How does muscle growth primarily occur?

Muscle growth primarily occurs through hypertrophy of existing muscle fibers, which refers to the increase in the size and cross-sectional area of those fibers rather than the formation of new muscle fibers. Hypertrophy is typically stimulated by resistance training and is influenced by various factors including mechanical tension, metabolic stress, and muscle damage that occur during exercise. These stimuli promote a range of biological responses, leading to the synthesis of new proteins and the enlargement of myofibrils within the muscle cells.

This process is crucial for improving strength and overall muscle performance. While the body has mechanisms to increase muscle fiber number under certain circumstances, such as during extreme conditions or in young individuals, these occurrences are much less common than the hypertrophy of existing fibers. Additionally, muscle fibers do not undergo mitotic division like typical cells; instead, they grow larger and adapt to the demands placed on them through training. Neural adaptations also play a role in initial strength gains by improving the coordination and efficiency of muscle activation but do not contribute directly to muscle fiber growth in the way that hypertrophy does.