What interval training involves: Basically, you run, jog, or skip ropes (or, mix it up) at a high intensity level (meaning: pushing your heart rate to 80-90% capacity) for 1 minute, then resting for minute, and then doing it again. Do this for 10 times, and your 20-minutes of interval training is done. There are various variants of interval training, all having to do with intensity and time of workout. But, you get the idea about Interval training.
You can easily do this 20-minutes/day, 5 days a week, can't you?