Certified Personal Trainer (NSCA) Practice Exam

Which option correctly describes the properties of Type 1 and Type II muscle fibers?

1. Type 1 - high force, Type II - slow speed

2. Type 1 - fast speed, Type II - high endurance

3. Type 1 - high endurance, Type II - high force

4. Type 1 - slow speed, Type II - low force

The correct answer is: Type 1 - high endurance, Type II - high force

Type 1 muscle fibers, also known as slow-twitch fibers, are characterized by their high endurance capabilities. They are designed for prolonged activities that require aerobic metabolism, which means they utilize oxygen to produce energy efficiently over long durations. This results in their ability to sustain activity without fatigue for extended periods, making them vital for endurance sports and activities such as long-distance running or cycling. On the other hand, Type II muscle fibers, or fast-twitch fibers, are capable of generating high force but do so at the expense of endurance. These fibers are optimized for explosive and powerful contractions, making them highly effective for short bursts of high-intensity activities such as sprinting or weightlifting. However, they fatigue more quickly than Type 1 fibers due to their reliance on anaerobic metabolism, which does not require oxygen and produces energy more rapidly but cannot be sustained for long periods. This correct option highlights that Type 1 fibers excel in endurance while Type II fibers are better suited for generating high force, capturing the essential differences between these two types of muscle fibers and their respective roles in physical performance.