Which statement correctly distinguishes hypertrophy from hyperplasia in skeletal muscle adaptation?

Which statement correctly distinguishes hypertrophy from hyperplasia in skeletal muscle adaptation?

• A. Hyperplasia is enlargement of existing fibers; hypertrophy increases fiber number.
• B. Hypertrophy is enlargement of existing fibers; hyperplasia increases fiber number.
• C. Both hypertrophy and hyperplasia refer to fiber size increases.
• D. Hypertrophy involves increased capillary density.

Answer: (D)

The key idea is distinguishing fiber size from fiber number. Hypertrophy means the existing muscle fibers get bigger, while hyperplasia means there are more muscle fibers (more fibers produced). In skeletal muscle, hypertrophy is the primary adaptive response to resistance training, and hyperplasia, if it occurs, involves increasing fiber count rather than size. Increased capillary density is a vascular adaptation (angiogenesis) that can accompany training to support the bigger or more numerous fibers, but it’s not the defining feature that separates hypertrophy from hyperplasia. So the best distinction is: hypertrophy = enlargement of existing fibers; hyperplasia = increased fiber number.

The key idea is distinguishing fiber size from fiber number. Hypertrophy means the existing muscle fibers get bigger, while hyperplasia means there are more muscle fibers (more fibers produced). In skeletal muscle, hypertrophy is the primary adaptive response to resistance training, and hyperplasia, if it occurs, involves increasing fiber count rather than size. Increased capillary density is a vascular adaptation (angiogenesis) that can accompany training to support the bigger or more numerous fibers, but it’s not the defining feature that separates hypertrophy from hyperplasia. So the best distinction is: hypertrophy = enlargement of existing fibers; hyperplasia = increased fiber number.