<prompt> Fast muscle fibers are?RedOxidativeTonicGlycolytic  <response>: Ans. isdi.e., GlycolyticRef: Principles of medicalphysiolog p. 512TYPES OF MUSCLE FIBERS:Two fibers types:Type Ired fibersType IIwhite fibers.Motor unit contains only one muscle fibers type:I.e., All motor unit fibers are either type-I or type II.Hence, named accordingly.CHARACTERISTICS OF MUSCLE FIBER TYPES:ParametersCharacteristicsType I muscle fiberType II muscle fiberDifference according to fiber typeRed -Due to ed myoglobin mitochondrial content.White -Lack myoglobin have few mitochondria.Subtypes- Nil -Type IIA Type IIBIIA - Oxidative glycolytic.IIB - Glycolytic.Usually type IIB fibers refer type II fibers.Other names1. Slow-twitch fibers:Due to small fiber length diameter.Maintain relatively sustained contraction.2. Slow motor unitsHave early recruitment.1. Fast-twitch fibers -Sho duration of twitch.Due to bigger diameter ed myosin actin filaments.Generate greater tension comparatively.2. Type IIaFast Fatigue Resistant FR units:Intermediate fatigability.3. Type IIbFast fatigable units:Late recruitment thresholdMetabolismAerobic.Slow oxidative.Anaerobic.Fast glycolytic.Glycolytic capacity glycogen contentLowHighSarcoplasmic reticulumNormalExtensiveBlood supplyHighNormalMyosin ATPase activityLowHighConduction velocitySlowFastContractile propeiesSlow time to peak tensionType IIa - Fast time to peak tension.Type IIb - Fastest time to peak tension.Type of muscleRed muscles -In muscles required for prolonged contraction.Also with muscles maintaining posture.Back muscles At back of hipGluteus muscles .Calf muscles.WhitePale muscles -Muscles helpful in rapid contractions finer movements.Hand extraocular muscles. 