Hypertrophy vs. Hyperplasia vs. Myofiber Splitting

Hyperplasia is an increase in the number of muscle fibers.

Hyperplasia occurs primarily during development.

Bodybuilders and powerlifters generally have fewer muscle fibers than average adults.

Animal studies consistently show that hyperplasia occurs in adult muscles.

Hyperplasia is the only mechanism by which adult muscles can become bigger.

Myofiber splitting is a defining characteristic of hypertrophy.

Split myofibers are only found in damaged muscle.

Mechanical load is the primary driver of myofiber splitting.

The majority of strength gains in humans are attributed to hyperplasia.

Hypertrophy is considered more significant than hyperplasia for muscle growth in humans.

Hypertrophy vs. Hyperplasia vs. Myofiber Splitting

Hyperplasia is an increase in the number of muscle fibers. It occurs during development.
Bodybuilders and powerlifters may have more muscle fibers than average adults. This suggests that intensive resistance training can increase the number of muscle fibers.
Some animal studies suggest that hyperplasia can occur, but other studies don't find evidence that adult muscles grow larger due to hyperplasia.
There are controversies and methodological issues regarding hyperplasia in adult muscle growth.

Myofiber Splitting

Myofiber splitting is characterized by branching, fragmentation, or splitting along the length of the muscle fibers.
Split muscle fibers can be found in healthy muscle, but more often in dystrophic muscle and various neuromuscular disorders.
Mechanical stress can cause myofiber splitting. However, the frequency of this is low (less than 1% of fibers). This makes it unlikely to be a major factor in muscle growth.

Bottom Line

Muscle growth in humans is mostly due to the increase in the size of muscle fibers (hypertrophy), rather than an increase in the total number of muscle fibers (hyperplasia) or splitting of the existing muscle fibers.

Explore the differences and similarities between hypertrophy, hyperplasia, and myofiber splitting in muscle physiology. This quiz delves into the mechanisms of muscle growth and the roles that different types of muscle fiber development play in strength training. Test your knowledge on these key concepts surrounding muscle anatomy and growth.