What is the primary characteristic of type II muscle fibers?

The primary characteristic of type II muscle fibers is that they are fast-twitch fibers suited for power and speed activities. Type II fibers contract more quickly and with greater force than type I fibers, making them essential for high-intensity tasks that require explosive strength, such as sprinting or heavy lifting. They are designed to generate quick bursts of power but fatigue more rapidly than type I fibers. This is due to their reliance on anaerobic metabolism, which allows for short bursts of energy output but is less efficient for sustained activities.

In contrast, slow-twitch fibers (type I) are more suited for endurance activities and have greater endurance capabilities, enabling them to sustain activities over longer periods. Additionally, type I fibers are ideal for aerobic exercises, where oxygen supply is sufficient to support prolonged efforts, further distinguishing them from the fast-twitch characteristics of type II fibers.