by Lyle McDonald
Okay. Now that I've sort of covered most of the necessary
info to start a program of aerobic exercise, let me turn my
attention more toward resistance training. Having covered
the various types of machines one might run into and some
basic terminology, let me go into a bit of physiology which
will lead me into a discussion of repetitions.
The only thing I would like to discuss regarding muscular
physiology is the types of muscle fibers and their characteristics.
The differentiation of fiber types will make it a bit easier to
discuss the proper rep ranges for various goals. Let's go.
Type I: Type 1 fibers are the endurance fibers in the body. They
are also known as Slow Oxidative (SO) fibers which helps to
describe them. First and foremost, they have a slow speed of
contraction. This makes them useless for activities (like
sprinting) which requires repetitive fast contraction. However,
they are slow to fatigue which makes them useful for endurance
type athletes. The oxidative part of their name refers to their
mode of energy generation. They continue to contract promarily
through the aerobic oxidation of fats. Type I fibers have a large
amount of mitochondria (the powerhouse of the cell) and few
glycolytic enzymes. They are the smallest fibers size wise and
can generate the least amount of force. Also, they have the least
capacity to get larger when adequately stimulated.
From the above description, we can gather that Type I fibers
are useful for long duration, low intensity activities (like cycling)
and are not the primary target in a muscle building program. This
is true. Generally speaking, bodybuilder types do not have a large
percentage of Type I fibers or they wouldn't have the capacity to
get much larger. A high percentage of SO fibers may be part of
the reason some people (like me) find it almost impossible to gain
any decent amount of muscle. (In any case, it makes a great excuse)
Anyway, how do you go about hitting these muscle fibers. Well, since
they do not fatigue easily, they tend to require many reps at a lower
intensity before being adequately stimulated. Most studies have found
sets in the range of 12-20 repetitions to be optimal. Above 20 reps,
there seems to be a degree of diminishing returns were no additional
stimulation is being recieved.
The second type of fibers is Type II which are subdivided ino type IIA and
IIB.
Type IIB: IIB fibers are the power fibers in the body. They are capable
of generating the most force but fatigue the most quickly. They are able
to contract quickly and rely primarily on glycolysis of carbohydrate
for energy production. They are also called Fast Glycolytic (FG) fibers.
Due to their rapid fatigueability, they are useless for any activity longer
than about 1.5 minutes. These are the largest fibers and have the greatest
potential to grow of the three types. As you would guess, these are the
primary targets for any type of muscle building program.
These fibers seem to respond best to sets in the 4-8 repetition
range.
Type IIA: IIA fibers are the intermediate fibers. They are capable of
both endurance and power although not at the level of either Type I
or IIB. They are also referred to as Fast Oxidative Glycolytic (FOG)
fibers indicating that they contract quickly but can derive their
energy either from the oxidation of fats or the glycolysis of carbs.
They are mid range on size, amount of force production, and potential
to grow. At first glance, these fibers seem kind if useless. However,
these fibers seem to have the greatest ability to shift towards one
end of the spectrum or the other. If you do a lot of endurance training,
the IIA fibers will become more oxidative but if you do lots of
strength/power training, they will become more glycolytic. These
fibers seem to respond to either range of reps but they will shift
towards one type of fiber or the other depending on how they are
stimulated.
Right now I can hear people screaming that they get such and such
of results from high reps or vice versa. Well, that's ok too. Not
everyone will respond to the same thing. Tom Platz, who had some
of the biggest thighs ever, frequently did 30 rep sets of squats which
seems to contradict what I've said. At the outset of this series I tried
to explain that the same thing may not work for the same people, especially
at the more advanced levels. However, for the rank beginner, the above
rep ranges seem to be the best place to start. As they advance, they will
them.
Since this post is getting rather longish, I think I will save the
recommendations for sets and reps for the next post. As always,
mail to lyle…@delphi.com
Lyle
