Fast, Slow and Intermediate Fibers
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Intermediate Fibers
Contain little myoglobin and are relatively pale More resistant to fatigue than fast fibers due to extensive capillary network
Hypertrophy
Enlargement of stimulated muscle
Atrophy
Reduction in muscle size due to under stimulation
Slow Fibers
Half diameter of fast fibers Spcialized to continue contractin gfor extended periods Much higher oxygen supply Contain myoglobin Substantial oxygen reserves that can be metabolized during contraction Appear dark red
Fast Fibers
Most skeletal fibers Large diameters and densely packed myofibrils Large glycogen reserves and few mitochondria Fatigue rapidly because contractions use ATP in massive amounts and few mitochondria Prolonged activity supported by anaerobic metabolism
