Downside of 30 and Getting Tired

Where do four-year-olds get all that energy?  My daughter ran me around the yard a few times yesterday and I was tired!  I need to build some endurance if I am going to keep up with her this summer (and always keep my inhaler on hand). 

I was looking at an elliptical machine, wishing we had room to have some good equipment in the house (that doesn't just collect dust). Our house is too small though.  We walked by some in the store and my daughter said, "Mommy, there is your exercise stuff."  Yeah, in my dreams.