Human Anatomy Classification of skeletal muscle fibers

Fiber property

I: Slow oxidation.

iix: Fast glycolysis

Primary type of catabolism

I: Oxidative.

iix: Glycolytic

Blood supply

I: Extensive.

iix: Limited

Number of mitochondria

I: many.

iix: few

Amount of myoglobin

I: large.

iix: little

Amount of glycogen

I: little.

iix: large

Myosin ATPase activity

I: low.

iix: highest

Fatigability

I: low.

iix: high

Diameter in fiber

I: small to intermediate.

iix: intermediate

Color of muscle

I: red.

iix: light pink to white

Example of activities

I: standing or sitting.

iix: heavy lifting or sprinting