swimming was great when I stopped jogging. Also deep water walking/jogging was great, espec as it took the pressure of my joints. Make sure you listen to your bod hun, I didnt when I was pg with my DS and I am forever questioning if that played a part in his prem birth. I had even just got back from a jog when my waters broke, super fit or not, listen to your body, if you get those pains stop. just spend the rest of your pg maintaining your fitness level not improving it.