Muscle Physiology
- Oh Those Crazy Muscles!
When the average person takes a look at a
bodybuilder all he sees is a series of lumps and bumps of
varying shapes and sizes. Upon inspection he may find these
odd protrusions to be fascinating, cool, or perhaps
grotesquemaybe even a little intimidating. But little does he
know how complex and intricate all these "lumps" really
are!
Let's take a look inside these lumps, see what
they are made of and what we can do to make them bigger and
stronger. Ok, first let me stop calling them lumps or bumps
and refer to them more properly as skeletal muscles, or just
muscles for short.
Muscle is composed of
bundles of muscle fibers or myofibers. Each fiber is composed
of myofibrils, which, in turn, are composed of myofilaments.
The myofilaments are made up of two proteins called myosin and
actin. The myosin and actin act within the smallest functional
unit of muscle, the sarcomere, to produce a contraction. It is
the myosin protein, however, which holds the key to the
differences in muscle fiber types. (Complicated lumps these
muscles, aren't they!) In general, there are four different
fiber types in skeletal muscle. These four include: Type I,
also known as slow-twitch or red fibers; Type IIA, IID, and
IIB, also known collectively as fast-twitch or white
fibers.
Type I are the slowest, smallest,
and have the highest level of endurance of all the fibers.
Next come the Type IIA, IID, and finally the Type IIB, which
are the fastest, largest, and least endurance oriented in the
group.
As you contract a muscle, you'll
recruit those muscle fibers in a specific order. The smallest
(lowest threshold) fibers, the Type I, are recruited first. As
the speed or force of contraction is increased, you will
sequentially recruit the Type IIA, IID, and IIB muscle fibers.
However, to recruit the Type IIB fibers it may take over 90%
of a maximal contraction!
All people are
born with these muscle fiber types. Most muscles contain
almost an even split of slow (Type I) and fast (Type II)
fibers. There are a few exceptions, however, as the soleus
muscle of the calf is predominantly slow twitch, while the
gastrocnemius muscle and the hamstrings are predominantly fast
twitch. Also, individuals on opposite ends of the athletic
spectrum like sprinters and marathon runners for example, may
possess a higher percentage of one fiber
type.
So what does this mean to all of us
bodybuilders? Well, in order to obtain maximal muscle size we
must regularly train all of our muscle fibers. A combination
of bodybuilding (higher and lower rep), powerlifting, and even
a little Olympic-style lifting may be best. Bodybuilding seems
to stress the Type I and IIA fibers, while the IIB fibers may
be best stimulated through powerlifting and Olympic lifting.
The IID fibers are perhaps stressed equally by all three forms
of training. I believe that the key to long term progress in
bodybuilding can be summed up by one important word:
VARIATION!
Doing the same three sets of
8-12 reps over and over will help you to a point. But after
that, make a change! By selectively alternating your training
volume (total sets/reps), training intensity (weight lifted),
training techniques (forced reps, pre-exhaust, supersets, drop
sets, etc.), training tempo (rep speed), rest between sets,
bodypart arrangement, etc., you're more likely to avoid
injuries and overtraining and therefore maximize your gains.
As long as the stimulus presented to your muscles is novel and
taxing, they will continue to adapt
accordingly.
Just remember that your muscle
fibers are not static entitiesthey are dynamic and malleable.
Therefore you yourself should not be static-don't do the same
thing over and over and expect a different result. Don't get
stuck in just one type of training program! Be creative! Be
dynamic! Your muscles will reward you with continuous gains in
size, strength, and endurance. Now, go get to work on those
"lumps!"
Eric Broser (gopro on the forums): Moderater of
training, diet & nutrition, and supplementation on
IronMagazineForums.com, is available for online personal
training, dietary guidance, and contest prep coaching. For
details send him a e-mail
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