Sweatpants stepped out of the gym and onto the runway at Isabel Marant’s Fall ’10 show. Sonia by Sonia Rykiel’s take on the trend is slim and slightly tapered—in other words, miles away from your baggy track suit. Pair them with a ladylike blouse and trim blazer for a touch of twenty-first-century preppy chic. Click the image to shop.

-Laura Wasson