It is stunning, the dervish-like recyclable energy that is a child.

I mean, look, I’m no slouch. I stay up late, get up early and generally know how to shake it. There’s precious little time spent eating bon-bons in half-recline on the chaise lounge.

That said, my daughters are tuned to a higher pitch entirely. So driven are they to move that nearly everything on their Christmas wish lists had wheels. Adding Santa’s contributions to what we already had, we now lay claim to bikes, scooters, roller blades, roller shoes, roller skates and a funky little contraption called The Flying Turtle. And nothing gathers dust.

This doesn’t make for entirely restful parenting. One of our girls is long and gangly and capable of tripping herself up, and the other moves through her days at mock speed with an apparently limitless pain threshold. The wild one makes my dad so nervous that he’d like to see her don protective gear before breakfast and stay armored until bathtime each night. Come to think of it, a helmet in the tub might be a good idea, too.

My parents were with us at Christmastime, witness to a lot of movement, and plucky participants in an ungodly bit of it themselves. If we weren’t rolling, we were running. If we weren’t skating, we were climbing. And somehow, on the off moments, crafts were crafted, board games strategized and well-rehearsed variety shows pulled off.

Mom and Dad spent two nights at a hotel and the girls devoted their visits to the glass elevators that were “fancier and faster than the Plaza’s” (nevermind that this was an Embassy Suites).

Is it any wonder that the drive-through lane at Starbucks is host to more than a few gasping mamas in mini-vans?

So we went away together – my husband and I, our kids and their grandparents – to a stone cabin on the Medina River, for a few days of hill hiking, dam building and deer watching. And, just our luck, the road was unpaved so wheeled footware was deemed temporarily obsolete.

While there, on one uncharacteristically mellow, stocking-footed evening by the fire, Mom pulled out some old audio tapes – from when our girls were toddlers and, thirty-some years earlier, my sister and I. Funny treasures, these – sweet croaky little voices lacking linguistically correct s’s and r’s. Off-key renditions of Twinkle, Twinkle and Happy Birthday, dramatic re-tellings of A Day in the Life of a Preschooler.

We were enraptured, all of us, listening to these compelling little strangers. And that was the odd part – my daughters were just as foreign to me as my own child-self, just as distant and unfamiliar. Merely a few dozen months ago, I embodied those voices like heartbeats and now they belong to a tape machine, an ancient and rickety technology itself. If we don’t capture them as MP3s while we can, they’ll be gone for good.

Looking over at my mom and dad listening to me at age five, I see them swallow over the same lump in their throats, the fleeting movement of their children. And here I sit, almost 40, nostalgic for my own babes already.

Now, about that protective gear…