As a parent, there are many things that slip out of my mouth that I desperately wish I hadn't said.

"Yes, you can have more chocolate", is one. "Sure, I'll buy you that drum set", is another.

Lately, I've realised that the thing I say to my kids that I really, really do not mean is this: "Sit down and keep quiet."

It's the catchphrase of the frazzled mum, trying to gather her thoughts or sanity as the little ones run rings around her. Yet, when I seriously think about it, a question bubbles up within me:

Why should they?

Childhood is the time when you definitely should not be sitting down and keeping quiet. It is the season for discovering you are alive and have a body, and what that body can do. Stretch, spring, cavort! Talk, sing, yodel!

Pain and limitations have yet to take hold in young minds. The possibilities of their perfectly calibrated growing bodies are endless.

I remember the gloriousness of just moving when I was a young child. The joy of clambering up, then standing astride, arms akimbo, on the climbing frame in the playground. Racing from the top of my school building to the bottom, and then up again, during recess.

Taking the stairs two, or even three, at a time. Skipping home from the bus interchange, rather than taking the feeder bus.

Even fidgeting on my mother's lap at interminable wedding dinners, while staring at my frilly socks, held a particular pleasure.

Nudging 36, my body is no longer that supple (although weekly Pilates classes are helping to slow down the inevitable; I can now bend and touch my toes).

One night of dancing floors me - in a pathetic, I-can't-move-my-aching- legs way.

I haven't dashed anywhere in ages, because of my weak knees, and also because running makes me feel like my seams are about to split and my insides might end up on the floor. I fear getting a hernia or displacing my womb.

I look at my two sons, aged three and seven, and envy the physical ease with which they explore the world. Run everywhere, I want to tell them. Don't walk. There is so little time, and so much to see and do.

Once a week, I take my elder son to his evening aikido weapons class. There, I watch as he wields a foam sword and spars with his sensei and fellow disciples.

More often than not, he gets bopped on the head or poked in the chest by his opponents. But he is never happier than when he is prancing around in that hour.

Scientists call it the endorphin rush of exercising; I call it every body's propensity to celebrate that it still stands, having survived yet another unpredictable day.

In her new book Kith: The Riddle Of The Childscape, British writer Jay Griffiths makes a case for leaving our kids alone to adventure in the great outdoors.

Trying to put her finger on the malaise in modern children, she concludes that they have, as reviewer Mary Beard puts it in The Guardian, "lost all contact with their kith - with the woods and the wilds, the mountains and moors, the rivers and streams".

What to do when your kith, or homeland, comprises skyscrapers, highways and shopping malls? You move like a hunter, I say. Refuse the socialising command to rest and stay silent.

Childish chatter? It is the last war cry against dumb conformity, and our growing alienation from earth, sky, matter.

Of course, there are times when I do have to coax my kids to stay: in the theatre, in class or, yes, at interminable wedding dinners.

But at home, or as long as they don't make a nuisance of themselves in public, they are free to run everywhere and squeal with glee. Caveat: not on roads or in carparks. Now, run along and be noisy.

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