TABLE.

Distinguishing Type I From Type II Muscle Fibers

Muscle Fiber Type	Type I	Type II
Predominant actions	Sustained force Weight-bearing	Sudden movement Purposeful motion
Physiology	Slow twitch	Fast twitch
Predominant myosin (gene)	Slow myosin heavy chain (MHC) (MYH7)	Fast MHC (MYH2)
Typically stain darker	ATPase pH 4.2 Nicotinamide adenine dinucleotide Succinate dehydrogenase Cytochrome C oxidase	ATPase pH 9.4
Glycogen	Less	More (glycolytic metabolism)
Mitochondria	More numerous	Less numerous
Neutral lipid	More (oxidative metabolism)	Less
Meat color (e.g. domestic fowl)	Red (dark)	White

“One mighty slow fat red ox.” Mnemonic used to recall features of type I muscle fibers first learned from mentor Robert Schelper, circa 1984.