Like a PP, I used the infant car seat adaptor and starting running/walking with him in it at about 3 months. I also read that 8 months was minimum for running, but quite honestly, I started running with DS at about 5 months. He had excellent head control and I was not offroading in the BOB. We were on residential streets in our neighborhood. He is 11 months old, and has not suffered any damage :) I know many people who have waited until 8 months, but also many more who have started jogging earlier. I think a lot of it depends on your baby's development and your comfort level. Happy running!