Download Types of Muscle Fibers - Mr-Corrente

Types of Muscle Fibers
Within every skeletal muscle there are two types of fibers: Slow Twitch (Type 1) and
Fast Twitch (Type 2).
Slow Twitch fibers are required for endurance.
Examples: long-distance running, swimming, cycling…
Fast Twitch fibers are required for quick bursts of power and energy.
Examples: sprinting, jumping, weight-lifting…
Slow
Twitch
(Type 1)
Fast
Twitch
(Type 2)
Size
Contraction
Speed
Fatigue
Resistance
Color
Small
Slow
High
Red
Energy
System
Aerobic
(Lots of O2)
Large
Fast
Low
White
Anaerobic
(Little O2)
Mitochondria
Many
Few
Fast Twitch fibers (Type 2) can be further broken down into Type 2a and Type 2b.
Type 2a = Fast Oxidative
These fibers can access both anaerobic and aerobic energy systems, and so are a hybrid of
slow and fast twitch fibers. They produce fast contractions but are less fatigue resistant
than Type 1 fibers.
Type 2b = Fast Glycolytic (Super-fast)
These fibers can only access the anaerobic energy system. They have the fastest
contraction speed but have a very low resistance to fatigue.
Does everyone have the same amount of fast and slow twitch fiber?
Which type of muscle has more slow twitch fibers?
Can training affect muscle fiber type?
Muscle Biopsy under microscope.
Muscle Fiber Composition
Muscle fiber
type
Average
person
Sprint
trained
Aerobic
trained
Slow
(type I)
40%
40%
55%
Fast
(IIa)
50%
20%
40%
Super-fast (IIb)
10%
40%
5%
Fibre type modification
Various types of exercises can bring about changes in the fibres in a skeletal muscle.
Endurance type exercises, such as running or swimming, cause a gradual
transformation of type II B fibres into type II A fibres. The transformed muscle fibres
show a slight increase in diameter, mitochondria, blood capillaries, and
strength. Endurance exercises result in cardiovascular and respiratory changes that
cause skeletal muscles to receive better supplies of oxygen and carbohydrates but do
not contribute to muscle mass. On the other hand, exercises that require great
strength for short periods, such as weight lifting, produce an increase in the size and
strength of type II B fibres. The increase in size is due to increased synthesis of thin
and thick myofilaments. The overall result is that the person develops large muscles.
You can develop your fast-twitch muscle fibre by conducting plyometric or complex
training(combination of plyometrics and weights) to build the fast muscle (IIa) and
performing sprinting types of training to build the super-fast (IIb) to the point where
you can release exercise-induced growth hormone.
The body itself produces the best form of growth hormone. If you want to accelerate
muscle building then use large muscle group targeted weight training in combination
with anaerobic sprinting-types of exercise to increase your body's natural muscle
building steroids.