Which of the following statements about slow twitch muscle fibers is true?

Slow twitch muscle fibers, also known as type I fibers, are primarily designed for endurance activities. These fibers are characterized by their ability to contract over long periods without fatiguing quickly. They have a high concentration of mitochondria, which helps in efficiently utilizing oxygen for energy production through aerobic metabolism. This energy production supports activities such as long-distance running or cycling, where sustained efforts are required without the buildup of lactic acid that leads to fatigue.

This focus on aerobic energy systems differentiates slow twitch fibers from fast twitch fibers, which are more suited for short, explosive movements requiring quick bursts of energy but fatigue more rapidly. Consequently, the role of slow twitch fibers in endurance activities highlights their importance in sports and exercises that involve prolonged durations of physical exertion.