We moved into our current apartment about a year ago. We hired a local moving company which did an exceptional job. The two guys they assigned to us worked really hard—we were moving from a two story townhouse to an upstairs apartment, so they hauled three rooms full of furniture downstairs and everything upstairs. We were both amazed at their stamina.

At one point, as I watched one of the movers carry boxes downstairs on his back, I apologized for all the stairs. "We don't mind," he said. "It's like a free gym membership."

I think of that story from time to time—I thought of it yesterday when I took Anna to the park. Her new favorite game is to roll her favorite princess ball up and down the slide. She sits at the top, I bowl it up—it really is like bowling—and she rolls it down. We did that about two hundred times before she got bored.

Then we moved to the swings. Anna loves the swings, but is too young to kick just yet so I have to push her. After about ten minutes on the swings we switched to the see-saw. Anna loves the see saw too, but when she's the only kid, as she often is during a weekday, I get to counterbalance the see saw.

Obviously, I'm way too big to sit on a see saw with her, and bending over to push it with my hands is hard on my back, so I place my foot on the opposite side from her and push the see saw up and down. Fifty reps with one foot, then I switch to the other—just like leg lifts.

So I too have a job with a "free gym membership," and it's by far the most rewarding job I've ever had.