Muscle Fibre Types Flashcards
what are the three types of muscle fibres
type I, type IIa, type IIx
what is a type I fibre
slow twitch
what is a type II fibre
fast twitch
what is twitch speed
how quickly a muscle’s cells contract when an impulse arrives
what are the characteristics of type I fibres
- slow twitch
- produce low force
- slow fatiguing
- slow to recover
- oxidative energy source (carbs, fats)
- high blood supply
- red colour
- lots of mitochondria (respiration purposes)
what activities would type I fibres be used for
long duration and lower intensity activities (e.g. marathon, long cycling)
- aerobic energy system
what are the characteristics of type IIa fibres
- fast twitch
- high force production
- medium speed fatiguing
- medium speed recovery
- oxidative and glycotic energy supply
- high blood supply
- red colour
- high mitochondria
what activities would type IIa fibres be used for
moderate duration and moderate intensity activities (e.g. 400m, 100m swim)
- aerobic and lactate energy systems
what are the characteristics of type IIx fibres
- fastest twitch
- very high force production
- fast fatiguing
- fast recovery speed
- glycotic and PC energy supply
- low blood supply
- white colour
- low mitochondria
what activities would type IIx fibres be used for
short duration, high intensity activities (e.g. powerlifting, 60m sprints)
- lactate system and atp-pc energy system
what is hennemann’s size principle
The recruitment of muscle fibres is dependant on the force production required. Muscle recruitment happens type I > type IIa > type IIx as percentage of maximal force increases (as weight gets heavier)
