How does muscle memory work? I mean, the term gets thrown around so much it's
difficult to know what it even means anymore and depending on who you ask,
you're going to get completely different answer. In fact, we already did an entire
video around the neurological aspect of muscle memory. Well, today's video is the muscles turn.
We're going to see exactly how into what degree muscles "remember" and we're going to discuss
why resistance training might just be one of the most important things you can possibly do
for your health regardless of your age. It's going to be one to remember. Let's do this!
[Intro]
We're really excited
to share that we have a sister come thing called Ava that sells anatomical art like
this one and this one and this one which is mine and Geoffrey's personal favorite
because we have taste and Jonathan does not. If you're interested and want to
support the channel, we'll leave a link in the description below.
Skeletal muscle tissue doesn't divide, meaning that you're born with as many
muscle cells as you're ever going to have in your entire life or at least that's been the
commonly accepted view for decades. More recent studies are starting to show that
there are some interesting exceptions to this rule but they are exceptions
and by far and larged, it still seemed to be accurate that they don't divide.
So, if they don't divide when a skeletal muscle gets bigger what's really happening is those
pre-existing cells are becoming hypertrophic. They are increasing in volume. You see,
skeletal muscle is unique in that the cells are multi-nucleated, meaning that one cell
can have hundreds to thousands of nuclei to help regulate its cellular functions.
This process begins in utero during embryological development. You have these in individual cells
called myocytes that fuse together to create one single gigantic enormous skeletal muscle
cell. The fancy word for this is Syncytium and that's where single cells fuse together
to create a larger cell with various components that are all working together for a single cause.
Now, the reason I'm telling you this is just to provide context as to how
skeletal muscle cells become multi-nucleated in the first place. The real question we're
pursuing here is what happens to that cell during muscle hypertrophy. When hypertrophy
occurs in any cell, there is going to be an increase in intracellular components.
Now, you're gonna have to forgive me for this because this is an absolute terrible drawing,
I'm not an artist but the orange and pink dots are actually meant
to represent intracellular components such as lysosomes, peroxisomes, mitochondria and
for skeletal muscle cells that would include the contractile proteins called Sarcomeres.
Well, since the late 1800s, it's been thought that a nucleus has what's called a sphere of
influence. That means a nucleus is only capable of supporting a specific cellular volume. So,
that means there's an actual size limit for cells because if it gets too big,
the nucleus can't handle it and that cell is in a ton of trouble.
So, you're probably wondering "Well, then how on Earth does a skeletal muscle cell increase
in size when you're working out and it becomes hypertrophic?" There's a size limit. How does that
even happen? Well, the answer is that the skeletal muscle cell steals nuclei from other cells.
Real quick I want to make the sponsor of today's video Athletic Greens. Athletic
Greens is a nutritional company that makes the nutritional drink, AG1,
which is far more than just a greens drink and has become a morning staple for me. AG1 has 75
different ingredients which includes vitamins, minerals, superfoods probiotics and adaptogens.
I just turned 35, which is still very young in the grand scheme of things but my body's
finally starting to feel old for the first time and it's extraordinarily depressing. I mean, look,
in the past five years alone I've discovered I have severe degenerated discs in my low back,
I have a literal broken back, I have an abnormally long colon that is all twisted and turned around,
I grew scar tissue randomly, we still don't know how, that blocked off my small intestine
nearly killing me and this last one's actually admittedly much smaller but I think I'm starting
to get plantar fasciitis and it's really kind of painful but AG1 is not going to fix any of
those and they don't claim to but what AG1 can do is provide me with the essential and
important nutrition that best positions me to adapt and overcome these health issues on my own.
All you do is take one scoop and add it to eight ounces of water and then
shake vigorously. It's super important. I mean, it's not actually a part of the
instructions but it makes me feel happy inside which is all that matters and then
from there you're just going to take a drink and carry on with your day.
I mean, I'm the type of guy that is all about effortless daily habits. So,
knowing that a significant amount of my Essential daily nutrition has been
handled first thing in the morning is a huge weight off my shoulders. If you're interested,
visit athleticgreens.com/humananatomy and they're going to give our audience
a one year free supply of immune supporting vitamin D3, Plus K2 and 5 free travel packs
with your first purchase. Go ahead and find that link in the description below.
In 1961, stem cells were discovered that had the ability to fuse with skeletal muscle cells and
contribute their nuclei. They were called Satellite Cells. Now, normally they exist
in this state of pause called Quiescence and what they require is a signal to activate. Now,
this signal could come from say like an anabolic steroids such as testosterone or it could also
come from tissue injury, say through resistance training but if these cells become activated,
what happens is a daughter cell will fuse with the skeletal muscle cell give its nuclei.
The other daughter cell will then pull back and repopulate the satellite pool and go back into
that state of quiescence waiting for another signal. Now this is all great and dandy but
now we have a new question on our hands; what happens if the cell gets smaller?
Now you've probably heard of the term Atrophy but this is easily one of the most misunderstood
terms in all of biology. Atrophy has nothing to do with cellular death, instead it means
that a cell is getting smaller. So, if a cell undergoes atrophy, let's say from inactivity,
there's no need for that extra nucleus. So, what will happen is a process known as Apoptosis which
is a form of programmed cellular death. So that extra nucleus and the DNA inside of it
will fragment, the MRNA will decay and that is the end of the line for that particular nucleus.
For decades, many biologists assumed what's known as The Myonuclear Domain Hypothesis. It's wordy,
I know but the idea is actually very simple. Again, we're going to pretend that this is
a skeletal muscle cell. So, if it were to become hypertrophic, a satellite cell just
on the outside of it would fuse and contribute its nucleus then if that same cell becomes atrophic,
the nucleus dies. It fragments and everything we just discussed and what you're then left
with is the proper nucleus to cellular volume ratio. Makes a ton of sense,
problem is not every biologist agrees with it.
How is it that one of these nuclei suddenly becomes so compromised that its DNA fragments
and it goes into a downward death spiral but its neighboring nuclei are more or less okay? It's
a pickle for sure and then on top of this, when you're looking at this through optical equipment,
it's difficult to see or know if the nucleus is inside of the skeletal muscle cell or outside
of it - maybe like a satellite cell or a white blood cell, a fibroblast. It's pretty challenging.
It's entirely possible that the other cells, the satellite cells, fibroblasts,
white blood cells, those are the ones that are actually experiencing apoptosis during
muscle atrophy which would explain the measurable markers of apoptosis that scientists are finding.
Well, scientists studying of all things a Tobacco Hawkmoth may have finally found the
answer. You see, during the moth's normal [?] to adult development, something interesting happens
on day 15. Its belly muscles undergo atrophy losing 40% of its total mass which is crazy.
If that happened to you, you would not be doing well. Here's the thing - the moth's
muscles don't have the same satellite cells, fibroblasts, white blood cells that mammals
do meaning that the nuclei that scientists are observing are coming only from skeletal
muscle tissue and when the scientists count the nuclei, they stay the exact
same as they were when the muscles were larger meaning there's no loss of nuclei.
Ask yourself this - what's the advantage to the cell for accumulating new nuclei
and then destroying them shortly after? I mean,
environmental circumstances can shift very quickly for humans going from hypertrophy
to atrophy hypertrophy to atrophy. I mean, just think about the lifestyle of a hunter-gatherer.
Think about it like this - why is it that it's easier to regain muscle mass than build
it initially? Like let's say you put the work in at the gym, right? You lift some weights, you're
building muscle mass through hypertrophy and then bam, you break your arm playing rugby. Obviously,
you're gonna lose the gains in that arm because you're going to spend the next couple months in a
cast and inactivity is a huge driver for atrophy yet as any experienced gym goer can tell you,
it is definitely easier to regain what you lost than build it in the first place and
one of the main reasons that's likely true is the retention of myonuclei.
I mean, think about it - all the cellular adaptations or hypertrophy are already in place
except a recent paper published by James Bagley, Kevin Murach and Andy Galpin suggests that the
myonuclei are only retained for a short period of time. However, despite that, the muscles are still
able to bounce back easier in the long term and it's possible this is due to epigenetic factors.
Epigenetics is one of the most exciting areas of research in biology and for good reason. You see,
DNA doesn't change much and that's actually a very good thing. However, we don't actively use every
gene in our genome. Instead, there are protein markers on the outside of the genes that act
as an on off switch and the interesting part is they are heavily influenced by our environment.
When you do resistance training, you're telling your muscles that there's an actual environmental
need to be stronger and larger. This activates and deactivates epigenetic switches in your genome
making it easier for nuclei to regulate protein synthesis as well as various other factors that
contribute to muscle hypertrophy. This is the muscular component of muscle memory.
Look, your muscles don't have consciousness but they're still able to retain information which
can make it easier to rebound in the event of a loss of muscle mass. I want you to take
a moment and think about what this means for musculoskeletal health as it relates to aging.
Now, Jonathan just did an entire video about resistance training and
how it relates to longevity, so please be sure to check that out but in a nutshell,
resistance training isn't about looking good and getting stronger. I mean,
those are awesome side effects that are obvious mostly plenty motivating for a lot of people
in the world but resistance training is really about stimulating skeletal muscle so that it can
adapt to improve your quality of life and then you want to maintain that as long as possible.
The stronger you are the less susceptible you are to injury. I mean, it's not like you're - it's
impossible to get injured but you're less susceptible and that should be enough for people.
It's not about looking good and getting stronger - again,
that's awesome but what you really should be doing when it comes to resistance training is
focusing on the quality of life improvements and what that's going to mean for you going forward.
Thanks for watching everybody. Geoffrey and I really appreciate you hanging out with us. Now,
all the resources used to make this video are linked in the description below including
an incredible paper from Lawrence Schwartz that this video was heavily inspired from.
Be sure to click the link in the description below to start your Athletic Greens Journey
today and also be sure to check out the link in the description below to our sister company Ava
that makes anatomical art. I mean, come on, you can decorate your house, your office, your car -
probably not your car. That's probably not too safe but all the other places are completely fine.
As always, be sure to like, comment, subscribe if you feel so inclined
and we'll see in the next video.