For a workout that is hard, fast, and leaves the stress of the day right there on the floor, go for a high-intensity interval training (HIIT) session. "HIIT workouts can be as short as four minutes (like Tabata) or last 30 minutes, and even if you're super tired, you can spare a few. There are so many different types of HIIT routines that at least one will definitely fit your fitness level and needs. You'll be done quickly and feel refreshed," said Chadwell.