Final answer:
Transient hypertrophy is the temporary increase in muscle size that occurs during and immediately following a single exercise bout, commonly known as a "pump." It is due to fluid accumulation in the muscle tissue, and should not be confused with long-term muscle growth from resistance training, which involves the increase in muscle mass and cross-sectional area.
Step-by-step explanation:
The hypertrophy referred to in the question is transient hypertrophy, which is the temporary increase in muscle size that occurs during and immediately after a single exercise bout. Unlike chronic hypertrophy, which results from long-term resistance training and leads to an actual increase in the number of sarcomeres and myofibrils within muscle fibers, transient hypertrophy is primarily due to fluid accumulation in the muscle tissue as a response to muscle activity. This phenomenon is also known as a "pump" that bodybuilders often refer to after a workout. To further elaborate, muscular hypertrophy is an increase in muscle mass and cross-sectional area. The increase in dimension is due to an increase in the size (not the number) of individual muscle fibers. This is achieved through the addition of structural proteins and an increase in the number of myofibrils within muscle cells.
Resistance training contributes to hypertrophy partly by causing microscopic damage to muscle fibers, which then repair and adapt by getting larger. This process of damaging and then repairing muscle fibers contributes to muscle strength and mass. Endurance exercise, on the other hand, primarily enhances aerobic capacity and does not lead to significant muscle hypertrophy. In fact, endurance training can lead to an increase in cellular mitochondria, myoglobin and capillary networks, particularly in slow twitch (SO) fibers, rather than causing hypertrophy.