A sample response follows: People who utilizes the progression principle will ensure their exercise program increases in frequency, intensity, time, and type. The changes need to happen gradually in order to ensure they make gains in their fitness program. A person who doesn't utilize the progression principle can still gain health benefits from exercising, but will not continue to improve in cardiovascular fitness.
Specifically, some of their most prominent effects occur in the prefrontal cortex—an area involved in mood, cognition, and perception—as well as other regions important in regulating arousal and physiological responses to stress and panic.