40 Box or Bench Step ups, 20 per leg
30 Sit ups
20 Push-ups
20 Bent Over Rows

Repeat twice, if you can do three rounds all the better, and time yourself!

Notes: Always finish the repetitions before you move on to the next exercise in the circuit, even if you have to rest for a moment. You can anchor your feet for the sit-ups, push-ups can go to knees - just do them!