What is the difference between slow twitch and fast twitch muscle fibres?

Slow oxidative fibres are designed for aerobic endurance exercise. They use oxygen to work at a moderate rate over a long period. They are red due to the high concentration of blood vessels which deliver a rich supply of oxygenated blood. They have a high resistance to fatigue and are found in high percentages in athletes such as marathon runners.

Fast twitch fibres are designed for anaerobic exercise. They produce small amounts of energy very quickly. Unlike slow twitch they don't use oxygen to produce energy (ATP) so do not require such a rich blood supply. This means they are white in colur not red. They fatigue much more quickly than slow twitch fibres. Athletes in high power sports such as sprinting have high percentages of fast twitch fibres.