Progressive overload in training involves:

Progressive overload in training is a fundamental principle that entails gradually increasing the demands placed on the body to enhance fitness levels. This approach aims to stimulate physiological adaptations, encouraging improvements in strength, endurance, flexibility, and overall physical performance. By making training progressively more demanding, whether through increasing weight, intensity, duration, or frequency of workouts, individuals can challenge their bodies beyond their current capabilities, leading to better results and performance improvements over time.

In contrast, the other options do not align with the principle of progressive overload. Increasing rest time or decreasing workout frequency would typically reduce the intensity and overall training stimulus, which may hinder progress rather than promote it. Maintaining the same level of exercise fails to challenge the body and can lead to a plateau in performance, as the body adapts to the existing workload without further adaptation or improvement. Thus, option C correctly captures the essence of how to effectively apply the principle of progressive overload in a training program.