[Music]
in 490 BC a Greek messenger named fie
deputies ran from the Greek town of the
marathon to the capital Athens to
deliver a message that the Greek army
had just beaten back the Persians now
the distance between those two towns is
26.2 miles and that's the origin of the
modern sporting event that we call the
marathon you might know that story what
they don't always tell you is that when
he got to Athens after those 26.2 miles
but it buddies died so why on earth
would anyone want to run one of those
for fun how are our bodies even able to
I decided to find out so I ran one and
in the process I discovered a lot about
what I'm made of in more ways than one
you guys ready to run a marathon my
training started millions of years
before I ever got to the starting line
the first step to becoming a runner is
well standing up and bipedalism is only
seen in a handful of animals except for
a few species of birds walking on two
legs is only used as a temporary form of
transportation our ancestors first stood
up over three million years ago and well
we were running probably not long after
that we're made for it you could say
that humans are built for long-distance
running but the truth is long-distance
running built us now most
four-on-the-floor quadrupeds could
easily beat me in a sprint but humans
are metal contenders in nature's
distance running events even the cheetah
the most perfectly crafted running
machine on earth can only run for maybe
a mile and a half before it overheats it
today's fastest Olympic marathoners they
would only be beaten by a handful of
Earth's animals in that long distance
one theory of human evolution says that
our adaptations for distance running
were keys to our hunting success like we
talked about in my episode why do we
cook bigger richer meals mean that we
could evolve well bigger richer brains
there's a whole list of ways that we are
made to run in large tubes and our
skulls help us balance while we're
running reflexes and our eyes keep our
heads steady as we move up and down we
have short arms and thin ankles that
take us less effort to swing wide
shoulders thin waists and a pretty
narrow pelvis help us counter the
rotation of our moving legs
we have sweat glands and less body hair
and tall thin bodies that let us
disperse more heat
better blood flow away from the brain to
keep it cool we have big gluteus maximus
muscles to stabilize our upper body
if high surface area need ankle and hip
joints for shock absorption and most
importantly our lower legs are built
like rubber bands this is by far our
coolest running adaptation every time my
body hits the ground it delivers up to
eight times the force of my body weight
that's over 1,400 pounds in order to
keep that up for 26.2 miles my foot
expands and spreads like a shock
absorber this is the most important part
of a running human the Achilles tendon
now my foot hits the ground my calf
muscle is flexed but even then the
muscles and the tendons are still a
little bit elastic and then my ankle
joint acts as a lever which transfers as
much as 50 percent of that energy into
the next step by using stored kinetic
energy instead of chemical energy we're
able to go farther with less work
you can't run a marathon with just
rubber bands though you need power but
humans are on gasoline they require ATP
this is an image of a striated muscle
the same type we have in our arms and
our legs and basically everywhere that
we move each one of those stripes
contains a string of proteins called
actin next to another string of proteins
called myosin of ahead of that myosin
protein well it acts like a ratchet
pulling along on the string of actin and
shortening or contracting the muscle and
that myosin machine is powered by ATP
the thing is our bodies only have a
couple seconds worth of ATP stored up at
any moment so instead we're constantly
replenishing it thanks to our
mitochondria and their little 18-feet
factories just picture me as a giant
ship with trillions of mitochondria at
the oars my body cycled through
something like 75 kilograms of ATP
during the marathon that's almost my
entire body weight just shows you how
good our bodies are at recycling energy
that's 75 kilograms of ATP broken down
released the same amount of free energy
as a kilogram of TNT my body gets ATP in
a couple of different ways if I was
running full-speed the entire time my
cells would be forced to use an
inefficient process called glycolysis
but by running slightly slower for the
whole race I let my mitochondria use a
much more efficient method called the
Krebs cycle and the electron transport
chain I can burn lots of fuel and make
that ATP like fat or protein but my
muscles preferred glucose which is
stored in long chains called glycogen
for quick access but even they don't
keep that much just lying around so
instead I topped off my glycogen tank
before the race by doing something
called carb loading look at how these
law holds I have to eat but even eating
all of that before the race my body
can't hold all the glycogen it needs to
get through a marathon so I had to eat
and drink more during the race or else I
would hit the dreaded wall
hitting the wall is just a big scary
name for fatigue and there's lots of
reasons why it can happen if you run out
of glycogen then your muscles can run
out of ATP and that protein ratchet will
get stuck in the locked position
it's actually why something well gets
kind of stiff when it dies if your cells
don't have enough salt then your nerves
and muscles won't have the sodium
potassium and calcium that they need to
pass electrical signals the main reason
that people hit the wall is because of
this so your brain is competing with
your muscles for blood sugar and if
those levels dip to low you'll feel
dizzy and loopy
[Music]
your brain is actually preventing your
muscles from firing to go to some sort
of emergency Power Save mode I've never
run a marathon before and I discovered
it's not like any other sporting event
I've ever taken part in you're not
battling an opponent you're only
battling yourself all those feelings of
joy and fatigue and pain they only exist
in your mind but that mind is connected
to the physical muscles and chemical
power plants and proteins doing work
I've never understood more about my body
or my biology and when I push them to
the limit and in the process I
discovered that it wasn't a limit after
all that was the most fun they never
want to have again like halfway through
is like the hardest thing I've ever done
and the entire second half was just pure
willpower it's like a competition
against yourself and i1b might even have
in mind
that was awesome thank you everybody
we're not the only social animals that
sit down to eat together but we are the
only ones who cook cultural
anthropologist Claude levi-strauss says
above all cooking establishes the
difference between animals and people
although I think he'd agree that pants
make a big difference too