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.
From there, you can further categorize fast twitch muscle fiber into Type IIa and Type IIb. Type I Muscle Fibers. Type I muscle fibers have the slowest-contractile speed, the smallest cross-sectional area, the highest oxidative (aerobic) capacity, and the lowest glycolytic (anaerobic) capacity.