About 35 years ago, I took a gym class that was taught by a very good gym teacher. She is still teaching (but at a different college) so I won't share her name. But the plan was this- walk in two chunks of ten minutes, surrounded by three sets of exercise . Your total "circuit" should take under 40 minutes, but keep moving. You choose the exercises-push ups, squat thrusts, jumping jacks, whatever you like. The key is to do short burst of movement broken up by periods of walking/running/jogging. Sound good to you?