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.
Still, fast-twitch (type IIb) fibers can be converted into moderate fast-twitch (type IIa), or vice versa, through increases in endurance or resistance training. And keep in mind that fast-twitch muscle depletes with age considerably more than slow-twitch, so increasing muscle power is less feasible later in life.he difference might lie in the makeup of their skeletal muscles. People have two general types of skeletal muscle fibers: slow-twitch (type I) and fast-twitch (type II).