20 min tabata with pullups

Do 4 min for each exercise:
 -20 seconds on: do as many reps as possible
 -10 seconds off: rest

With these exercises:
-pullups
-pushups
-situps
-squats

Do not rest longer than a minute between exercises.

You can do this with different similar exercises, but this is the one I do. The only way to get the most out of this is to push yourself. Make goals and try to beat them.