What causes a muscle to twitch?
A muscle twitch is just a single response to a particular stimulus. The twitch can vary considerably according to the type of muscle that that has been stimulated. Basically, there are 3 types of twitch responses based on the 3 types of different fibers being stimulated. If we go in depth we could have reason to argue there are up to 7 different types of fibers, but for this discussion let us stick to the 3 most obvious types of fibers. There are the fast twitch, the slow twitch and the intermediate type. This has to do with the speed of contraction after they have been stimulated from the nerve impulse. The difference between the fast twitch and slow twitch can be quite about 8 times as fast. Fast twitch fibers are located in muscles like the eyeball where our sight depends on speed of contraction and precision of movement. Slow twitch fibers are located mostly in out posture muscles like the back and calves where the muscles need to stay in one place and support the body for a period of time. The fast twitch fibers will hit peak contraction in under 5 mili- seconds. Whereas the slow twitch fiber will take up to 40 mili-seconds to hit full contraction. Most of our muscles contain fibers that are considered to be in the intermediate range and have a contraction rate between 10 and 20 mili-seconds.