National Academy of Sports Medicine (NASM) Group Fitness Instructor Practice Exam

Which resistance training protocol is most effective for promoting muscular hypertrophy?

1. Low repetition ranges

2. Intermediate repetition ranges

3. High repetition ranges

4. Single set protocols

The correct answer is: Intermediate repetition ranges

Promoting muscular hypertrophy, which is the increase in the size of muscle fibers, is most effectively achieved through intermediate repetition ranges. This approach typically involves using a moderate load (around 67-85% of one-rep max) and performing approximately 6 to 12 repetitions per set. This repetition range strikes a balance between the amount of weight lifted and the total volume of work performed, which is essential for muscle growth. The moderate intensity allows for sufficient tension on the muscles while also promoting metabolic stress, both of which are key factors in triggering the physiological responses necessary for hypertrophy. Muscle fibers, particularly Type II fibers, are optimally recruited within this range, leading to increased muscle damage and subsequent recovery processes that contribute to growth. Additionally, intermediate repetition ranges facilitate adequate time under tension, which is another crucial element for stimulating muscle growth. While low repetition ranges can be useful for building strength, and high repetition ranges can improve muscular endurance, neither approach is as effective as the moderate repetition range for maximizing hypertrophy. Single set protocols, while time-efficient, may not provide enough volume or intensity to fully stimulate muscle growth, making the intermediate repetition range the preferred choice for achieving hypertrophy goals.