it changes based on what exercise i do.
When i was a runner i had more long twitch, i could run literally all day aslong as i drank gatorade and had a mars bar while running, after 2 hours you will have 0 energy otherwise.
Now since iv been on the weights for 2 years i have more fast twitch.
Haha - that's a load of bollocks! You can't genentically change your muscle fibre type depending on what exercise you do - you're born with a certain percentage of fast/slow twitch fibers and you're stuck with them for life.
Have you ever found yourself wondering why turkeys have some dark meat and some white meat? The explanation for the colour differences is pretty simple and has a basis in physiology. The dark meat of the turkey, or chicken, is "red" or slow-twitch muscle. The white meat is "white" or fast-twitch muscle. Most animals have some combination of these two fibre types, though the destinctions may be less obvious. Why are they differently colored? The slow muscles have more mitochondria (full of red pigmented cyctochrome complexes), and more myoglobin packed within the muscle cells. This gives them a darker, reddish color. Humans also have dark and white meat. Some of our muscles, like the soleus in the lower leg are almost all slow twitch fibres. Others such as those controlling eye movements are made up of only fast twitch fibres.
The thing to remember is that fibre type is controlled by the motor nerve that innervates a fibre. Unless you change the nerve, you won't change fibre types from fast to slow or vice versa. Just this type of experiment has been performed in animals (generally rats). There is no compelling evidence to show that human skeletal muscle switches fiber types from "fast" to "slow" due to training.
