we can look at muscle fibers as being on a spectrum with slow twitch on one side
and fast twitch on the other side type 1 which are slow twitch
uses oxygen to create energy the upside is they can work for a longer period of
time before fatiguing the downside is they contract the
slowest when a muscle contracts these are the first fibers to be
recruited then as intensity increases the fast twitch fibers
are then recruited as well type 2a which are fast twitch
uses both stored energy and new energy created with oxygen
just like type 1. the difference is since they use stored energy
they can contract faster than type 1. they can work for a short period of time
before fatiguing type 2x which are the fastest muscle
fibers in humans uses stored energy only this allows it
to contract the fastest but it also means it fatigues the
fastest the thing is these fibers are rarely present in the
average human in a study with sprinters they found
only one out of 1000 muscle fibers they examined were pure
type 2x and finally in between each of these
are hybrids these are muscle fibers that have characteristics of
two or more muscle fiber types although type 2x is rare the hybrid between type
2a and type 2x can be quite common now
let's talk about some of the questions that we might have
starting with probably the most common one can we change our muscle fiber type
for some reason there's a lot of confusion around this
when we actually have research that goes all the way back to the 1970s
which proves that muscle fiber types can be changed
slow can become fast and fast can become slow
according to dr andy galpin who literally examines the fibers of
professional athletes the hybrids are the ones which
are the most likely to change based on your training
and the less training you have the more hybrids you have
how do we know which one we are dominant in the average person
without years of specific training is a mix of type
1 and type 2a with no significantly dominant type
and even though there's several tests that claim they can determine which type
you are the only way to truly find out is by
having a sports scientist stick a needle into your muscle and examine
them individually which one should you focus on for a building muscle
well although fast twitch are known to be larger than slow twitch
there is research that claims that the growth potential between
fast and slow twitch is similar arguing that it doesn't matter whether
you train heavy or not if you turn to failure all of your
muscle fiber types will be recruited the general consensus is that you should
train both in order to stimulate the body in different rep ranges
and intensities however based on what i see endurance athletes which primarily
use slow twitch look very different from the strength in
power athletes focusing on fast twitch which muscles are fast twitch and which
are slow twitch although older muscles are a mix some
are dominant in one type of fiber depending on their function
the calves and posture muscles like the spinal rectors
are going to be predominantly slow twitch since they have to work
all day at a low intensity muscles used for powerful movements like
running or throwing are going to be predominantly fast twitch
such as the hamstring which is used heavily in sprinting at least this is
what it's currently believed since most of the muscle fiber research
is currently done on the quadriceps what research is there
on the muscle fiber types of elite athletes they did one study on
the world champion sprinter they examined the muscle fibers of his quad
and remember type 2 wax are the fastest muscle fibers
that humans can have a normal human being has about zero
percent of these even among elite athletes only a few of
them have shown to have muscles with one percent of these type
2x fibers in this study they found colin jackson
was 24 type 2x fibers what's even
crazier is that this study was done years after he set two world records so
he wasn't even in his prime anymore they also ran tests and found that his
type 2x were twice faster than this type 2a which is the
fast twitch fiber that normal humans aspire to have and 14 times faster than
type 1 slow twitch fibers this guy is a walking superhuman most importantly
let's talk about how we can apply this to our training
if you want more fast switch muscle fibers then you do low reps
max speed or max strength with long rest periods
if you want slow twitch then you just do the opposite of everything i just
mentioned if you want more specific exercises for
fast twitch almost everything in sprint training
will train your fast switch muscle fibers
heavy lifting plyometrics and of course sprinting itself and that concludes this
video if you really want to stimulate those fast switch muscle fibers
quickly hit that like button for me if i said something that was outdated or no
longer true please let me know in the comments
thanks for watching and i'll see you in the next one