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.
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).