The principle of progressive overload in resistance training refers to the gradual increase of stress placed on the body during exercise. This can be achieved by increasing the weight, repetitions, or intensity of workouts over time. The goal is to continually challenge the muscles, allowing for adaptations that lead to increased strength, endurance, and muscle size. By progressively overloading the muscles, individuals can avoid plateaus in their training and ensure consistent progress toward their fitness goals. This principle is essential for promoting muscle growth and improving overall physical performance.