Type Muscle Fibers
Type I muscle fibers are involved in endurance activities. These fibers, also called
slow twitch fibers, are noted for their ability to produce energy in the presence of oxygen.
Thus, they are primarily aerobic. The main fuel source for this fiber is fats (fatty acids),
which allow the muscle to work at a steady rate with noticeable resistance to fatigue. Their
color is typically quite red, a result of the high content of “myoglobin”, an iron-containing
protein that stores and delivers oxygen. Slow twitch fibers are not noted for their speed,
their anaerobic capacity, or their ability to contract at a fast rate repeatedly, but rather their
indefatigability and aerobic capacity.
Type I muscle fibers are involved in endurance activities. These fibers, also called
slow twitch fibers, are noted for their ability to produce energy in the presence of oxygen.
Thus, they are primarily aerobic. The main fuel source for this fiber is fats (fatty acids),
which allow the muscle to work at a steady rate with noticeable resistance to fatigue. Their
color is typically quite red, a result of the high content of “myoglobin”, an iron-containing
protein that stores and delivers oxygen. Slow twitch fibers are not noted for their speed,
their anaerobic capacity, or their ability to contract at a fast rate repeatedly, but rather their
indefatigability and aerobic capacity.