fast and slow twitch fibres: if a dog is born with lots of fast twitch through selective breeding as a greyhound or whippet should be than they use anorobic metabolism, without O2, which means that they produce waste products, such as lactic acid, faster than they can clear them from the muscles but for a short while they are quick. if they have a lot of slow twitch ie a collie then they use aorobic metabolism, with O2, produce less waste products and so can keep the muscles clear and working. a good lamping dog needs a proportion of both for a long nights lamping. the proportion would need to