Bodybuilding - What are Muscles Made Off ?
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. In
general, there are four different fiber types in skeletal muscle. These four
include:
- Type I, also known as
slow-twitch or slow fibers
- Type IIA
- IID
- IIB, also known collectively as fast-twitch or white fibers
- Type IIA
- IID
- IIB, also known collectively as fast-twitch or white fibers
Speed, Size &
Endurance:
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.
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.
Muscle
Contraction:
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!
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!
Fiber
Concentrations:
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 prominantly slow twitch, while the gastrocnemius muscle and the hamstrings are prominantly fast twitch.
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 prominantly slow twitch, while the gastrocnemius muscle and the hamstrings are prominantly 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.
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.
The key to long term progress
in bodybuilding can be summed up by one important word: Variation!
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