5.c Types of Muscle Fibers

Slow Oxidative (SO)

Contract relatively slow and use aerobic respiration (oxygen and glucose) to produce ATP

Slow Oxidative (SO)

Possess large numbers of mitochondria and are capable of contracting for longer periods because of the large amount of ATP

Slow Oxidative (SO)

Extensively supplied with blood capillaries for O2 supply

Slow Oxidative (SO)

Relatively small diameter and therefore does not produce a large amount of tension

Slow Oxidative (SO)

Possess myoglobin which stores O2 for immediate use

Slow Oxidative (SO)

Useful for maintaining posture, producing isometric contractions, stabilizing bones and joints, and making small movements (not used for powerful fast movements)

Fast Oxidative (FO)

Fast contractions and primarily use aerobic respiration but may switch to anaerobic respiration (glycolysis)

Fast Oxidative (FO)

Produce relatively higher amounts of tension

Fast Oxidative (FO)

Fatigue faster

Fast Oxidative (FO)

Do not possess significant myoglobin (lighter color)

Fast Oxidative (FO)

Use for movements (e.g. walking)

Fast Glycolytic (FG)

Fast contractions and primarily use anaerobic glycolysis

Fast Glycolytic (FG)

Large diameter

Fast Glycolytic (FG)

Possess high amounts of glycogen

Fast Glycolytic (FG)

Fatigue quickest

Fast Glycolytic (FG)

Contain less mitochondria and myoglobin (white color)

Fast Glycolytic (FG)

Used for rapid, forceful contractions for quick, powerful movements