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.
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.