If you switch from one form of cardio to the other (read: running to swimming), is it normal to experience weight gain the first week? No changes in diet, just changes in the length of the cardio...by an hour.I went from losing 2lbs a week off of HIIT running 10 minutes every day to gaining a pound this week off of my new swimming workout. The swim workout doesn't feel as intense as the running, but it's still 4000-5000 meters for an hour and a half. I'm 6'1" 175lb. Should I just go back to the HIIT? I frickin hate it after 4 months.