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Knowing
your personal muscle fiber make-up can be an invaluable
aid when it comes to properly targeting your training
program. If you're working your muscles in the
wrong way, you'll be cheating yourself out of
hard-earned results.
Every
muscle in your body is made up of a bundle of
small fibers. In each bundle, you have two main
types of fibers: slow twitch and fast twitch.
I will explain exactly what these are in a moment.
The percentages of these different fiber types
that your muscles are made of can help you determine
exactly how you should train each particular muscle
group in your body.
Slow
Twitch:
These
are also known as Type I or red muscle fibers.
They are responsible for long-duration, low intensity
activity such as walking or any other aerobic
activity.
Fast
Twitch:
These
are known as Type 2 or white muscle fibers (divided
further into A and B). They are responsible for
short-duration, high intensity activity. Type
2B fibers are built for explosive, very short-duration
activity such as Olympic lifts. Type 2A fibers
are designed for short-to-moderate duration, moderate-to-high
intensity work, as is seen in most weight training
activities.
By
looking at elite athletes in different sports,
you can see extreme examples of each make-up of
muscle fiber. At the slow twitch end is the endurance
athlete, such as the marathon runner. These athletes
can have up to 80% or more of slow twitch muscle
fibers in their bodies, making them extremely
efficient over long distances. At the fast twitch
end is the sprinter. World-class sprinters can
have up to 80% or more of fast twitch muscle fibers
in their body, making them extremely fast, strong
and powerful but with limited endurance.
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How
to Find Your Muscle Fiber Type:
To
find the predominant fiber type in a particular
muscle in your body, we need to test the repetition
limits of a muscle compared to its maximum strength.
Keep in mind, these limits can be altered by your
training and are, therefore, just rough estimates.
First,
determine your one rep max (known as the 1 RM)
for an isolation exercise for that muscle group,
e.g. the dumbell curl. Find the weight you can
only do one rep with. You want to use an isolation
exercise because any exercise that uses any other
muscle groups will skew the results.
Once
you've figured out your one rep max, take a weight
that is 80% of it (multiply your max weight by
0.8 to get this) and do as many reps as possible
with it.
- If you can
do only 4 to 7 reps with 80% of your 1 RM,
you have mostly fast twitch fibers in that muscle.
The reason you will only be able to do 4 to
7 reps with 80% of your 1 RM is that fast twitch
muscle fibers are strong but don't have great
endurance. You will be able to lift more weight
but you be able to do as many reps with it.
- The ability
to get approximately ten reps with 80% of your
1 RM is the typical fiber-type mix for a
muscle. This works out to about a 50/50 split
between fiber types.
- If you can
do 12 to 15 or more reps with 80% of your 1
RM, your fiber make-up is probably mostly
slow twitch fibers. Slow-twitch fibers are not
as strong but have excellent endurance. This
means you won't be able to lift quite as much
but you'll be able to do a lot more reps with
it.
Repeat this procedure for each muscle group you
wish to determine a type for (it will vary from
muscle to muscle). By knowing what type of muscle
fibers you have, you can tailor your training
towards developing them to their maximum potential.
Though
there are always differences in individuals, there
are some general similarities in fiber types in
muscle groups from person to person.
For
example, in most people, the outer, visible muscle
of the calf (the gastrocnemius) is primarily made
of slow twitch fibers while the soleus (which
lies underneath the gastrocnemius) has a higher
percentage of fast twitch fibers.
Two
more examples of this similarity between people
include the abdominals and the hamstrings. These
two muscle groups are both generally made primarily
of fast twitch fibers.
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How
to Train Your Muscle Fiber Type:
When
you're training with weights, your goal is to
work as many muscle fibers as possible. Affecting
more muscle fibers means greater gains in strength
and muscle mass.
If
your fibers in a particular muscle consist primarily
of slow twitch fibers, in order to affect the
greatest number of those muscle fibers, you'll
need to train that muscle with higher reps, shorter
rest periods and higher volume. This is because
they take longer to fatigue, they recover quickly
and they require more work to maximize growth.
Unfortunately,
slow twitch muscle fibers are limited in their
potential for growth so even if a muscle group
is primarily slow twitch, you should definitely
include some lower rep training to maximize the
fast twitch fibers you've got in that muscle.
If
you find you have a hard time gaining size in
a particular muscle, it could be because it has
a predominance of slow twitch muscle fibers. Higher
reps (e.g. 12 to 15 reps), higher volume (more
sets) and shorter rest periods (30 seconds to
a minute between sets) can help you to maximize
those muscles. This doesn't mean you should use
light weight, though. You should still strive
to use weights that are as heavy as possible that
will cause you to reach failure in those higher
rep ranges. If you don't use heavy weights, you
won't give your muscles a reason to grow.
If
your fibers in a particular muscle group consist
primarily of fast twitch muscle fibers, you're
one of the lucky ones. You'll have a much easier
time building mass in that muscle - fast twitch
muscle fibers have greater potential for size
than slow twitch. The more fast twitch fibers
you've got, the greater your ultimate muscle size
can be. These muscles are most likely your strongest
and quickest to develop.
To
maximize your muscles with fast twitch fibers,
you'll need to train with low to moderate reps
(e.g. 4 to 8 reps), rest periods of around 1 to
2 minutes and a moderate training volume (too
much volume will compromise recovery).
If
your muscles have a fairly even mix of fibers,
you can evenly divide your training between focusing
on the lower-rep, fast twitch fiber training and
the higher-rep, slow twitch fiber training. This
will help you to develop all the fibers in your
muscles, maximizing your ultimate development.
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Training
your muscles according to their fiber type makes
sense. It will help you to get better results
from your training by allowing you to more specifically
target your training according to the exact specifications
of your muscles.
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