P.E Muscle fibre types

-Muscles are composed of thousands and thousands of individual muscle fibres, which are held together by connective tissue.

-Muscles fibres differ in physiological make up and it is the type of fibre that exists which explains, the difference between perfomance in a sprinter and a marathon runner.

-Skeletal muscles have two tpes of fibres: slow twitch and fast twitch fibres.

Slow twitch fibres...

-red

-contract slowly

-aerobic

-enduranced based

-can contract repetively

-exert less force

Fast twitch fibres...

-white

-contract rapidly

-anaerboic

-speed/strength based

-easily exhausted

-exert great force

-Fast twitch and slow twitch fibres vary in different muscles in different individuals.

-the proportion of slow twitch fibres to fast twitch fibres tend to be inherited.

-essentially a marathon runner may have almost 80% slow twitch fibres, which are designed for low intensity, long peiods of work.

-essentially sprinters may have almost 80% fast twitch fibres, which are designed for high intensity, short periods of work because they can generate high force but fatigue easily.

Type 2a

-also referred to as fast oxidative gycolytic fibres.

-they pick up certain type one characteristics through endurance training.

-activities which are fairly high in intensity and of relatively short duration, such as a 200m swim or an 800m run, may well rely on type 2a fibres.

Type 2b fibres...

-pure fast twitch fibres called fast glycolytic.

-they are used for activities with very high intensity.

-have a much stronger force of contraction because the motor neurone that carries the impulse is much larger; there are generally more fibres within a fast twitch motor unit, and the muscle fibres themselves are larger and thicker.

- we would expect a power lifter or a sprinter to possess a large proportion of type 2b fibres.

Slow twitch muscle fibres...

-muscle fibres designed to produce energy aerobically.

-they can produce a relatively small amount of force over a long period of time.

-found in large quantities in the leg muscles of marathon runners and cyclists.

Fast twitch muscle fibres...

-muscle fibres designed to produce energy anaerobically.

-they can produce large amounts of force but only over a short period of time as they fatigue eaily.

-found in large quantities in the leg muscles of 100m sprinters and triple jumpers.

Speed of contraction= slow (110)              Force of contraction= low

Size= smallest                                                 Mitichondrial density= high

Myoglobin content= high                             Fatigability= fatigue resistant

Motor neurone size= small                          Fibres/motor neurone= 10-18

 Anaerobic capacity= low                             Aerobic capacity= high

sarocoplasmic reticulum development= low  

Speed of contraction= fast (50)         Force of contraction= high

Size= high                                             Mitichondrial density= lowest

Myoglobin content= lowest                 Fatigability= less resistant

Motor neurone size= large                 Fibres/motor neurone= 300-800

 Anaerobic capacity= medium             Aerobic capacity= medium

sarocoplasmic reticulum development= high

Speed of contraction= fast (50)          Force of contraction= high

Size= large                                               Mitichondrial density= large

Myoglobin content= low                       Fatigability= easily fatigue

Motor neurone size= large                   Fibres/motor neurone= 300-800

 Anaerobic capacity= high                    Aerobic capacity= low

sarocoplasmic reticulum development= low

- A marathon runner such as Paula Radcliffe will have a high percentage (80-90%) of slow twitch oxidative fibres type one).

-A 100m sprinter such as Asafa Powell will have a high proportion (60-70%) of fast twitch gycolytic muscle fibres (tpye 2b)

-they contain lots of myoglobin which is a structural charactersitc of type 1 fibres.

-they have a well developed blood supply which is a structural charactersitc of a type 1 fibre.

-they have a high aerobic capacity...

-they have a slow speed contraction...

-they have few and small mitochondria, which is a structural characteristic of a type 2b fibres.

-they have more fibres per a motor neurone, which is a structural characterisitc of a type 2b fibre.

-they fatigue quickly

-they contract with more force...

- aerobic exercise- where respiration provides the majority of the energy needed for the activity.

-a good supply of oxgyen is needed.

-exercise is sub-maximal.

-Anaerobic exerice- where anerobic respiration provides the majotity of energy needed for the activity.

-exercise intensity is maximal.

-the duration of the activity is short.

-an individuals mix of muscle fibres type may influence their reasons for choosing to take part in a particular activity because depending on the persons muscle fibres will determined how good they will be at certain activities or sports.

-naturally people are likely to perform in sports in which whay are good or better at because they want to achieve a level of success whether that is personal or elite.