Like no one else, Oscar Smith knows what supermodels need. As a trainer to some of the top girls in the business, it's his job to tend to the models' bodies—even if it sometimes means showing up at their apartments to drag them to the gym. A former gymnast (he trained for the 1988 Olympics but had to bow out due to a knee injury), the 43-year-old works out of an exclusive 1,500-square-foot gym in the luxe condo building One York. Though his clients also include Tom Brady ("in the off season"), David Blaine ("for his stunts"), Amanda Bynes and Ed Burns, it's those long-legged, tiny torsoed living clothes hangers he specializes in. We checked in with Smith right as Fashion Week kicked off.

Catherine McNeil in the Dsquared2 fall 2009 runway show.

How did all the models start flocking to your gym?
I started with Petra [Nemcova], and then after she survived the tsunami [in 2004], she told people, "My trainer and all the stuff I'd been doing working out-wise kept me alive." Then, boom! Selita Ebanks, Caroline Winberg, model after model. 

And your gym itself, which is so private—
Yes, they like that they don't have to be bothered. A lot of girls would tell me horror stories—they go into an Equinox or a Crunch and they always get a guy who hits on them, who's annoying them, or they just feel like all eyes are on them.

Describe the workouts you have them do.
It's pretty much all the same. I hate to say it, but [models] are not that great when it comes to cardio shape. Forty-five to fifty minutes of a straight, straight, no-stop workout routine exhausts them completely. We do traditional Muay Thai kickboxing, or we'll do a cardio day where we'll run on the West Side Highway and in between do push-ups and sit-ups. I have a pool, so we'll also do mini-triathlons. We do high reps with light weights and we do mat work which is a mixture of yoga and Pilates.

From left: Selita Ebanks and Caroline Winberg.

Which models are you working with this week?
Catherine McNeil, Anna J, Rianne ten Haken, Maxine—don't ask me her last time because it's in German!—Marta, another one, Brazilian, I can't pronounce it.

Is it hard to motivate such a genetically blessed species?
It is, they'll find every excuse! They'll say, "I walked to my casting, isn't that exercise?" or "I just had an apple today." You know, a lot of the models were actually athletes in high school, and they know what it's like to work out—they just get lazy. If they don't show up, I'll go their apartments.

Since most of them don't need to lose much weight, what are you working on exactly?
There's such a thing as skinny fat. The girls are so thin, but they have not an ounce of muscle and their skin sags all over their body. A lot of girls want to stay toned, like a Charlize Theron, but not get too athletic.

Do you only work out supermodels, or is it possible for a mortal to train with you too?
Yes, I charge $150 an hour. And that goes for everyone. Whether you're a doctor, a lawyer, a superstar or a mommy, you're all treated the same way. But the models do get a special rate.

See Oscar Smith's website at O-diesel.com

See our interviews with the industry's top models in "The Skinny"

Photos: models, WWD Staff.