“How did you do it?” Kelly asks, working her best fake I’m-sooo-happy-for-you-and-your-small-butt smile. “Connor and Bella hate the gym nursery. I’ll never again fit into my pre-mommy Sevens.”

You just smile and say, “These guys have me running around like crazy. It just fell off.”

Sure, if the guys you’re referring to are the staff at the new Cheetah Gym on Broadway, where part of the space is devoted solely to kids (babies through pre-teens). Special trainers will put your brood through their paces on pint-size exercise bikes and tailor-made-for-tots treadmills, while you — this is the good part — sweat in peace. (And don’t think of this as passing your body neurosis on to the next generation, you freaker. It’s simply a smart way to establish healthy exercise habits from the get-go.)

Don’t worry about boredom; they thought of everything. Like networked electronic bikes hooked up to Nintendo racing games. A diaper-free section for tweens. An indoor climbing wall they can all scale a few times before passing out.

But the most family-friendly detail may be the membership prices, which start at $129 a month.

Which is a whole lot cheaper than a new pair of jeans.

Cheetah Gym, 5838 North Broadway, between Hollywood and Rosedale Avenues (773-728-6600 or cheetahgym.com).