Which principle of training refers to the gradual increase of stress placed on the body during exercise?

The principle of training that refers to the gradual increase of stress placed on the body during exercise is progressive overload. This principle is foundational for improving physical fitness and performance, as it emphasizes that in order to enhance muscular strength, endurance, and overall fitness levels, one must progressively increase the demands placed on the body. This can be achieved through various means, such as increasing the weight lifted, enhancing the number of repetitions or sets, extending workout duration, or reducing rest periods between exercises.

By applying progressive overload, the body adapts to increased workloads, which leads to improvements in fitness over time. Without this gradual increase in stress, the body may plateau or stagnate in its development, as it becomes accustomed to the same level of exertion. Thus, this principle is essential for any training program aimed at fostering growth and preventing the risk of injury associated with sudden, excessive increases in activity.