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.
Humans have three different types of muscle fibers: slow-twitch (Type I), fast-twitch A (Type IIa), and fast-twitch B (Type IIb). Type I muscle fibers are recruited for aerobic activities, so therefore contract slowly, but are very resistant to fatigue.