Michelle Obama's toned arms are debated

First Lady Michelle Obama stands tall and regal in her official portrait, a double strand of creamy pearls around her neck, her figure clad in a fitted Michael Kors dress. But there's one aspect of this seemingly benign photograph that's causing something of a commotion, and it lies in that exposed 10-inch-or-so stretch between her shoulder and elbow. The first lady is buff, and she's not afraid to show it.

Her curvy biceps have become something of a lightning rod for remarks from both sexes in a larger discussion of how much female muscle constitutes too much. While some praise Obama as a role model in a world gone obese, others say she's gone too far in displaying the fruit of her workouts. Read one online forum comment: "There is nothing uglier than manly, muscular arms on a woman. Mrs. Obama should be hiding them instead of showing them off."

Even more vitriolic comments have been aimed at Madonna, whose uber-ripped physique is a perennial favorite subject for photographers (the British press reported that her copious hours in the gym factored into the performer's divorce). "Madonna's arms defy logic, actually get grosser," reads one Web headline accompanying a picture of the singer, sleeveless, revealing her sculpted physique.

Why do we care so much? The issue speaks volumes about how men and women view the parameters of femininity and strength.

"In some ways it's kind of an old, tired way of thinking about women and power and boundary policing -- when you can display that power and when you can't, or when it's appropriate," says Sarah Banet-Weiser, an associate professor at the USC Annenberg School for Communication.

The idea of how much muscle is too much is entirely subjective, and people often have a visceral reaction to what they do or don't like. In the Obama-Madonna equation, it's not surprising that few are in the Madonna camp, considering her well-defined build and low body fat, coupled with her age -- few 50-year-old women look like that.

Says personal trainer Ramona Braganza, a member of Gold's Gym Fitness Institute, "She's burning so many calories constantly and her metabolism's sky-high. I'm not being hard on how she looks, but sometimes it's nice to have a little body fat as you get older. It's just healthier looking, and people almost look younger when they do that."