The author says of Paul Delzer (pictured): "Built like a gymnast, he didn't walk so much as spring. He had a tattoo across his Achilles tendon, so I knew pain was not an issue for him."

After spending the better part of an afternoon in my underwear in front of a relative stranger, I thought I was prepared for anything. But then I met Paul Delzer.

Delzer had returned from six months of travel through Southeast Asia, where he had apparently picked up some new techniques in Cambodia’s killing fields.

“Move your legs like this,” he ordered. Because he’s German, it would be too easy to say he made me goose-step all over the gym, but he did. Then he wrapped my legs in a huge rubber band and made me perform a sideways bunny hop for four lengths of the gym.

“I’m going to pass out,” I gasped after the final lap. “My teeth are buzzing.”

“I’m just testing your motor skills,” he said.

“How are they?”

“Pretty bad.”

Up until this point, I had been feeling pretty good about my progress. I had more energy, was fending off the cold that everyone seemed to be catching, and had noticed that my jeans were getting tight around my developing quad muscles.

But German Paul was insulted by almost everything I did. Built like a gymnast, he didn’t walk so much as spring. He had a tattoo across his Achilles tendon, so I knew pain was not an issue for him.

“Do you run?” he asked.

When I told him yes, he said, “Do you fall?” Then he kicked my right foot to illustrate how it turned inward too much.

“You could do with some tone here,” German Paul said, grabbing the flesh of my upper arm. “And here,” he noted, glancing at my dimpled thigh. “You’re skinny,” he continued, then hesitated.

“I’m skinny fat,” I said, providing the phrase all the women’s magazines use.

“Yes,” he sighed. “I didn’t want to say that, but yes.”

I began seeing German Paul twice a week. I feared and adored him. When I wasn’t sweating in the gym, I was outside pounding the pavement. We ran the stairs of Meridian Hill Park and jogged a three-mile loop around Rock Creek Park, stopping along the way for a few sets of pull-ups on the jungle gym by the zoo. “The last time I ran a mile was in college,” I told him as a way of saying thanks.

I would never have worked this hard on my own. By the end of my second month at Sterling, I not only was physically stronger; I was mentally tougher. I was also pretty addicted to my thrice-weekly routine.

“I’m having a hard time thinking of you as a gym rat,” said my friend Elaine when I met her for coffee dressed in my magical butt pants and tank top.

I began to think of myself as part of some special club. After all, Sterling was an elite place. One day, I worked out next to Paul Wolfowitz (who has a great set of gams). Dermatologist Tina Alster, whom columnist Maureen Dowd (another former client) called the Queen of Lasers, works out there on Saturdays. And former New York Times restaurant critic Frank Bruni wrote about his experiences with Sterling in his memoir, Born Round; he later inscribed Aaron’s copy of his book, “An asshole drill sergeant of the best kind.”

The secret society extended outside the gym. I noticed a woman in my Georgetown neighborhood whose thick blond hair and slightly tanned face looked familiar. As I passed her, she turned and regarded me in the same knowing way, as if we were in our own version of Fight Club.

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