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.
Your muscles operate in three basic movements: eccentric, concentric and isometric. Weight training and most cardiovascular exercises incorporate both eccentric and concentric motions. Concentric motions occur when your muscles are shortened and eccentric motions involve the lengthening of your muscles.