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.
Your skeletal muscle contains two types of muscle fibers: fast-twitch and slow-twitch. Your fast-twitch and slow-twitch muscle fibers are separated into three distinct types.Slow-twitch fibers contain type 1 muscle fibers, while your fast twitch fibers contain both type 2a and type 2b.our fast-twitch and slow-twitch muscle fibers are separated into three distinct types. Slow-twitch fibers contain type 1 muscle fibers, while your fast twitch fibers contain both type 2a and type 2b.