I know my answer should be something like running marathons, or bike riding. In the past it would have been. I am a mom now, and honestly, my favorite physical activity is getting on the floor and playing with my son all day. One of his favorite things is when I put him on my legs and do reverse curls. I always encourage my clients with little kids, and not enough time to do things like this to burn calories! If there kids are anything like my son, they will burn alot!