What describes the process of muscle fibers splitting?

The process of muscle fibers splitting is termed hyperplasia. This phenomenon refers to the increase in the number of muscle fibers, which occurs as a response to specific types of exercise and muscle strain. When muscles are subjected to certain stimuli, such as resistance training, they can undergo a process where the existing muscle fibers replicate and divide, leading to an increase in both the quantity and potentially the overall strength of the muscle tissue.

Hypertrophy, while related to muscle growth, specifically refers to the enlargement of existing muscle fibers rather than an increase in their number. Atrophy, on the other hand, involves a decrease in muscle mass and size due to disuse, injury, or illness, and myopathy describes a disease of muscle tissue that can impact muscle function but does not involve the splitting of muscle fibers. Therefore, hyperplasia accurately captures the process described in the question.