Set up before a clock, and every minute on the minute perform 5 pull-ups, 10 push-ups, and 15 squats. Can you continue for thirty minutes? Twenty minutes? How about 10? If you fall behind the clock keep going for thirty minutes, just down grade it to a more manageable rep scheme of, 3 pull-ups, 6 push-ups, 9 squats.
Your score is how many FULL rounds of 5-10-15, you complete on the minute every minute.