Which type of muscle fibers are primarily used for short bursts of power?

Fast-twitch fibers, also known as Type II fibers, are primarily responsible for generating quick and powerful muscle contractions. These fibers are adapted for anaerobic activity, meaning they can perform at high intensity for short durations without relying on oxygen. This makes them ideal for activities that require sudden bursts of strength or speed, such as sprinting, weightlifting, or quick bursts of energy in sports.

Fast-twitch fibers are characterized by their larger diameter and greater glycogen stores, enabling them to produce more power than slow-twitch fibers. However, they fatigue more quickly than slow-twitch fibers, which are more endurance-focused and suited for prolonged, low-intensity activities. This distinction highlights why fast-twitch fibers are the primary choice for explosive movements that rely on maximum strength over brief time frames.

In contrast, slow-twitch fibers are more efficient for endurance activities and long-distance running because they use oxygen to produce energy and can sustain muscle contractions for extended periods. Intermediate fibers possess characteristics of both types but are not specifically defined as power fibers. Cardiac fibers are specialized muscle tissues found in the heart and are not involved in voluntary movements or quick bursts of power, making them irrelevant in the context of this question.