A 100 m sprinter needs a huge amount of ATP very quickly, far faster than oxygen can be delivered to the muscles. Sprinting therefore depends mainly on anaerobic sources of ATP.For the first few seconds, ATP is regenerated from creatine phosphate, which transfers its phosphate to ADP. This store is small and runs out in around 10 seconds. After that, glycolysis followed by lactate production supplies ATP rapidly, at the cost of lactate build-up.Sprinters' muscles contain a high proportion of fast-twitch fibres, adapted for rapid, powerful contraction:
• many glycolytic enzymes and large stores of glycogen and creatine phosphate;
• few mitochondria and little myoglobin, so they look pale (white muscle);
• few capillaries;
• an extensive sarcoplasmic reticulum, so calcium ions are released quickly;
• they contract quickly but fatigue quickly.Endurance athletes such as marathon runners have more slow-twitch fibres. These have many mitochondria, lots of myoglobin (red muscle) and a dense capillary network, so they respire mainly aerobically, contract more slowly and resist fatigue.The proportion of each fibre type is largely inherited, but training changes fibre properties. Sprint training increases the size of fast-twitch fibres and improves the muscle's ability to tolerate and clear lactate.
• many glycolytic enzymes and large stores of glycogen and creatine phosphate;
• few mitochondria and little myoglobin, so they look pale (white muscle);
• few capillaries;
• an extensive sarcoplasmic reticulum, so calcium ions are released quickly;
• they contract quickly but fatigue quickly.Endurance athletes such as marathon runners have more slow-twitch fibres. These have many mitochondria, lots of myoglobin (red muscle) and a dense capillary network, so they respire mainly aerobically, contract more slowly and resist fatigue.The proportion of each fibre type is largely inherited, but training changes fibre properties. Sprint training increases the size of fast-twitch fibres and improves the muscle's ability to tolerate and clear lactate.