What does hypertrophy refer to in muscular development?

Hypertrophy refers specifically to the enlargement of muscle fibers in response to various types of training, particularly resistance training. This physiological adaptation occurs as a result of the mechanical overload placed on the muscles, which stimulates muscle protein synthesis and leads to an increase in muscle size. This is essential for athletes or individuals seeking to improve their physical performance, as larger muscles can produce more force.

The other options describe different concepts related to muscular performance. A decrease in muscle size due to inactivity refers to atrophy, which is essentially the opposite of hypertrophy. An increase in muscle strength without a change in size is often a sign of neuromuscular adaptations, where the nervous system becomes more efficient at activating the existing muscle fibers. Lastly, enhanced flexibility of a muscle relates to the ability of a muscle to stretch and move through a range of motion, which is not what hypertrophy entails. Thus, the correct understanding of hypertrophy is crucial for those engaged in fitness and athletic training.