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.
Fast-twitch muscles. Fast-twitch muscles use an 'anaerobic' metabolism to create fuel and need more oxygen, and they are much better at generating short bursts of strength or speed than slow muscles, such as a 100 metre sprint or weightlifting, but they tire more quickly.
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.