber.

它只会根据细胞核能够控制的范围来增大体积或直径。

It would only hypertrophy or grow in diameter to the extent at which the nuclei could control it.

因此，为了获得更多的生长，你实际上需要更多的卫星细胞介入并增加细胞核数量。

And so in order to gain more growth, you actually have to get more satellite cells to come in and add nuclei.

当你停止训练时，细胞的直径会缩小，但你仍会保留单核细胞的数量。

And then when you detrain, that cell goes back down in diameter, but you preserve the mononuclear number.

因此，再次训练时比第一次更容易了。

And so then now retraining is easier than it was the first time.

我的意思是，这简直难以置信，但这就是所谓的肌肉记忆老话：重新获得曾经拥有的肌肉，比从零开始长出新肌肉要容易。

I mean, is unbelievable, but this is the old adage of muscle memory, quote unquote, it's easier to regain muscle you once had than to put on muscle you never had.

我从未听过对这一现象的分子层面解释，但这是一个非常合理的机制。

And I've never heard a molecular explanation for that, but that's a very plausible mechanism.

但现在看来，这并不正确。

Now it looks like that's not correct though.

你保留了这些细胞核。

You retain the nuclei.

看起来那并不正确。

It looks like that's not correct.

有意思。

Interesting.

我觉得这是一个反复来回的过程。

It's very back and forth is the way I'll say it.

所以确实存在某种东西。

So something is there.

我刚刚向你描述的这个故事，直觉上是说得通的。

The story I just outlined to you, it makes intuitive sense.

我曾经对此热衷了好几年。

I got really hot on it for a number of years.

然后，一些更具挑战性的数据出现了，我们觉得并非如此。

And then it was like some more challenging data came out and was like, well, we don't think so.

我只能说，每周都有新的论文发表，然后我们就又回到这个话题上。

I'm just going have to say, this is like every week another paper comes out and it's just like, okay, now we're back on it.

现在我们又退出了。

Now we're back off.

现在我们意识到其中存在亚型，与某些因素相关，他们就说：‘天啊，好吧。’

And now we realize there's subtypes in line with where, and they're like, oh shit, okay.

这显然适合进行纵向研究。

It will lend itself obviously to a longitudinal type study.

我的意思是，在理想情况下，你会选择相对年轻、可塑性强的青少年运动员，长期跟踪他们在不同训练需求下的变化。

I mean, in an ideal world, you would take relatively young, presumably pliable athletes in their teens and study them over time under different training demands.

显然，最理想的情况是用同卵双胞胎来做研究。

Obviously the dream case is doing it with identical twins.

我们已经做过这个了。

Which we've done.

所以我完全可以打断你一下。

So I could just totally interrupt you.

如果你愿意，我们可以聊聊那个双胞胎研究。

We can go to that twin study if you want.

我们先把这个放一放，因为我还想回头解释清楚这些机制是如何运作的。

Let's put a pin in it because I want to come back to making sure people still understand how these things work.

所以我们现在已经确认，肌肉细胞与其他任何细胞都不同。

So we've now established that muscle cells are kind of unlike any other cell in the body.

它们对能量的需求有多高？

How hungry are they for energy?

举个例子，当我们谈到肝脏时，大家总认为肝脏是个很棒的器官，也许没肌肉那么酷，但它在我心中有特殊地位，因为我一直认为，之所以没有体外肝脏支持系统，是因为我们根本无法复制它的复杂性。

So for example, when we look at the liver, you know, always think of the liver as a beautiful organ, maybe not quite as cool as the muscle, but it has a special place in my heart because I've always argued that the reason there is no extracorporeal support for the liver is we simply can't replicate its complexity.

对听众来说，体外意味着在身体之外。

For listeners, extracorporeal means outside of the body.

比如，透析是肾脏的体外支持系统，VAD或ECMO是心脏或心肺联合的体外支持系统，呼吸机是肺的体外支持系统。

So dialysis is extracorporeal support for the kidney, a VAD or an ECMO is extracorporeal support for the heart or heart and lungs combined, a ventilator extracorporeal support for lungs.

但我们无法为肝脏做到这一点。

We can't do that for a liver.

如果患者不幸因过量服用泰诺而试图自杀，并发展到肝脏不可逆损伤的地步，你无法为他们提供肝脏支持系统，只能等待移植。

If a patient tragically overdoses on Tylenol in an attempt to take their life and they reach a point of irreversibly damaging the liver, you can't put them on liver support until they get a transplant.

如果这个病人没有接受肝移植，大约两天内就会死亡。

That patient will be dead in about two days if they don't get a transplant.

这其实归结为你之前提到的很多内容。

And I it comes down to a lot of the stuff you already talked about.

葡萄糖稳态是人体最重要的稳态机制之一，其调控的精确程度是我无法想象的。

Glucose homeostasis, one of the most important bits of homeostasis in the body is controlled with a level of precision I can't fathom.

我可以像你谈论肌肉那样，充满热情地谈论肝脏。

I can sit and talk about the liver with the same level of excitement that you talk about the muscles.

但有趣的是这一点。

And yet here's what's interesting.

肝脏并不是一个代谢需求旺盛的器官。

The liver is not a metabolically greedy organ.

是的。

No.

它本身并不会消耗太多能量。

It really doesn't on its own consume much energy.

相比之下，大脑是一个非常复杂的器官，一个极其耗能的器官，这或许正是我们需要肝脏来支持大脑的原因。

The brain, by contrast, a very complex organ, an incredibly metabolically greedy organ, which is probably why we need the liver to support the brain.

如果没有肝脏如此出色地维持葡萄糖稳态，我们的大脑要么需要演化出远离葡萄糖的适应策略，那样我们的大脑就不会有现在这么大的体积。

Without the liver being so good at maintaining glucose homeostasis, our brain would have either needed an adaptation strategy away from glucose, where we wouldn't have brains as large as we do.

肌肉在这个层级结构中处于什么位置？

Where does the muscle fit into this hierarchy?

肌肉在何处算得上是一个高耗能的器官？

Where is the muscle a high maintenance organ?

肝脏的有趣之处在于，它就像一位职业拳击手，你即使狠狠揍它很多次也没关系。

What's cool about the liver, it's kind of like a professional fighter where like you can beat it up a lot.

没错。

That's right.

你对肾脏几乎无能为力。

You can't do much for the kidneys.

它们根本没有耐受力。

They just don't have sustainability.

我对肝脏有一种次级的热爱，因为它是人体中最接近骨骼肌的器官，它会倾听、会响应，也能发生变化。

I have like a secondary love for the liver because it's the closest thing in the body to skeletal muscle in terms of the fact that it is listening and it will respond and it can change.

正如你所说，它非常具有适应性。

And as you said, very adaptive.

极其适应。

Super adaptive.

如果你还不知道的话，你会对这个感到惊讶的。

You'll appreciate this if you didn't already know it.

在我住院医师期间，我们做过不少活体肝移植手术。

When I was in my residency, we would do quite a number of live donor liver transplants.

这种手术是让一个人捐出自己肝脏的三分之一到一半，移植给另一个与之HLA配型非常好的人。

So this would be an operation where an individual donate a third to a half of their liver to another individual where there was a really good HLA match.

但真正有趣的是。

Well, here's what was really interesting.

那部分肝脏再生的速度快得惊人，如果你不预先用大量静脉注射的磷来应对，他们就会发生严重的代谢危机。

The speed with which that portion of their liver would regenerate was so staggering that if you didn't anticipate it with inhumane doses of intravenous phosphorus, they would have an enormous metabolic crisis.

是的，完全说得通。

Oh yeah, totally, that makes sense.

无论给这个人多少食物，都不可能提供足够的磷酸盐来支持肝脏再生所需的DNA、RNA和蛋白质合成。

There was no amount of food you could give this person to allow them to have enough phosphate backbone for the DNA and RNA and protein synthesis that was going to be necessary to reproduce their liver.

所以你只能不停地给他们静脉注射磷酸盐。

So you just had to basically be giving them IV, Phos, nonstop.

这听起来就像我们在做单根纤维实验时必须对纤维做的事情。

Sounds like what we have to do with fibers when we're doing our single fiber experiments.

就像你得让它们浸泡在溶液里。

Like you have to bathe them.

你得持续不断地提供磷酸盐。

You just have to have a permanent path of phosphorus.

它们哪儿也去不了。

They won't go anywhere.

没错。

That's right.

他们能在两周内再生出三分之一的肝脏。

And they could regenerate a third of their liver in two weeks.

这简直令人震惊。

It's simply staggering.

当然，对听众来说需要注意的是，这只有在肝脏结构保持完整的情况下才有效。

And now of course, the caveat for the person listening is this only works when the architecture of the liver is preserved.

一旦进入肝硬化和炎症的阶段，就无能为力了。

So once you cross into the path of cirrhosis and inflammation, it's over.

所以不幸的是，对于那些肝脏严重受损的人，比如患有非酒精性脂肪性肝病、非酒精性脂肪性肝炎或酒精性肝病的患者，当达到一定程度后，肝脏就不再具备再生能力。

So unfortunately, that person whose liver has been so beat up, for example, status post NAFLD, NASH, or alcoholic liver disease, you get to a point where it no longer has that capacity to regenerate.

你知道，这个故事中比较好的一点是，如果你在那之前及时干预，还是有很大希望的。

You know, the kind of the nice part about the story is though, if you fix it before that, you have a good chance.

没错。

Absolutely.

你可以长时间放任不管，但只要你还没达到那个临界点就采取行动，几乎就能恢复到原状。

So you can mess up for a long time, but if you do take that action before you hit that level, I shouldn't even say it this way, but you can almost get back to scratch.

在那里你可以获得大量的再生和恢复。

You can get a lot of regeneration there and a lot of recovery.

你说得对。

You're right.

肾脏对血压如此敏感，对高血糖的损伤如此敏感，肺部对吸烟之类的东西也是如此敏感。

And the kidneys being so sensitive to blood pressure, so sensitive to the damage of high glucose, the lungs being so sensitive to smoking and things like that.

我只是觉得肝脏是人体中被忽视的英雄。

I just think the liver is an unsung hero of the body.

它是让你坚持下去的关键，就像是撞墙了。

It's the thing that keeps you like, it's the bonk.

你知道，在耐力运动中，当肝脏耗尽时，不管你有多强的意志力都没用。

You know, those from endurance sports, like when the liver is finished, it doesn't matter how much mental strength you have.

一切都结束了。

It is a wrap.

你就要撑不住了。

You are going down.

如果你肝脏被击中，看看任何体育比赛，肝脏被击中是瞬间发生的。

If you get hit in the liver, if you watch any sports, you get hit in the liver instantaneously.

你直接瘫了。

You're crippled.

这没关系。

Doesn't matter.

即使你心理上还撑得住，身体也会停止运作，让你倒下。

You can be mentally you're there, your body will seize and shut you down.

这不就是奥斯卡·德·拉·霍亚对阵伯纳德·霍普金斯时发生的情况吗？

Isn't that what happened to Oscar De La Hoya against Bernard Hopkins?

你还记得那场比赛吗？

Do you remember that fight?

我不记得那场比赛了，但我看过它五百遍。

I don't remember that fight, but I've seen it 500 times.

我经常和UFC拳手合作，这周末我还为我的一位选手主推了一场比赛。

I work a lot with UFC fighters and a number of I've actually headlined fight this weekend for one of my guys.

所以是的，我在这些运动中见过很多次。

So yeah, I've seen it in those sports a ton.

我见过脚趾尖轻轻碰到肝脏，世界冠军就立刻僵住，倒在地上。

I've seen a little toe, just the tip of a toe click the liver, and world champions just get locked up and fall off the ground.

肝脏不喜欢被这样刺激，但大多数情况下它能承受住打击。

It does not like being aggravated like that, but it will handle a beating for the most part.

你可以把它打得挺惨的。

You can beat it up pretty good.

如果你看一些血液化学指标，比如ALT、AST，你会发现，哦，你的情况还不错，只要采取正确措施，它会很快恢复。

And if you see like any blood chemistry stuff and if you're looking at ALT, AST stuff and you're like, ah, you're pretty, it'll come back pretty quick if you take the right steps.

肾脏才是你一看到就意识到‘糟了，这次真的回不来了’的器官。

The kidney is the one you see when you're like, uh-oh, we're not coming back from this one.

好的，我们再回到肌肉。

All right, so going back to muscle.

肌肉对你的所有行为都极其敏感，并且在积极响应。

It's tremendously responsive to everything you're doing and it's listening.

所以你问的是它在能量消耗上有多高。

So your question of how energetically demanding it is.

关于这一点，有几点要说。

There's a couple of things to say about this.

人们经常会说，如果你增加更多肌肉质量，会提高你的基础代谢率。

People will talk a lot about, hey, if you add more muscle mass, that's going to elevate your basal metabolic rate.

所以你只是坐着也会燃烧更多卡路里。

So you'll burn more calories just sitting there.

这确实是真的，但并没有达到你想象的那种程度。

That is true, but it's not to a level that you actually think.

我认为数据大概是每单位30卡路里左右。

It's probably I think the numbers are something like 30 calories.

增加多少肌肉质量才会这样？

With how much increase in muscle mass?

每磅。

Per pound.

每磅。

Per pound.

好的。

Okay.

我想大概是这样的。

Think I it's like something like that.

这并不是一个恒定的水平，你可以说，经过三四年之后，多出的那五到十磅肌肉。

It's not actually level and you can make the argument, well, after three or four years, that is that extra five or 10 pounds.

好吧，当然。

Okay, sure.

但并不是像有些人认为的那样，他们的基础代谢率会因为增加五磅肌肉而从每天1500卡路里飙升到2500卡路里。

But it's not like, I feel like some people think it's gonna go from their basal metabolic rate's gonna go from 1,500 calories a day to 2,500 because they put on five pounds of muscle.

这完全超出了实际情况的范围。

That's just way outside the realm of what's gonna happen.

你有很多理由应该增加一些肌肉，但并不是为了提升代谢率。

There are many reasons you probably wanna put some muscle on, but like adding the metabolic boost.

这是因为问题在于它们的能量消耗有多大？

And that's because the question is how energetically demanding are they?

实际上，换个角度想一想。

Actually think about it the opposite.

骨骼肌其实挺懒的。

Skeletal muscle is pretty lazy.

它希望尽可能高效，因为如果你考虑生理功能，你希望大脑能尽可能长时间地全速运转。

It wants to be as efficient as possible because if you think about functionality of physiology, you want your brain running full course as often as you possibly can.

你希望持续感知外界发生的事情，同时进行内省。

You want continual interception of what's happening in your outside world as well as introspection going on.

它还在做决策等等。

It's also making decisions, etcetera.

骨骼肌只是像一个后备系统。

Skeletal muscle is simply like a backup system.

你更应该这样想：老板，你需要我做什么？

It's thinking more about it as like, what do you need done, boss?

你需要做点什么来提升你的状态吗？

You need something done to elevate your function?

我们这就去办。

We're on it.

如果不需要，我们就坐下来闭嘴，等着被稍微推一下。

If not, we're gonna sit down and shut up and wait to be sort of pulled a little bit.

这意味着，如果你现在需要能量，肌肉就会立即行动。

And so what that means is if you need energy now, muscle will jump to action.

它会让你动起来。

It'll get you going.

我们在各种现象中都能看到这一点，比如吃肉。

We see this from everything from meat.

如果你有消耗200卡路里的能量需求，你的脚就会开始抖动，你会不自觉地做各种小动作。

It's like if you have this energetic need to burn 200 calories, your foot will start tapping, you'll start doing sort of all these things.

这就是骨骼肌在发挥作用。

That's skeletal muscle going.

跟大家说说NEAT是什么。

Tell folks what NEAT is.

这是非运动性能量消耗。

This is non exercise energy.

它指的是你日常消耗的能量，但不包括体育活动、锻炼，也不包括维持生命所必需的能量，比如呼吸、消化和基本生理功能。

So it's energy you're burning that's not physical activity or exercise or the energy needed to survive, to breathe, to digest, to go through basic stuff.

因此，这是全天能量消耗中另外大约10%的部分，这部分能量的波动会显著影响人是减重、不减重还是增重，具体取决于你的新陈代谢健康状况、总体体型以及其他因素。

So it is the other 10 or so percent of energy throughout the day that accounts for people losing weight or not losing weight or gaining weight that fluxes pretty well depending on your metabolic health, depending on your total size, depending on your other stuff.

所以，如果你见过那些坐不住的人，

So if you ever see those people who are like, man, they just can't sit still.

那些人通常被通俗地认为是NEAT水平比较高的人。

Those are like colloquially the people that probably have a pretty high knee.

他们只是坐着，就在不断消耗能量。

So they're just burning energy kind of sitting here.

而那些身体更静止、更沉稳的人，NEAT水平则相对较低。

Other people who are more stoic physically are going to have sort of a lower thing.

这也是解释为什么人们能在截然不同的热量摄入水平下，保持相同的运动表现和健康状态的原因之一。

This is also one of the things that explains how people can maintain the same amount of physical training, like exercise performance, as well as health at tremendously different levels of calorie intakes.

因为我们可以迅速调整非运动能量消耗，你的身体就像是最后的打磨、最后的上漆。

Because we can adjust meat very quickly and your body is it's kind of like a last bit of polish, last bit of paint.

那么，我们这里需要做些什么呢？

Like what do we need to do here?

这其中存在巨大的缓冲空间，你可以增加或减少。

There's huge buffer in there where you can Yeah, increase, decrease

并根据你的需求进行调整。

and depending on what you need to do.

因此，我们可以某种程度上改变我们的代谢设定点，以维持相同的体重，无论热量摄入如何上下波动。

And so we can kind of change our metabolic set point, if you will, to keep you at the same body size, irrelevant of going up and down in calories.

我肯定你们和莱恩讨论过这个问题成千上万次了。

And I'm sure you guys cover that a thousand times with Lane.

那么，我们来谈谈收缩吧。

So let's talk about contraction.

收缩是如何实际发生的？为什么收缩需要ATP？

How does a contraction actually work and why does a contraction require ATP?

收缩的哪个部分需要它？

What part of the contraction needs it?

如果我们回溯一下，神经是传入骨骼肌的。

If we go back, nerve is coming into skeletal muscle.

在某些情况下，比如眼睛，我们有一个叫做运动单位的结构。

And it would, in some instances like the eye actually, we have what's called a motor unit.

所以我们在所有这些结构中都有运动单位。

So we have a motor unit across all these things.

运动单位指的是传入的神经以及该神经所支配的所有单个肌纤维。

So motor unit is the nerve that's coming in as well as all of these single fibers that that nerve is innervating.

这意味着在眼睛中，例如，运动单位小到几乎是一对一，即一个运动单位传入并激活一根肌纤维。

So what that means is in the eye, for example, you have motor units as small as almost one to one, which means there's a single motor unit coming in and activating a single muscle fiber.

这赋予了你极高的精细控制能力。

That gives you extraordinary control of dexterity.

因此，有很多神经进入以控制非常少的肌纤维，这让你能精确地控制动作的具体位置。

And so you have a lot of nerves coming in to control a very small number of fibers that makes you have real high precision with exactly where you're controlling.

将这与臀肌这样的肌肉对比一下。

You contrast that to muscles like the glutes.

你需要臀肌产生很大的力量和爆发力，但对精确度要求很低。

You need a lot of strength, force production of the glutes, but very low fidelity.

你不需要在髋关节伸展时有很高的准确性，

You don't need accuracy of hip extension in terms of

基本上就只有一件事。

There's basically just one thing.

就是收缩，不是不收缩。

It's contract, not contract.

我的意思是，尽最大力量去做。

I mean, do it with as much force as possible.

或者不。

Or not.

所以你会有数百个。

And so you're gonna have hundreds.

你唯一需要调节的维度就是收缩的力量和速度？

That's basically the only dimension you have to regulate is what is the force and speed of contraction?

而眼睛就是一个很好的例子，很高兴你做了这个对比，我们的眼睛具有极高的精确度。

Whereas with the eye, which is a great example, I'm glad you made that contrast, our eyes have insane fidelity.

当然，你有多个眼外肌。

And of course you have multiple interocular muscles.

很多，是的。

A lot, yeah.

你有这些位于眼睛上下及两侧的所有肌肉，为了让人能够如此出色地完成我们擅长的事情——用眼睛细微地捕捉目标，需要进行大量的精细调节。

You have all of these muscles above, below, on the side of the eyes, and the amount of tuning that has to happen to allow humans to be able to do what we do so well, which is very subtly pick things up with our eyes.

如果将这与手指对比，我们需要手指具备很高的精确度，但眼睛的精确度和运动准确性仍然高出一个数量级。

If you contrast that to like your fingers, which we need to have, it's the second highest level of fidelity we have to have, the eyes are still an order of magnitude higher in terms of fidelity and accuracy of movement.

根本无法相提并论。

It's not even close.

我的指尖需要非常精确，但我的眼睛在精确度上达到了一个全新的层次。

I need to be very precise with my fingertips, but my eyes are on a whole new level of precision of where we have to be.

所以在眼睛中可能是1:1或1:2，而在臀部肌肉中，每个运动单位可能达到数千个。

So if there's one to one or one to two in the eyes, it could be thousands per motor unit in the glutes on off.

在50%、20%的收缩水平下，你能够保持直立姿势，同时让臀部维持约20%的收缩力，以完成完全的髋关节伸展、垂直跳跃爆发、深蹲或硬拉等各种动作。

On 50%, 20%, so you can stand erect while having some sort of like 20% level of glute contraction to full hip extension, vertical jump explosion, squat deadlift, whatever the case.

这太棒了。

That's so fantastic.

好的，继续。

Okay, continue.

所以神经来了。

So nerve comes in.

神经进来后就实现了这一点。

So nerve comes in and does that.

现在还有其他几层机制，我不打算深入讲神经方面，但我想你肯定熟悉这个原理。

Now here's a couple of other layers Without going too far into NERV, you're familiar I'm sure with said principle.

因此，你针对姿势需求有特定的适应性。

So you have specific adaptation for pose demand.

这里还有另一个原则，叫做亨内曼大小原则。

There's another principle in here called Hennemann's size principle.

埃尔伍德·亨内曼是我最喜爱的科学家之一。

So Elwood Hennemann's one of my favorite scientists.

这个原则基本上说的是存在低阈值和高阈值的运动单位。

Principle basically says there's low threshold and high threshold motor units.

这意味着有些运动单位很容易被激活，而有些则必须狠狠刺激才能让它们启动。

And what that means is there are some motor units that are very easy to get turned on, and some that you have to just aggravate the shit out of them to get them to turn on.

我们得确保大家明白，从动作电位的角度来看，这到底意味着什么？

Let's make sure people understand what that means in terms of what's an action potential?

神经究竟是如何传递信号的？

How does a nerve actually deliver its signal?

我们在化学、电学和化学之间有着这种有趣的相互作用。

We have this fun interplay between chemistry, electricity, and chemistry.

这正是肌肉收缩的工作原理。

That's exactly how contraction works.

所以你需要从电信号转变为化学信号，再变回电信号。

So you have to go from an electrical signal to a chemical signal back to an electrical signal.

所以主要涉及的是钠、钾和氯离子。

So what happens is you've got sodium and potassium, and chloride are your main players.

而氯离子带负电荷。

And chloride is a negative charge.

钾当然是正电，钠也是正电。

Potassium, of course, is positive and sodium is positive.

如果你忘记了，这里有个有趣的方法来记住：彼得，你可能比我更熟悉这个——可以查一下‘医生协助病人安乐死’。

The fun way to look up this and pay attention to this if you ever forget here is, Peter, you're probably more familiar with this than I am, but look at Patient Assisted Suicide with Doctor.

莫尔基安。

Morkian.

如果你给一个人注射大量钾离子，他们的心脏会逐渐停止收缩，最终停止跳动。

You give a giant bolus of potassium to somebody and they're just going to slowly stop, their heart's going to slowly stop contracting.

为什么？

Why?

因为细胞内的钾离子浓度会变得与细胞外的钾离子浓度大致相等。

Because the amount of potassium intracellular is going to become fairly equivalent to the amount of extracellular potassium.

因此，细胞内外之间的电势梯度变得中性，于是不会产生动作电位。

And so the change in gradient electrically between the outside of the cell and inside of the cell becomes neutral, and so no action potential occurs.

因此，你需要的是细胞外与细胞内之间的电势变化。

And so what you need to have happen is a change in electrical volt from outside the cell to inside the cell.

通常我们说的是细胞内大约负30毫伏，这只是一个大概的数值。

And typically we're talking like negative 30 millivolts intracellular, it's kind of a number.

一旦足够的钠离子和钾离子开始朝正确的方向移动，电性就会发生变化，因为我们的正电荷变得更负，你明白吧。

And once enough of the sodium potassium start moving in the correct directions, then the electricity changes because our positives move more negative, you get the idea.

然后，啪的一下，我们触发了这个开关的翻转。

And boom, we hit this flip of this switch.

这就是我们所说的全或无原则。

And this is what we call all or none.

因此，骨骼肌纤维无法以不同的力量水平收缩。

And so skeletal muscle fibers can't contract at different levels of force.

我的意思是，一旦激活，它们就会完全收缩。

What I mean is once you flick them on, they go on fully.

而这是它们唯一能够收缩的方式。

And that's the only way they can contract.

因此，我们在本科课程中使用的类比是电灯开关。

And so the analogy we use here in our undergraduate class is the light switch.

一旦达到那个特定的毫伏阈值，肌纤维就会以最大力量收缩。

So once you hit that certain threshold of millivolt, the muscle fiber contracts as hard as it possibly can.

这里没有调光开关这种可能。

There is no way, there's no dimmer switch here.

你无法实现80%、85%或50%的收缩强度。

You can't go 80%, 85, 50.

一旦达到动作电位，就是100%的收缩。

It's 100% once you get to that action potential.

你实际上会看到毫伏值急剧回升。

You actually see the millivolts just rocket back up.

然后就会发生一整套恢复过程。

And then there's this whole cascade of recovery.

这就是你的钠钾泵在努力重置离子梯度，把离子重新归位，以便你能再次收缩。

This is what your sodium potassium pumps are doing to try to reset that gradient, put them back in the right direction so you can have another contraction.

这实际上解释了强直收缩的原因。

Again, this is actually what explains tetany.

所以，如果你在纤维恢复之前连续多次刺激它，它就会感觉像在进行等长收缩。

So if you contract that fiber multiple times in a row before it gets back to reset, then it just feels like it's in an isometric contraction.

这其实并不是它的真正机制，但你会有这种感觉。

It's not actually how it works, but it's gonna feel like that.

真正完全中断这个话题的是：你拥有大量的肌纤维，它们以极快的速度收缩和放松，让你的肌肉感觉整个都僵住了，但实际上它们正在不断开关。

What actually totally stops the topic, but what actually happens is you have so many muscle fibers and they're contracting and relaxing at such a fast rate to your muscle, it feels like the whole thing's just locked up, but they're actually flicking on, flicking off.

顺便说一下，为了让大家理解，解释一下为什么尽管单个肌纤维的行动电位和收缩都是全或无的，但肌肉整体仍能产生不同强度的力量。

And by the way, just so folks understand, explain to folks how despite an all or none action potential and an all or none contraction of a single fiber, you can still get variable degrees of strength at the level of the muscle.

这是下一部分。

So this is the next part.

这就是为什么我们必须提到亨内曼大小原则。

This is why we had to bring up Hennemann's size principle.

在这些运动单位中，存在不同的尺寸。

So within these motor units, you have sizes.

有趣的是，在正常情况下，一个运动单位内的所有肌纤维通常属于同一种类型。

Now what's interesting is most of the time in normal situations, all the muscle fibers in that motor unit are of the same fiber type.

假设我们有两个运动单位。

Let's just say we had two motor units.

其中一个运动单位是慢肌纤维，另一个则是快肌纤维。

One of those motor units is slow twitch, and one of those motor units is gonna be fast twitch fibers at interface.

所以，无论一个运动单位中有五根纤维还是五百根纤维，现在其实并不重要。

So if we had five fibers in that motor unit or 500, it doesn't really sort of matter right now.

实际上我们有几个因素在起作用，但它们通常都属于同一类型的纤维。

We have a couple of factors actually coming on, but they're gonna be of all like type generally within that same motor unit.

因此，我们调节力量产生的唯一方式就是这样的。

So the only way that we relegate force production is this.

我们必须知道，这五个肌纤维一旦被激活，都会以最快速度收缩。

We have to know that all five of those muscle fibers, once they get turned on, are gonna contract at full speed.

因此，我们真正改变整块肌肉产生力量大小的方式，就是改变被激活的运动单位数量。

So the only way we actually change how much force we're creating a whole muscle is by altering how many of these motor units get turned on.

所以，大小原则告诉我们，我们会先激活阈值较低的运动单位。

So the size principle tells us we're going to turn on the low threshold units first.

因此，如果你去做你刚才做的动作——伸手去拿一杯水，最好别激活那些高阈值、高力量输出、通常更大（虽然不总是）的运动单位，它们通常含有更快的肌纤维，也通常更大。

And so if you go to do what you just did, so you reached over and grabbed a glass of water, it's probably best we don't turn on our high threshold, high force production, generally larger, not always, but generally larger motor units that have generally faster fibers that are generally bigger.

有两点原因说明你为什么不该这么做。

Number one are two reasons why you don't want to do that.

第一，我们会产生不必要的力量。

Number one is we produce unnecessary force.

结果不是轻轻把杯子送到嘴边，而是把杯子砸到脸上。

So instead of slowly touching that glass to your lips, you'd smash them off your face.

你不能往下减力。

You can't go down.

如果一个运动单位能产生五磅的力，而你只需要两磅的力，那就无法回退。

So if that motor unit can produce five pounds of force and you need two pounds of force, there is no way to go backwards.

因此，你总是从最小的单位开始，只有在需要更多力量时才激活更多的运动单位。

So you always start at the smallest unit possible and turn on more motor units if more force production is required.

其次，这会消耗能量。

Secondarily, it just burns energy.

快肌纤维比慢肌纤维代谢需求更高，所以这样做会浪费能量。

So fast twitch muscle fibers are more metabolically demanding than slow twitch muscle fibers, and so you're going to waste gas doing that.

这正是你的汽车从一挡、二挡依次起步的原因。

This is exactly why your car starts off in first gear, second, etcetera, etcetera.

我们随着挡位升高会损失效率，但会获得性能。

We lose efficiency as we go up, but we gain performance.

所以让我们用这个例子，快速回到运动员身上。

So let's use that example when you're talking, just going back really quickly to the athlete.

所以当我想要做硬拉时，这个反应有多快被调节？

So how quickly is that response modulated when I want to deadlift something?

你可以在现实生活中看到这一点。

You can see this in real life.

我有一段视频，是我一个朋友做硬拉时的场景：在这里，首先会激活低阈值的慢肌运动单位，这些单位几乎对应于慢肌纤维。

I have a video of a deadlift actually from a friend of mine doing this where so the initial step that's gonna happen here are you're gonna activate slow twitch, lower threshold motor units, which are gonna be almost exposed to the slow pitch fibers.

我们目前所知的唯一增加这种激活的方式，就是通过力量需求。

The only way that we really know to increase that is through force production demands.

当我们谈到衰老相关的肌纤维类型时，还会再回到这个话题。

Like we're gonna come back to this when we get to fiber type stuff eventually for aging.

甚至这周有些新研究结果出来了，你可能还没看到。

And some of the stuff that came out even this week, you may have not seen yet.

快肌纤维的挑战在于，根据这一逻辑，它们只在高阈值需求——也就是高力量需求下才会被激活。

The challenge with fast switch muscle fibers is they're only then based on this logic activated under high threshold demands, which are high force demands.

你可以做任何事来激活它们，而关于衰老的数据会证明这一点。

You can do anything to activate and the data will show this on aging.

随着年龄增长，慢肌纤维几乎没有任何减少。

You see virtually no reduction in slow twitch fibers with aging.

它们的尺寸也没有减少。

You see no reduction in size.

事实上，有一些研究表明，衰老会导致慢肌纤维出现肥大效应。

In fact, there's some more than a few papers showing a hypertrophic effect of solvent fibers of aging.

VLO没有减少，比张力（即单位尺寸的力）也没有减少，力量也没有下降。

There is no loss in VLO, there's no loss in specific tension, which is like force per unit of size, there's no loss in power.

只要保持任何程度的活动，就很容易维持和保护慢肌纤维的健康。

It just appears to be very easy with any level of activity to maintain and preserve health of solvent fibers.

但由于快肌纤维需要力量输出，而日常活动中通常不会产生高强度的力量，因此这些纤维会长时间得不到利用。

But because fast food fibres require force production and you generally don't get high force production and activities of daily living, then those fibres go unutilized for long stretches of time.

最终，它们会逐渐消失。

Eventually they go away.

因此，我们看到一种非常有趣的现象，称为肌纤维类型分组，神经会认为：‘这个纤维没有被使用。’

And so what we see happen is this really interesting thing called fibre type grouping, where the nerve will basically say, okay, that fibre is being not used.

整个运动单位会退化，但肌纤维会被保留。

That whole motor unit will decay and the fibres will be preserved.

其他相邻的运动单位会生长出新的延伸，激活一些 previously lost 的运动单位，并将这些纤维转化为该先前运动单位的纤维类型。

The other neighboring motor units will actually grow new extensions, activate some of the previously gone motor units, and then convert those fibers into whatever fiber type happens in that previous motor unit.

因此，总体来看，我们观察到的是慢缩纤维开始吸收快缩纤维，或者慢缩运动单位开始吸收快缩纤维并将其纳入自己的运动单位中。

So in general, what we see happening here is slow twitch start absorbing, or slow twitch motor units start absorbing fast twitch fibers and bringing them to their motor unit.

因此，我们在肌肉中看到大片单一类型的纤维区域。

And so we see these large patches of single fiber types throughout the muscle.

因此，这个谜题的最后一部分是：在一个运动单位中，这些纤维由同一个神经元支配，且属于同一种纤维类型，但它们并不彼此相邻。

And so the last part of that puzzle is in a motor unit, those fibers are connected by the same neuron and they're the same fiber type, but they're not laying next to each other.

你并不希望它们集中在同一个位置。

You don't want them in the same spot.

它们大致分散在整个肌肉中。

They're sort of dispersed throughout the muscle.

因此，这使得肌肉收缩更加平滑。

And so that gives you smoothness of contraction.

所以其中一个现象是，如果你开始像整个右臂肱二头肌是一个运动单位那样出拳，而整个左臂是另一个运动单位，当你单独收缩其中一个运动单位时，就会出现极度痉挛、失控，产生抽搐且不受调节的运动。

And so one of the things that happens is if you start punching like the entire right side of your bicep is one motor unit, the entire left side is when you contract that motor unit alone, get super spastic, out of control, and you get twitchy and unregulated movements.

因此，当我们看到衰老过程中出现这种纤维类型聚集现象时，这几乎完全是快肌纤维的问题，而不是慢肌纤维的丧失。

And so when we see this fiber type grouping thing occur with aging, it's almost exclusively a problem of fast twitch fibers, not loss of slow twitch fibers.

这也解释了运动控制精度下降，以及可能存在的精细运动控制问题。

And so that also explains lack of fidelity as well as potentially some problems with fine unit movements.

快肌和慢肌在不同区域的混合程度如何？

What is the heterogeneity of fast and slow twitch mixtures within different areas?

所以可以推测，眼睛的肌肉全是慢肌纤维。

So presumably the eye is all slow twitch.

它并不特别需要很大的力量。

It doesn't particularly require much force.

它不需要太大的力量，但需要非常快的速度。

It doesn't require much force, but it does require a lot of speed.

因此你需要能够快速来回移动。

So you need to be able to dart back and forth quickly.

所以实际上我不知道

So I actually don't know the

让我们看看一块大的骨骼肌，比如背阔肌或臀大肌。

Let's look at a big skeletal muscle like the lats or the glutes.

所以这里我们需要关注两点：人与人之间的差异非常大。

So we have two things you have to pay attention to here is we have a huge amount of person to person variation.

但在什么范围内呢？

Within what bracket though?

给我一个概念，假设每个人至少都有20%的每种类型，我这只是随便说的，但真的存在吗？

Give me a sense of presumably everybody has at least 20% of each, I'm making that up, but is there?

我先回答第二部分，然后再回过头来处理第一部分。

Let me do the second part, we'll come back to that first part.

所以正如你刚才提到的，肌肉与肌肉之间也存在巨大的差异。

So there's actually, as you alluded to a second ago, there's also tremendous difference between muscle to muscle.

因此，如果我们比较一下我的比目鱼肌和你的比目鱼肌，你的比目鱼肌可能是90%的慢肌纤维，而我的可能是70%。

And so some muscles, if we look at it, like if we compare my soleus to your soleus, you might be 90% slow twitch in your soleus, I might be 70.

这在那块肌肉中会是一个很大的差异。

And that would be a large variation in that muscle.

如果你观察动物模型或细胞培养，比如小鼠模型，你会看到跟腱中100%都是慢肌纤维。

If you look at animal models, cell culture, meaning murine, like you're gonna see 100% slow twitch in a soleus.

原因是我们走路，跟腱必须是大部分为慢肌纤维。

And the reason is because we walk, the soleus has got to be a majority slow twitch muscle fiber.

你知道，我们花太多时间在行走上，不能冒这个系统效率低下的风险。

You know, we just spend too much time ambulatory to risk any inefficiency in that system.

100%。

100%.

如果你总体来看小腿，那里主要有两块运动肌肉。

If you look at the shank in general, you've got two primary muscles of movement there.

跟腱是较小的那块，它们都附着在你的脚底。

The soleus being the smaller one, they both attach to the bottom of your foot.

那就是你的跟腱，对吧？

That's your ponteres, right?