Here's one idea to try which I read in a magazine wrt running. Do a run/walk combo. If you're doing sprints, this doesn't apply. But, if you want to run further than a mile, try running for 5 minutes and walking, 5 minutes x3. That'll be a 30 minute cardio session. After a week or two when you start feeling comfortable with that, up to 6 min running/4 min walking. Then, 7/3, 8/2, etc. It's a nice slow introduction to doing cardio for 30 minutes.