What type of muscle fibers are resistant to fatigue and contract slowly?

The type of muscle fibers that are resistant to fatigue and contract slowly is known as slow-twitch fibers. These fibers, also referred to as Type I fibers, are characterized by their high endurance and ability to sustain prolonged activity, making them well-suited for endurance activities such as long-distance running or cycling.

Slow-twitch fibers contain a high density of mitochondria, which facilitate aerobic metabolism, allowing for the efficient use of oxygen to produce energy. This energy system supports extended periods of activity without significant fatigue. Additionally, slow-twitch fibers have a rich supply of blood vessels, which enhances oxygen delivery and nutrient exchange.

In comparison, fast-twitch fibers, or Type II fibers, are designed for short bursts of power and speed, but they fatigue more quickly because they primarily rely on anaerobic metabolism. Intermediate fibers, a blend of both types, exhibit characteristics of both slow-twitch and fast-twitch fibers but do not specifically emphasize the fatigue resistance seen in slow-twitch fibers. Contractile fibers is a vague term that does not specifically address the fatigue resistance or speed of contraction.

Understanding the properties of slow-twitch fibers is essential for developing effective training programs that emphasize endurance and longevity in physical performance.