Regarding muscle fiber number, which statement is true?

Regarding muscle fiber number, which statement is true?

• A. Muscle fibers can increase in number through longitudinal splitting
• B. Muscle fibers cannot increase in number
• C. Muscle fibers always increase in number with training
• D. Muscle fibers decrease in number with training

Answer: (B)

Muscle growth from training happens mainly by hypertrophy—existing muscle fibers getting larger as they accumulate more contractile proteins. In humans, the total number of skeletal muscle fibers is generally fixed after development, so resistance training increases size rather than creating new fibers. There are rare or species-specific cases of hyperplasia or occasional fiber splitting, but these are not the typical or reliable adaptations seen in humans. That makes the statement that muscle fibers cannot increase in number the best answer, because the common, well-supported outcome of training is enlargement of existing fibers, not an increase in their count. The other ideas—fiber number increasing with training or decreasing with training—do not align with how human muscles respond to most training programs.

Muscle growth from training happens mainly by hypertrophy—existing muscle fibers getting larger as they accumulate more contractile proteins. In humans, the total number of skeletal muscle fibers is generally fixed after development, so resistance training increases size rather than creating new fibers. There are rare or species-specific cases of hyperplasia or occasional fiber splitting, but these are not the typical or reliable adaptations seen in humans. That makes the statement that muscle fibers cannot increase in number the best answer, because the common, well-supported outcome of training is enlargement of existing fibers, not an increase in their count. The other ideas—fiber number increasing with training or decreasing with training—do not align with how human muscles respond to most training programs.