Which training principle focuses on progressively increasing the demands placed on the body?

The principle that focuses on progressively increasing the demands placed on the body is the overload principle. This principle emphasizes that to improve physical performance, stress must be placed on the body in an incrementally greater amount than what it is accustomed to. This can be achieved through increasing the resistance, duration, frequency, or intensity of exercises.

By applying the overload principle, an individual challenges their bodily systems and promotes adaptation, leading to improvements in strength, endurance, and overall fitness. This principle is fundamental in designing training programs, as it ensures continual progress and helps to avoid plateaus in performance. Properly applying this principle ultimately fosters muscle growth, cardiovascular improvements, and enhanced overall fitness levels.