Name the 3 types of muscle fibres and explain the role of each.

Type I - Slow Twitch (Slow Oxidative)This muscle fibre consists of a large volume of myoglobin (protein used for storing oxygen in the muscles) and mitochondria. As a result they have a high resistance to fatigue and are recruited for aerobic exercise such as long distance running.Type IIa - Fast Twitch (Fast Oxidative)The characteristics of this muscle fibre combine that of type I and II. These too consist of a large number of myoglobin and mitochondria but are not as resistant to fatigue. They can utlitise both aerobic and anaerobic metabolisms and therefore can produce fast strong muscle contractions. Type IIx - Fast Twitch (Fast Glycolytic)This muscle fibre type has a low level of myoglobin and mitrochondria. As a result of this it operates within the anaerobic phase and can produce quick, powerful bursts of speed. However due to this lack of oxygen, fatigue will occur rapidly. This muscle fibre type is used in activities such as sprinting or power lifting.