Muscle Movements  For the following movements, identify the major joint movements and the muscle responsible

Muscle tissue Muscle fibre type

Fibre types  Skeletal muscle can be distinguished on the basis of the speed of contraction  Type 1 – slow twitch  Type 2 – fast twitch  Human body contains both types

Fibre type determination – how its done

Type I fibres Type II fibres

Muscle fibre type Muscle Fibre Type Slow twitch (Type 1) Fast Twitch (Type II) Type IIa (Intermediate) Type IIb (True fast twitch)

Slow twitch fibres (Type I)  Characteristics: More capillaries per muscle fibre than fast twitch therefore have a better blood supplyMore capillaries per muscle fibre than fast twitch therefore have a better blood supply More myoglobin than fast twitch fibresMore myoglobin than fast twitch fibres Myoglobin is a store for oxygenMyoglobin is a store for oxygen Red in colour due to the large amount of myoglobin (red pigment)Red in colour due to the large amount of myoglobin (red pigment) More mitochondria (ATP producers) and aerobic energy producing enzymesMore mitochondria (ATP producers) and aerobic energy producing enzymes

 Result? Slower contraction time than fast twitchSlower contraction time than fast twitch A greater ability to use oxygen known as oxidative potential so they are sometimes called SLOW OXIDATIVE or SO fibresA greater ability to use oxygen known as oxidative potential so they are sometimes called SLOW OXIDATIVE or SO fibres

Fast Twitch Fibres (Type IIa + IIb)  General characteristics: Low aerobic capacity due to low numbers of capillaries, smaller blood supply and smaller mitochondria than slow twitch.Low aerobic capacity due to low numbers of capillaries, smaller blood supply and smaller mitochondria than slow twitch. Have high levels of glycolytic enzymes (anaerobic energy producing enzymes)Have high levels of glycolytic enzymes (anaerobic energy producing enzymes) High ability to produce energy anaerobically by the glycolytic system.High ability to produce energy anaerobically by the glycolytic system.

Fast twitch type IIa - intermediate  Characteristics: Pink in colour due to moderately high levels of myoglobin.Pink in colour due to moderately high levels of myoglobin. Has high levels of oxidative and glycolytic enzymes.Has high levels of oxidative and glycolytic enzymes. A moderately well developed ability for aerobic and anaerobic energy productionA moderately well developed ability for aerobic and anaerobic energy production Faster contraction speed than slow twitch.Faster contraction speed than slow twitch.  Result? Because of their moderate contraction speed and high levels of oxidative and glycolytic enzymes type IIa fibres are often referred to as FOG (Fast oxidative glycolytic)Because of their moderate contraction speed and high levels of oxidative and glycolytic enzymes type IIa fibres are often referred to as FOG (Fast oxidative glycolytic)

Fast Twitch type IIb – true fast twitch  Characteristics: Low levels of mitochondriaLow levels of mitochondria White in colour due to very low levels of myoglobinWhite in colour due to very low levels of myoglobin Poor capacity for aerobic energy production.Poor capacity for aerobic energy production. High levels of glycolytic enzymes.High levels of glycolytic enzymes. Very high capacity for anaerobic energy production.Very high capacity for anaerobic energy production.  Result? Because of their fast contraction speed and their high levels of glycolytic enzymes type Iib fibres are often referred to as FAST GLYCOLYTIC or FG fibresBecause of their fast contraction speed and their high levels of glycolytic enzymes type Iib fibres are often referred to as FAST GLYCOLYTIC or FG fibres

Muscle fibre type and contraction velocity

Type 1 Type 2a Type 2b RedRedWhite Contract slowly Contract rapidly (but not as fast as type 2b) Contract rapidly AerobicAerobicAnaerobic Endurance-based such as cycling and long-distance running Middle-distance such as ice skating Speed and strength-based such as sprinting and rugby Can contract repeatedly Fairly resistant to fatigue Easily exhausted Exert minimal force Exert medium Exert great force

Types of sport  All types are used in all types of exercise  Type 1 particularly adapted to low-intensity aerobic endurance work  particularly at the beginning of exercise, regardless of intensity  Type 2 fibres adapt to high intensity anaerobic exercise  Also employed during low intensity workouts as you fatigue

Muscle fibre type and sports performance  Nature vs nurture?  Is sporting potential determined before we are born?  E.g. sprinters and long distance/endurance sports

Think about it  Every athlete in the 100m Olympic final in 2004 was of African-Caribbean descent.  Is this coincidence or do African- Caribbean athletes possess an advantage in their type 2 concentrations?