Certified Personal Trainer (NSCA) Practice Exam

Which change will increase concentric force production?

1. A. Decreased rate coding

2. B. Increased pennation

3. C. Increased contraction velocity

4. D. Decreased leverage over the joint range of motion

The correct answer is: B. Increased pennation

Increased pennation refers to the angle at which muscle fibers are arranged relative to the direction of the muscle's contraction. Muscles with greater pennation can pack more fibers into a given volume, which allows for a larger cross-sectional area. A larger cross-sectional area contributes to a greater potential for force production because more actin and myosin filaments can interact during contraction. Thus, with increased pennation, there is an enhancement in the overall capacity of the muscle to generate force during concentric contractions. This physiological adaptation is particularly relevant in sports and resistance training, where maximal force output is crucial for performance. Muscles that are more pennated can achieve higher force outputs without an increase in overall muscle size, making this adaptation efficient for strength development. Other factors mentioned, such as rate coding, contraction velocity, and leverage, do not directly contribute to the increase in concentric force production in the same way that increased pennation does. Rate coding relates to the frequency of nerve impulses affecting muscle contraction force, whereas higher contraction velocities typically decrease force output due to the reduced time for cross-bridge cycling. Leverage over the joint range of motion can affect the mechanical advantage of muscles but does not inherently increase the intrinsic force production capabilities of the muscle fibers themselves