I have gone running twice so far. The first time, I ran 2 kilometers in 15 minutes, at a run-to-walk ratio of 2:1 (1 minute running, 30 seconds walking.) It was not very difficult, but I forgot to stretch before running so I was sore the day after. The second time, I ran 4 kilometers in 30 minutes, increasing the ratio to 5:1 (2.5 min. running, .5 min. walking.) I remembered to warm up and stretch before and after, which improved my experience substantially.