What principle states that to improve fitness, one must engage in more physical activity than usual?

The principle that emphasizes the need to engage in more physical activity than usual in order to improve fitness is known as the principle of overload. This principle asserts that in order for the body to adapt and enhance its physiological capabilities—such as strength, endurance, or flexibility—an individual must perform physical activities that exceed their normal daily level of exertion.

This may involve increasing the intensity, duration, frequency, or type of exercise. By applying overload, the body responds by making adaptations that lead to improvements in fitness over time. For instance, lifting heavier weights, increasing running distance, or adding more workout sessions during the week are all examples of applying the overload principle.

Engaging in activity that is beyond what the body is accustomed to encourages adaptations that lead to desired fitness enhancements such as improved cardiovascular health, stronger muscles, and increased endurance. This foundational concept is crucial in designing effective training programs for individuals at any fitness level.