I did some running this summer. I learned my lesson years ago about not doing too much the first few times. For my first few runs I was on a track. I'd walk a lap, run a lap, walk another, and that might be it. Maybe I'd add a second running lap. Gradually I strung more running laps together and cut out the walking laps to the first and last laps. I got up to three miles - not fast but steady. Then school started (I'm a teacher) and I haven't been back.