Lifehacker Simple 30-40m Full Body Workout
DESCRIPTION20 minutes of cardio (walking or jogging), plus 10 minutes (to start) of strength exercises. Increase the strength rounds by a few minutes every four weeks. No equipment needed.
Choose regular crunches or bicycle crunches. You can also modify regular crunches with reverse crunches (lie on your back and flex your knees, then raise them towards your head).