Option #4: Go Easy
While fatigue is sometimes specific to the aerobic system, other times it is generalized, taking option three off the table. In these instances, your best choice is to perform a relatively short, low-intensity recovery workout. As you gain experience in training you will learn the difference between how your body feels when it is not ready for high-intensity aerobic training but still able to handle a few sprints and when it is not ready for any high-intensity training. Until you have that experience, default to option three on days when you feel flat, yet not so bad that taking the day off seems like the most sensible option. On some of these occasions you will discover that even your warmup don’t go well. Connecting this experience with how your body felt before you tried the workout will enable you to decide when you just need to go easy in future workouts.