The invention is directed to systems and methods that can determine a user's fitness based on a single factor such as oxygen lung volume (pmVO2). A heart rate measurement is conducted on the user after the user performs a physical test specified by a fitness application of the system. The heart rate measurement is converted into a pmVO2 value and compared to pmVO2 values of other individuals. The system assigns the user a fitness grade based on the comparison result. The system further includes an artificial intelligent system that helps the user to move from a grade to a higher grade.
