On what does the recommended time (duration) of an endurance training workout depend? Frequency specificity intensity mode

The correct answer is intensity.

The intensity signifies towards the extent of energy exhausted at the time of performing exercise. The intensity differs with each individual. It has been observed that intensity possess an influence on what fuel the body utilizes and what kind of changes the body makes after performing exercise.

It is the concentration of the physical power, which the body utilizes at the time of doing an activity. For example, the intensity of the exercise illustrates how hard the body has to function to walk a kilometer in twenty minutes.