Final answer:
The progression from simpler to more challenging exercise in terms of intensity, duration, or frequency is known as progressive overload, which is key for improving fitness and strength.
Step-by-step explanation:
The progression from a lower intensity level to a higher intensity level, longer duration, and/or increased frequency of exercise is known as progressive overload. This principle involves increasing the intensity of exercise, the frequency of workouts, and/or altering the target muscles or activities to continually challenge the body and stimulate improvements in physical fitness and muscle strength.
For effective strength training, for instance, one must continually increase the intensity by lifting heavier weights to promote muscle growth. A pattern of physical exercise that involves some short periods of vigorous muscular work and longer periods of medium and varied muscular work can help in progressively overloading the muscles.
Similarly, aerobic exercises such as running, swimming, cycling, and walking, should also involve gradual increases in intensity or duration to improve cardiovascular endurance. The goal is to ensure that the muscles and cardiovascular system are sufficiently challenged to adapt to higher levels of exertion, leading to an improvement in overall fitness and performance.