The principle of progressive overload in exercise training refers to the gradual increase of stress placed on the body during workouts. By systematically increasing the weights, repetitions, or intensity of exercises, individuals can promote continuous muscle adaptation and growth. This principle is crucial for improving strength and endurance over time. Without progressive overload, the body adapts to a static routine and plateaus, hindering fitness improvement. Therefore, incorporating this principle keeps workouts challenging and aligned with fitness goals.