What characterizes slow twitch muscle fibers?

Slow twitch muscle fibers, also known as Type I fibers, are primarily characterized by their ability to support endurance activities. These fibers possess a high concentration of myoglobin, which enhances their oxygen storage capacity and allows them to utilize aerobic metabolism efficiently. This means they can sustain prolonged periods of activity without fatigue, making them ideal for endurance exercises like long-distance running, cycling, and swimming.

Their endurance-oriented nature is due to their slower contraction speed and the greater number of mitochondria within, enabling sustained energy production. Additionally, they have a rich supply of capillaries that further supports oxygen delivery to the muscle, facilitating prolonged use during moderate-intensity activities. This distinct physical profile is what makes slow twitch fibers essential for athletes and individuals engaging in activities that require longevity and stamina rather than short bursts of power.