Training with maximal intensity in the 1 to 5 rep range generally promotes which type of hypertrophy?

Training with maximal intensity in the 1 to 5 rep range primarily promotes myofibrillar hypertrophy. This type of hypertrophy is characterized by an increase in the size and density of the muscle fibers’ contractile proteins, primarily actin and myosin. When lifting heavy weights with low repetitions, the focus is on building strength rather than endurance, leading to a greater recruitment of motor units and muscle fibers. This intense training stimulates the body to adapt by increasing the number of myofibrils within the muscle cells, resulting in thicker and stronger muscle fibers.

On the other hand, sarcoplasmic hypertrophy, which involves an increase in the volume of the non-contractile components of the muscle, typically occurs in higher rep ranges with moderate weights. Structural hypertrophy refers to overall increases in muscle size and may include both myofibrillar and sarcoplasmic increases. Functional hypertrophy relates to gains in muscle size with an emphasis on improving performance or specific functional movements. While these other types of hypertrophy have their own methods and benefits, the intensity and rep range specified in the question distinctly align with myofibrillar hypertrophy.