Characteristic Type I Fibers Type IIA Fibers Type IIB Fibers
Alternate Name Slow Twitch /Slow Oxidative Fast Twitch / Fast Oxidative Glycolitic (FOG) Fast Twitch / Fast Glycolytic
Speed of Contraction Slow Fast Fast
Endurance High Medium Low
Aerobic Capacity High Medium Low
Capillary Density High Medium Low
Aerobic Enzyme Content High Medium Low
Mitochondria Density High Medium Low
Fatigability Low Medium High
Force Production Low Medium High
Diameter Small Large Largest
Fuel Source Used Fat  Glycogen, Fat  Glycogen
Primary Energy Pathway Used Krebs Krebs &  Glycolysis Glycolysis
Hypertrophy Potential Little Large Largest
Example Activity Used for Running etc. Body Building Power lifting
Recruited First Second Last

 

 

Primary Muscle Proteins: Actin (Thin Filament), Myosin (thick Filament)
Muscle Contraction Theory : "Sliding Filament Theory"
Contractile unit of muscle: Sarcomere
Hypertrophy - Growth of muscle size (primarily responsible for muscle growth)
Hyperplasia - Growth of muscle fiber # (does not occur much in humans)
 
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