what do you call the duration or the length of session of a physical activity?

The duration or length of a session of physical activity is commonly called the "time" or "exercise duration." It refers to the amount of time spent engaging in the physical activity. This term is essential for determining the overall effectiveness and impact of the exercise. In exercise science, time is recognized as one of the key components of exercise prescription, alongside frequency, intensity, and type, often summarized in the FITT principle (Frequency, Intensity, Time, and Type).