There is no such position as Mayor of the United States (US). A  Mayor is typically a political position for cities and towns. The  United States is led by a president. Curr â¦ ently, the president is  Barack Obama.
Slow twitch muscle fibres are good for endurance activities like long distance running or cycling. They can work for a long time without getting tired. Fast twitch muscles are good for rapid movements like jumping to catch a ball or sprinting for the bus.
Muscle fibers that contract rapidly are known as fast-twitch fibers. Fast-twitch fibers activate and deactivate rapidly and come in two types: Type 2A muscle fibers which fatigue at an intermediate rate, and Type 2B muscle fibers which fatigue rapidly.