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ANTIAGING BODYBUIDLING

TYPES OF MUSCLES

 

Types of Muscles Tissue

There are three types of muscle tissue:

Skeletal – are those muscles attached to bones. This muscle tissue is known as striated; that is, the fibers or cells contain alternating light and dark striations (bands) that are perpendicular to the long axes of the fibers. Skeletal muscle tissue is voluntary; that is, it can be made to contract or relax by conscious control.

Cardiac – striated muscle forming most of the wall of the heart. Its contraction involuntary.

Smooth- located in the walls of hollow internal structures such as blood vessels, the stomach, intestines, uterus and bladder. Smooth muscle fibers are nonstriated and involuntary.
All muscles are prone to hypertrophy. Some smooth muscle fibres, such as those in the uterus, retain their capacity for division and can grow by hyperplasia.


Skeletal Muscles

Skeletal Muscles vary in structure and function. Fibres vary in:

  • colour depending on their oxygen stores [stored in the myoglobin until needed by mitochondria].
  • contraction velocity,
  • their ability to split Adenosine Triphosphate (ATP). Faster contracting fibres have greater ability to split ATP.
  • metabolic process they use to generate ATP.
  • onset of fatigue.

Based on these structural and functional characteristics, skeletal muscle fibres are classified into three types: Type I fibres, Type II B fibres and Type II A fibres.

 

Muscle Characteristic Type I Type IIA Type IIB
Colour Red Red White
Twitch / Contraction Speed Slow Fast Fast
Oxygen Carrying Capacity High High Low
ATP Generation High High Low
ATP Split [Conversion] Slow Slow Fast
Endurance High Med Low
Typically Found Neck Rare in Humans Arms

 

As you can probably work out – some muscles are designed for quick bursts of intense action and others for controlled endurance.

Any fitness program will identify the types of activities you encounter in your normal day and work to develop the right kinds of muscle tissue. For example: fast twitch muscles are needed for the arms in golf and tennis; whilst in these same sports, the legs require endurance in both coupled with quick contraction in tennis.

 

Type of Muscle Loss with Age

Studies have shown that limb muscles from older men and women are 25-35% smaller and have significantly more fat and connective tissue than limb muscles from younger individuals.

Type II [fast-twitch] fibers are smaller in the old, while the size of Type I [slow-twitch] fibers is much less affected.

Significantly smaller total number of muscle fibers

Significantly lower relative Type II fiber area, and a significant increase in Fiber Type I area with increasing age.

These results indicate a gradual decrease in size/volume with advancing age, accompanied by a replacement by fat and connective tissue. This sarcopenia [aging atrophy] appears to be due to a reduction in both number and size of muscle fibers, mainly of Type II, and is to some extent caused by a slowly progressive neurogenic process.


 
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