AFAA Personal Trainer Certification Practice Exam

What type of activities are slow twitch fibers primarily used for?

1. High-intensity sprints

2. Maintenance of posture

3. Heavy weight lifting

4. Short-term explosive actions

The correct answer is: Maintenance of posture

Slow twitch fibers, also known as Type I muscle fibers, are primarily used for activities that require sustained endurance and prolonged effort. These fibers are highly resistant to fatigue and are adapted for activities that involve aerobic metabolism, which means they utilize oxygen to generate energy. As a result, they play a crucial role in maintaining posture, support during long-duration activities, and performing lower-intensity exercises over an extended period, such as walking, jogging, and cycling at a steady pace. In contrast, activities that demand quick bursts of power, such as high-intensity sprints, heavy weight lifting, and short-term explosive actions, primarily engage fast twitch fibers (Type II fibers). These fast twitch fibers are more suited for short-duration, high-intensity efforts but fatigue more quickly than slow twitch fibers. Therefore, for tasks focused on maintaining posture and promoting endurance, slow twitch fibers are essential.