There arethree types of muscle tissue found in your body: cardiac,
smooth, and skeletal. Skeletal Muscle is further divided into 3 types
of muscle fibers (Type I, Type IIa, Type IIb) The different types of
muscles are determined based on certain functional and structural
characteristics.
Cardiac Muscle - is obviously found in the heart.
It looks very similar to skeletal muscle as it is made up of
individual "cable" looking strands but the big difference is each strand
can work individually as well as in a group. Cardiac muscle is mostly
an involuntary muscle which means you don't have to think about it to
make it work.
Smooth Muscle - is found around internal organs and
blood vessels. Smooth muscle tissue is flat and smooth and looks
somewhat like a bed sheet. Its main function is to provide support to
the internal organs and to help move things along as in the lining of
the stomach and intestines. Like cardiac muscles it is mostly an involuntary muscle.
Skeletal Muscle - is found all over your body and is the focus of most of your
workout routines (Biceps, Quads, Abs, etc.) Skeletal muscles look like
steel cables with lots of individual fibers working together to form
each muscle group. They are both voluntary and involuntary allowing us
to move at will but also helping us to react when something happens to
us. Skeletal muscles are responsible for walking, standing, lifting,
jumping and pretty much every type of movement you can think of.
Skeletal
muscle is further divided into 3Types (Type I, Type
IIa, Type IIb).
Type I - are often referred to as Slow Twitch
Muscles. Type I fibers are used for activities that don't require much
strength but do require lots of endurance. Your postural muscles, the
muscles that keep your back erect, are a good example of Type I muscle
fibers. The leg muscles that you use for walking are another Type I
muscle fiber.
Type II - are also called Fast Twitch Muscles. Type
II fibers enable you to perform powerful movements that don't require
very much endurance. They usually kick in when an activity requires
more than 25% of your total strength. They are commonly more abundant
in shorter more compact muscles such as Biceps and Triceps. Type II
muscle fibers are further divided into Type IIa and IIb.
Type IIa
fibers are mostly used for activities that use a lot of strength that
lasts for up to a couple of minutes.
Type IIb fibers are used when
you need a burst of power but only for a few seconds. These fibers are
the largest of all the fibers and should be the focus of your lifting
if you want to build large, bulky muscles. (Lifting as much weight as
possible for 3-5 reps)
Most skeletal muscles are made up of a
combination of all 3 types of muscle fibers. The percentage of each
muscle fiber plays a large part in your body structure. People with a
large portion of Type I muscle fibers tend to be long and lean and good
at endurance activities such as marathon running. People with a bigger
portion of type II muscle fibers tend to have short, bulky, powerful
muscles and are better at activities like sprinting and weight lifting.
In general when you perform an activity the Type I fibers kick in first
and then if more strength is needed the Type IIa then the Type IIb
fibers will contribute as needed.
There is a debate as to whether
muscle can change from one type of muscle fiber to the other but it is
certain that with proper training you can get them to behave more like a
different type. Example: (If you do nothing but run long distances the
Type IIa and IIb will start to behave like a Type I fiber having more
endurance than before the training started.)
There is another
debate as to whether or not your body can actually make new muscle
fibers or if you are born with the same number as you will always have
when you die. To me this really doesn't matter the fact is the more you
work the different types of muscle fibers the better they will work so
get out there and use them.
